Port RecyclerView to com.android.internal.widget.RecyclerView
Change-Id: I5d5912fee6f736bfc93d28ad53fc35e22be953c3
diff --git a/core/java/com/android/internal/widget/RecyclerView.java b/core/java/com/android/internal/widget/RecyclerView.java
new file mode 100644
index 0000000..0cf3164
--- /dev/null
+++ b/core/java/com/android/internal/widget/RecyclerView.java
@@ -0,0 +1,12255 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.internal.widget;
+
+import android.annotation.CallSuper;
+import android.annotation.IntDef;
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.content.Context;
+import android.content.res.TypedArray;
+import android.database.Observable;
+import android.graphics.Canvas;
+import android.graphics.Matrix;
+import android.graphics.PointF;
+import android.graphics.Rect;
+import android.graphics.RectF;
+import android.os.Build;
+import android.os.Bundle;
+import android.os.Parcel;
+import android.os.Parcelable;
+import android.os.SystemClock;
+import android.os.Trace;
+import android.util.AttributeSet;
+import android.util.Log;
+import android.util.SparseArray;
+import android.util.TypedValue;
+import android.view.AbsSavedState;
+import android.view.Display;
+import android.view.FocusFinder;
+import android.view.InputDevice;
+import android.view.MotionEvent;
+import android.view.VelocityTracker;
+import android.view.View;
+import android.view.ViewConfiguration;
+import android.view.ViewGroup;
+import android.view.ViewParent;
+import android.view.accessibility.AccessibilityEvent;
+import android.view.accessibility.AccessibilityManager;
+import android.view.accessibility.AccessibilityNodeInfo;
+import android.view.animation.Interpolator;
+import android.widget.EdgeEffect;
+import android.widget.OverScroller;
+
+import com.android.internal.R;
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.widget.RecyclerView.ItemAnimator.ItemHolderInfo;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.ref.WeakReference;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * A flexible view for providing a limited window into a large data set.
+ *
+ * <h3>Glossary of terms:</h3>
+ *
+ * <ul>
+ * <li><em>Adapter:</em> A subclass of {@link Adapter} responsible for providing views
+ * that represent items in a data set.</li>
+ * <li><em>Position:</em> The position of a data item within an <em>Adapter</em>.</li>
+ * <li><em>Index:</em> The index of an attached child view as used in a call to
+ * {@link ViewGroup#getChildAt}. Contrast with <em>Position.</em></li>
+ * <li><em>Binding:</em> The process of preparing a child view to display data corresponding
+ * to a <em>position</em> within the adapter.</li>
+ * <li><em>Recycle (view):</em> A view previously used to display data for a specific adapter
+ * position may be placed in a cache for later reuse to display the same type of data again
+ * later. This can drastically improve performance by skipping initial layout inflation
+ * or construction.</li>
+ * <li><em>Scrap (view):</em> A child view that has entered into a temporarily detached
+ * state during layout. Scrap views may be reused without becoming fully detached
+ * from the parent RecyclerView, either unmodified if no rebinding is required or modified
+ * by the adapter if the view was considered <em>dirty</em>.</li>
+ * <li><em>Dirty (view):</em> A child view that must be rebound by the adapter before
+ * being displayed.</li>
+ * </ul>
+ *
+ * <h4>Positions in RecyclerView:</h4>
+ * <p>
+ * RecyclerView introduces an additional level of abstraction between the {@link Adapter} and
+ * {@link LayoutManager} to be able to detect data set changes in batches during a layout
+ * calculation. This saves LayoutManager from tracking adapter changes to calculate animations.
+ * It also helps with performance because all view bindings happen at the same time and unnecessary
+ * bindings are avoided.
+ * <p>
+ * For this reason, there are two types of <code>position</code> related methods in RecyclerView:
+ * <ul>
+ * <li>layout position: Position of an item in the latest layout calculation. This is the
+ * position from the LayoutManager's perspective.</li>
+ * <li>adapter position: Position of an item in the adapter. This is the position from
+ * the Adapter's perspective.</li>
+ * </ul>
+ * <p>
+ * These two positions are the same except the time between dispatching <code>adapter.notify*
+ * </code> events and calculating the updated layout.
+ * <p>
+ * Methods that return or receive <code>*LayoutPosition*</code> use position as of the latest
+ * layout calculation (e.g. {@link ViewHolder#getLayoutPosition()},
+ * {@link #findViewHolderForLayoutPosition(int)}). These positions include all changes until the
+ * last layout calculation. You can rely on these positions to be consistent with what user is
+ * currently seeing on the screen. For example, if you have a list of items on the screen and user
+ * asks for the 5<sup>th</sup> element, you should use these methods as they'll match what user
+ * is seeing.
+ * <p>
+ * The other set of position related methods are in the form of
+ * <code>*AdapterPosition*</code>. (e.g. {@link ViewHolder#getAdapterPosition()},
+ * {@link #findViewHolderForAdapterPosition(int)}) You should use these methods when you need to
+ * work with up-to-date adapter positions even if they may not have been reflected to layout yet.
+ * For example, if you want to access the item in the adapter on a ViewHolder click, you should use
+ * {@link ViewHolder#getAdapterPosition()}. Beware that these methods may not be able to calculate
+ * adapter positions if {@link Adapter#notifyDataSetChanged()} has been called and new layout has
+ * not yet been calculated. For this reasons, you should carefully handle {@link #NO_POSITION} or
+ * <code>null</code> results from these methods.
+ * <p>
+ * When writing a {@link LayoutManager} you almost always want to use layout positions whereas when
+ * writing an {@link Adapter}, you probably want to use adapter positions.
+ *
+ * @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_layoutManager
+ */
+public class RecyclerView extends ViewGroup implements ScrollingView, NestedScrollingChild {
+
+ static final String TAG = "RecyclerView";
+
+ static final boolean DEBUG = false;
+
+ private static final int[] NESTED_SCROLLING_ATTRS = { android.R.attr.nestedScrollingEnabled };
+
+ private static final int[] CLIP_TO_PADDING_ATTR = {android.R.attr.clipToPadding};
+
+ /**
+ * On Kitkat and JB MR2, there is a bug which prevents DisplayList from being invalidated if
+ * a View is two levels deep(wrt to ViewHolder.itemView). DisplayList can be invalidated by
+ * setting View's visibility to INVISIBLE when View is detached. On Kitkat and JB MR2, Recycler
+ * recursively traverses itemView and invalidates display list for each ViewGroup that matches
+ * this criteria.
+ */
+ static final boolean FORCE_INVALIDATE_DISPLAY_LIST = Build.VERSION.SDK_INT == 18
+ || Build.VERSION.SDK_INT == 19 || Build.VERSION.SDK_INT == 20;
+ /**
+ * On M+, an unspecified measure spec may include a hint which we can use. On older platforms,
+ * this value might be garbage. To save LayoutManagers from it, RecyclerView sets the size to
+ * 0 when mode is unspecified.
+ */
+ static final boolean ALLOW_SIZE_IN_UNSPECIFIED_SPEC = Build.VERSION.SDK_INT >= 23;
+
+ static final boolean POST_UPDATES_ON_ANIMATION = Build.VERSION.SDK_INT >= 16;
+
+ /**
+ * On L+, with RenderThread, the UI thread has idle time after it has passed a frame off to
+ * RenderThread but before the next frame begins. We schedule prefetch work in this window.
+ */
+ private static final boolean ALLOW_THREAD_GAP_WORK = Build.VERSION.SDK_INT >= 21;
+
+ /**
+ * FocusFinder#findNextFocus is broken on ICS MR1 and older for View.FOCUS_BACKWARD direction.
+ * We convert it to an absolute direction such as FOCUS_DOWN or FOCUS_LEFT.
+ */
+ private static final boolean FORCE_ABS_FOCUS_SEARCH_DIRECTION = Build.VERSION.SDK_INT <= 15;
+
+ /**
+ * on API 15-, a focused child can still be considered a focused child of RV even after
+ * it's being removed or its focusable flag is set to false. This is because when this focused
+ * child is detached, the reference to this child is not removed in clearFocus. API 16 and above
+ * properly handle this case by calling ensureInputFocusOnFirstFocusable or rootViewRequestFocus
+ * to request focus on a new child, which will clear the focus on the old (detached) child as a
+ * side-effect.
+ */
+ private static final boolean IGNORE_DETACHED_FOCUSED_CHILD = Build.VERSION.SDK_INT <= 15;
+
+ static final boolean DISPATCH_TEMP_DETACH = false;
+ public static final int HORIZONTAL = 0;
+ public static final int VERTICAL = 1;
+
+ public static final int NO_POSITION = -1;
+ public static final long NO_ID = -1;
+ public static final int INVALID_TYPE = -1;
+
+ /**
+ * Constant for use with {@link #setScrollingTouchSlop(int)}. Indicates
+ * that the RecyclerView should use the standard touch slop for smooth,
+ * continuous scrolling.
+ */
+ public static final int TOUCH_SLOP_DEFAULT = 0;
+
+ /**
+ * Constant for use with {@link #setScrollingTouchSlop(int)}. Indicates
+ * that the RecyclerView should use the standard touch slop for scrolling
+ * widgets that snap to a page or other coarse-grained barrier.
+ */
+ public static final int TOUCH_SLOP_PAGING = 1;
+
+ static final int MAX_SCROLL_DURATION = 2000;
+
+ /**
+ * RecyclerView is calculating a scroll.
+ * If there are too many of these in Systrace, some Views inside RecyclerView might be causing
+ * it. Try to avoid using EditText, focusable views or handle them with care.
+ */
+ static final String TRACE_SCROLL_TAG = "RV Scroll";
+
+ /**
+ * OnLayout has been called by the View system.
+ * If this shows up too many times in Systrace, make sure the children of RecyclerView do not
+ * update themselves directly. This will cause a full re-layout but when it happens via the
+ * Adapter notifyItemChanged, RecyclerView can avoid full layout calculation.
+ */
+ private static final String TRACE_ON_LAYOUT_TAG = "RV OnLayout";
+
+ /**
+ * NotifyDataSetChanged or equal has been called.
+ * If this is taking a long time, try sending granular notify adapter changes instead of just
+ * calling notifyDataSetChanged or setAdapter / swapAdapter. Adding stable ids to your adapter
+ * might help.
+ */
+ private static final String TRACE_ON_DATA_SET_CHANGE_LAYOUT_TAG = "RV FullInvalidate";
+
+ /**
+ * RecyclerView is doing a layout for partial adapter updates (we know what has changed)
+ * If this is taking a long time, you may have dispatched too many Adapter updates causing too
+ * many Views being rebind. Make sure all are necessary and also prefer using notify*Range
+ * methods.
+ */
+ private static final String TRACE_HANDLE_ADAPTER_UPDATES_TAG = "RV PartialInvalidate";
+
+ /**
+ * RecyclerView is rebinding a View.
+ * If this is taking a lot of time, consider optimizing your layout or make sure you are not
+ * doing extra operations in onBindViewHolder call.
+ */
+ static final String TRACE_BIND_VIEW_TAG = "RV OnBindView";
+
+ /**
+ * RecyclerView is attempting to pre-populate off screen views.
+ */
+ static final String TRACE_PREFETCH_TAG = "RV Prefetch";
+
+ /**
+ * RecyclerView is attempting to pre-populate off screen itemviews within an off screen
+ * RecyclerView.
+ */
+ static final String TRACE_NESTED_PREFETCH_TAG = "RV Nested Prefetch";
+
+ /**
+ * RecyclerView is creating a new View.
+ * If too many of these present in Systrace:
+ * - There might be a problem in Recycling (e.g. custom Animations that set transient state and
+ * prevent recycling or ItemAnimator not implementing the contract properly. ({@link
+ * > Adapter#onFailedToRecycleView(ViewHolder)})
+ *
+ * - There might be too many item view types.
+ * > Try merging them
+ *
+ * - There might be too many itemChange animations and not enough space in RecyclerPool.
+ * >Try increasing your pool size and item cache size.
+ */
+ static final String TRACE_CREATE_VIEW_TAG = "RV CreateView";
+ private static final Class<?>[] LAYOUT_MANAGER_CONSTRUCTOR_SIGNATURE =
+ new Class[]{Context.class, AttributeSet.class, int.class, int.class};
+
+ private final RecyclerViewDataObserver mObserver = new RecyclerViewDataObserver();
+
+ final Recycler mRecycler = new Recycler();
+
+ private SavedState mPendingSavedState;
+
+ /**
+ * Handles adapter updates
+ */
+ AdapterHelper mAdapterHelper;
+
+ /**
+ * Handles abstraction between LayoutManager children and RecyclerView children
+ */
+ ChildHelper mChildHelper;
+
+ /**
+ * Keeps data about views to be used for animations
+ */
+ final ViewInfoStore mViewInfoStore = new ViewInfoStore();
+
+ /**
+ * Prior to L, there is no way to query this variable which is why we override the setter and
+ * track it here.
+ */
+ boolean mClipToPadding;
+
+ /**
+ * Note: this Runnable is only ever posted if:
+ * 1) We've been through first layout
+ * 2) We know we have a fixed size (mHasFixedSize)
+ * 3) We're attached
+ */
+ final Runnable mUpdateChildViewsRunnable = new Runnable() {
+ @Override
+ public void run() {
+ if (!mFirstLayoutComplete || isLayoutRequested()) {
+ // a layout request will happen, we should not do layout here.
+ return;
+ }
+ if (!mIsAttached) {
+ requestLayout();
+ // if we are not attached yet, mark us as requiring layout and skip
+ return;
+ }
+ if (mLayoutFrozen) {
+ mLayoutRequestEaten = true;
+ return; //we'll process updates when ice age ends.
+ }
+ consumePendingUpdateOperations();
+ }
+ };
+
+ final Rect mTempRect = new Rect();
+ private final Rect mTempRect2 = new Rect();
+ final RectF mTempRectF = new RectF();
+ Adapter mAdapter;
+ @VisibleForTesting LayoutManager mLayout;
+ RecyclerListener mRecyclerListener;
+ final ArrayList<ItemDecoration> mItemDecorations = new ArrayList<>();
+ private final ArrayList<OnItemTouchListener> mOnItemTouchListeners =
+ new ArrayList<>();
+ private OnItemTouchListener mActiveOnItemTouchListener;
+ boolean mIsAttached;
+ boolean mHasFixedSize;
+ @VisibleForTesting boolean mFirstLayoutComplete;
+
+ // Counting lock to control whether we should ignore requestLayout calls from children or not.
+ private int mEatRequestLayout = 0;
+
+ boolean mLayoutRequestEaten;
+ boolean mLayoutFrozen;
+ private boolean mIgnoreMotionEventTillDown;
+
+ // binary OR of change events that were eaten during a layout or scroll.
+ private int mEatenAccessibilityChangeFlags;
+ boolean mAdapterUpdateDuringMeasure;
+
+ private final AccessibilityManager mAccessibilityManager;
+ private List<OnChildAttachStateChangeListener> mOnChildAttachStateListeners;
+
+ /**
+ * Set to true when an adapter data set changed notification is received.
+ * In that case, we cannot run any animations since we don't know what happened until layout.
+ *
+ * Attached items are invalid until next layout, at which point layout will animate/replace
+ * items as necessary, building up content from the (effectively) new adapter from scratch.
+ *
+ * Cached items must be discarded when setting this to true, so that the cache may be freely
+ * used by prefetching until the next layout occurs.
+ *
+ * @see #setDataSetChangedAfterLayout()
+ */
+ boolean mDataSetHasChangedAfterLayout = false;
+
+ /**
+ * This variable is incremented during a dispatchLayout and/or scroll.
+ * Some methods should not be called during these periods (e.g. adapter data change).
+ * Doing so will create hard to find bugs so we better check it and throw an exception.
+ *
+ * @see #assertInLayoutOrScroll(String)
+ * @see #assertNotInLayoutOrScroll(String)
+ */
+ private int mLayoutOrScrollCounter = 0;
+
+ /**
+ * Similar to mLayoutOrScrollCounter but logs a warning instead of throwing an exception
+ * (for API compatibility).
+ * <p>
+ * It is a bad practice for a developer to update the data in a scroll callback since it is
+ * potentially called during a layout.
+ */
+ private int mDispatchScrollCounter = 0;
+
+ private EdgeEffect mLeftGlow, mTopGlow, mRightGlow, mBottomGlow;
+
+ ItemAnimator mItemAnimator = new DefaultItemAnimator();
+
+ private static final int INVALID_POINTER = -1;
+
+ /**
+ * The RecyclerView is not currently scrolling.
+ * @see #getScrollState()
+ */
+ public static final int SCROLL_STATE_IDLE = 0;
+
+ /**
+ * The RecyclerView is currently being dragged by outside input such as user touch input.
+ * @see #getScrollState()
+ */
+ public static final int SCROLL_STATE_DRAGGING = 1;
+
+ /**
+ * The RecyclerView is currently animating to a final position while not under
+ * outside control.
+ * @see #getScrollState()
+ */
+ public static final int SCROLL_STATE_SETTLING = 2;
+
+ static final long FOREVER_NS = Long.MAX_VALUE;
+
+ // Touch/scrolling handling
+
+ private int mScrollState = SCROLL_STATE_IDLE;
+ private int mScrollPointerId = INVALID_POINTER;
+ private VelocityTracker mVelocityTracker;
+ private int mInitialTouchX;
+ private int mInitialTouchY;
+ private int mLastTouchX;
+ private int mLastTouchY;
+ private int mTouchSlop;
+ private OnFlingListener mOnFlingListener;
+ private final int mMinFlingVelocity;
+ private final int mMaxFlingVelocity;
+ // This value is used when handling generic motion events.
+ private float mScrollFactor = Float.MIN_VALUE;
+ private boolean mPreserveFocusAfterLayout = true;
+
+ final ViewFlinger mViewFlinger = new ViewFlinger();
+
+ GapWorker mGapWorker;
+ GapWorker.LayoutPrefetchRegistryImpl mPrefetchRegistry =
+ ALLOW_THREAD_GAP_WORK ? new GapWorker.LayoutPrefetchRegistryImpl() : null;
+
+ final State mState = new State();
+
+ private OnScrollListener mScrollListener;
+ private List<OnScrollListener> mScrollListeners;
+
+ // For use in item animations
+ boolean mItemsAddedOrRemoved = false;
+ boolean mItemsChanged = false;
+ private ItemAnimator.ItemAnimatorListener mItemAnimatorListener =
+ new ItemAnimatorRestoreListener();
+ boolean mPostedAnimatorRunner = false;
+ RecyclerViewAccessibilityDelegate mAccessibilityDelegate;
+ private ChildDrawingOrderCallback mChildDrawingOrderCallback;
+
+ // simple array to keep min and max child position during a layout calculation
+ // preserved not to create a new one in each layout pass
+ private final int[] mMinMaxLayoutPositions = new int[2];
+
+ private final int[] mScrollOffset = new int[2];
+ private final int[] mScrollConsumed = new int[2];
+ private final int[] mNestedOffsets = new int[2];
+
+ /**
+ * These are views that had their a11y importance changed during a layout. We defer these events
+ * until the end of the layout because a11y service may make sync calls back to the RV while
+ * the View's state is undefined.
+ */
+ @VisibleForTesting
+ final List<ViewHolder> mPendingAccessibilityImportanceChange = new ArrayList();
+
+ private Runnable mItemAnimatorRunner = new Runnable() {
+ @Override
+ public void run() {
+ if (mItemAnimator != null) {
+ mItemAnimator.runPendingAnimations();
+ }
+ mPostedAnimatorRunner = false;
+ }
+ };
+
+ static final Interpolator sQuinticInterpolator = new Interpolator() {
+ @Override
+ public float getInterpolation(float t) {
+ t -= 1.0f;
+ return t * t * t * t * t + 1.0f;
+ }
+ };
+
+ /**
+ * The callback to convert view info diffs into animations.
+ */
+ private final ViewInfoStore.ProcessCallback mViewInfoProcessCallback =
+ new ViewInfoStore.ProcessCallback() {
+ @Override
+ public void processDisappeared(ViewHolder viewHolder, @NonNull ItemHolderInfo info,
+ @Nullable ItemHolderInfo postInfo) {
+ mRecycler.unscrapView(viewHolder);
+ animateDisappearance(viewHolder, info, postInfo);
+ }
+ @Override
+ public void processAppeared(ViewHolder viewHolder,
+ ItemHolderInfo preInfo, ItemHolderInfo info) {
+ animateAppearance(viewHolder, preInfo, info);
+ }
+
+ @Override
+ public void processPersistent(ViewHolder viewHolder,
+ @NonNull ItemHolderInfo preInfo, @NonNull ItemHolderInfo postInfo) {
+ viewHolder.setIsRecyclable(false);
+ if (mDataSetHasChangedAfterLayout) {
+ // since it was rebound, use change instead as we'll be mapping them from
+ // stable ids. If stable ids were false, we would not be running any
+ // animations
+ if (mItemAnimator.animateChange(viewHolder, viewHolder, preInfo, postInfo)) {
+ postAnimationRunner();
+ }
+ } else if (mItemAnimator.animatePersistence(viewHolder, preInfo, postInfo)) {
+ postAnimationRunner();
+ }
+ }
+ @Override
+ public void unused(ViewHolder viewHolder) {
+ mLayout.removeAndRecycleView(viewHolder.itemView, mRecycler);
+ }
+ };
+
+ public RecyclerView(Context context) {
+ this(context, null);
+ }
+
+ public RecyclerView(Context context, @Nullable AttributeSet attrs) {
+ this(context, attrs, 0);
+ }
+
+ public RecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
+ super(context, attrs, defStyle);
+ if (attrs != null) {
+ TypedArray a = context.obtainStyledAttributes(attrs, CLIP_TO_PADDING_ATTR, defStyle, 0);
+ mClipToPadding = a.getBoolean(0, true);
+ a.recycle();
+ } else {
+ mClipToPadding = true;
+ }
+ setScrollContainer(true);
+ setFocusableInTouchMode(true);
+
+ final ViewConfiguration vc = ViewConfiguration.get(context);
+ mTouchSlop = vc.getScaledTouchSlop();
+ mMinFlingVelocity = vc.getScaledMinimumFlingVelocity();
+ mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
+ setWillNotDraw(getOverScrollMode() == View.OVER_SCROLL_NEVER);
+
+ mItemAnimator.setListener(mItemAnimatorListener);
+ initAdapterManager();
+ initChildrenHelper();
+ // If not explicitly specified this view is important for accessibility.
+ if (getImportantForAccessibility() == View.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
+ setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
+ }
+ mAccessibilityManager = (AccessibilityManager) getContext()
+ .getSystemService(Context.ACCESSIBILITY_SERVICE);
+ setAccessibilityDelegateCompat(new RecyclerViewAccessibilityDelegate(this));
+ // Create the layoutManager if specified.
+
+ boolean nestedScrollingEnabled = true;
+
+ if (attrs != null) {
+ int defStyleRes = 0;
+ TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RecyclerView,
+ defStyle, defStyleRes);
+ String layoutManagerName = a.getString(R.styleable.RecyclerView_layoutManager);
+ int descendantFocusability = a.getInt(
+ R.styleable.RecyclerView_descendantFocusability, -1);
+ if (descendantFocusability == -1) {
+ setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
+ }
+ a.recycle();
+ createLayoutManager(context, layoutManagerName, attrs, defStyle, defStyleRes);
+
+ if (Build.VERSION.SDK_INT >= 21) {
+ a = context.obtainStyledAttributes(attrs, NESTED_SCROLLING_ATTRS,
+ defStyle, defStyleRes);
+ nestedScrollingEnabled = a.getBoolean(0, true);
+ a.recycle();
+ }
+ } else {
+ setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
+ }
+
+ // Re-set whether nested scrolling is enabled so that it is set on all API levels
+ setNestedScrollingEnabled(nestedScrollingEnabled);
+ }
+
+ /**
+ * Returns the accessibility delegate compatibility implementation used by the RecyclerView.
+ * @return An instance of AccessibilityDelegateCompat used by RecyclerView
+ */
+ public RecyclerViewAccessibilityDelegate getCompatAccessibilityDelegate() {
+ return mAccessibilityDelegate;
+ }
+
+ /**
+ * Sets the accessibility delegate compatibility implementation used by RecyclerView.
+ * @param accessibilityDelegate The accessibility delegate to be used by RecyclerView.
+ */
+ public void setAccessibilityDelegateCompat(
+ RecyclerViewAccessibilityDelegate accessibilityDelegate) {
+ mAccessibilityDelegate = accessibilityDelegate;
+ setAccessibilityDelegate(mAccessibilityDelegate);
+ }
+
+ /**
+ * Instantiate and set a LayoutManager, if specified in the attributes.
+ */
+ private void createLayoutManager(Context context, String className, AttributeSet attrs,
+ int defStyleAttr, int defStyleRes) {
+ if (className != null) {
+ className = className.trim();
+ if (className.length() != 0) { // Can't use isEmpty since it was added in API 9.
+ className = getFullClassName(context, className);
+ try {
+ ClassLoader classLoader;
+ if (isInEditMode()) {
+ // Stupid layoutlib cannot handle simple class loaders.
+ classLoader = this.getClass().getClassLoader();
+ } else {
+ classLoader = context.getClassLoader();
+ }
+ Class<? extends LayoutManager> layoutManagerClass =
+ classLoader.loadClass(className).asSubclass(LayoutManager.class);
+ Constructor<? extends LayoutManager> constructor;
+ Object[] constructorArgs = null;
+ try {
+ constructor = layoutManagerClass
+ .getConstructor(LAYOUT_MANAGER_CONSTRUCTOR_SIGNATURE);
+ constructorArgs = new Object[]{context, attrs, defStyleAttr, defStyleRes};
+ } catch (NoSuchMethodException e) {
+ try {
+ constructor = layoutManagerClass.getConstructor();
+ } catch (NoSuchMethodException e1) {
+ e1.initCause(e);
+ throw new IllegalStateException(attrs.getPositionDescription()
+ + ": Error creating LayoutManager " + className, e1);
+ }
+ }
+ constructor.setAccessible(true);
+ setLayoutManager(constructor.newInstance(constructorArgs));
+ } catch (ClassNotFoundException e) {
+ throw new IllegalStateException(attrs.getPositionDescription()
+ + ": Unable to find LayoutManager " + className, e);
+ } catch (InvocationTargetException e) {
+ throw new IllegalStateException(attrs.getPositionDescription()
+ + ": Could not instantiate the LayoutManager: " + className, e);
+ } catch (InstantiationException e) {
+ throw new IllegalStateException(attrs.getPositionDescription()
+ + ": Could not instantiate the LayoutManager: " + className, e);
+ } catch (IllegalAccessException e) {
+ throw new IllegalStateException(attrs.getPositionDescription()
+ + ": Cannot access non-public constructor " + className, e);
+ } catch (ClassCastException e) {
+ throw new IllegalStateException(attrs.getPositionDescription()
+ + ": Class is not a LayoutManager " + className, e);
+ }
+ }
+ }
+ }
+
+ private String getFullClassName(Context context, String className) {
+ if (className.charAt(0) == '.') {
+ return context.getPackageName() + className;
+ }
+ if (className.contains(".")) {
+ return className;
+ }
+ return RecyclerView.class.getPackage().getName() + '.' + className;
+ }
+
+ private void initChildrenHelper() {
+ mChildHelper = new ChildHelper(new ChildHelper.Callback() {
+ @Override
+ public int getChildCount() {
+ return RecyclerView.this.getChildCount();
+ }
+
+ @Override
+ public void addView(View child, int index) {
+ RecyclerView.this.addView(child, index);
+ dispatchChildAttached(child);
+ }
+
+ @Override
+ public int indexOfChild(View view) {
+ return RecyclerView.this.indexOfChild(view);
+ }
+
+ @Override
+ public void removeViewAt(int index) {
+ final View child = RecyclerView.this.getChildAt(index);
+ if (child != null) {
+ dispatchChildDetached(child);
+ }
+ RecyclerView.this.removeViewAt(index);
+ }
+
+ @Override
+ public View getChildAt(int offset) {
+ return RecyclerView.this.getChildAt(offset);
+ }
+
+ @Override
+ public void removeAllViews() {
+ final int count = getChildCount();
+ for (int i = 0; i < count; i++) {
+ dispatchChildDetached(getChildAt(i));
+ }
+ RecyclerView.this.removeAllViews();
+ }
+
+ @Override
+ public ViewHolder getChildViewHolder(View view) {
+ return getChildViewHolderInt(view);
+ }
+
+ @Override
+ public void attachViewToParent(View child, int index,
+ ViewGroup.LayoutParams layoutParams) {
+ final ViewHolder vh = getChildViewHolderInt(child);
+ if (vh != null) {
+ if (!vh.isTmpDetached() && !vh.shouldIgnore()) {
+ throw new IllegalArgumentException("Called attach on a child which is not"
+ + " detached: " + vh);
+ }
+ if (DEBUG) {
+ Log.d(TAG, "reAttach " + vh);
+ }
+ vh.clearTmpDetachFlag();
+ }
+ RecyclerView.this.attachViewToParent(child, index, layoutParams);
+ }
+
+ @Override
+ public void detachViewFromParent(int offset) {
+ final View view = getChildAt(offset);
+ if (view != null) {
+ final ViewHolder vh = getChildViewHolderInt(view);
+ if (vh != null) {
+ if (vh.isTmpDetached() && !vh.shouldIgnore()) {
+ throw new IllegalArgumentException("called detach on an already"
+ + " detached child " + vh);
+ }
+ if (DEBUG) {
+ Log.d(TAG, "tmpDetach " + vh);
+ }
+ vh.addFlags(ViewHolder.FLAG_TMP_DETACHED);
+ }
+ }
+ RecyclerView.this.detachViewFromParent(offset);
+ }
+
+ @Override
+ public void onEnteredHiddenState(View child) {
+ final ViewHolder vh = getChildViewHolderInt(child);
+ if (vh != null) {
+ vh.onEnteredHiddenState(RecyclerView.this);
+ }
+ }
+
+ @Override
+ public void onLeftHiddenState(View child) {
+ final ViewHolder vh = getChildViewHolderInt(child);
+ if (vh != null) {
+ vh.onLeftHiddenState(RecyclerView.this);
+ }
+ }
+ });
+ }
+
+ void initAdapterManager() {
+ mAdapterHelper = new AdapterHelper(new AdapterHelper.Callback() {
+ @Override
+ public ViewHolder findViewHolder(int position) {
+ final ViewHolder vh = findViewHolderForPosition(position, true);
+ if (vh == null) {
+ return null;
+ }
+ // ensure it is not hidden because for adapter helper, the only thing matter is that
+ // LM thinks view is a child.
+ if (mChildHelper.isHidden(vh.itemView)) {
+ if (DEBUG) {
+ Log.d(TAG, "assuming view holder cannot be find because it is hidden");
+ }
+ return null;
+ }
+ return vh;
+ }
+
+ @Override
+ public void offsetPositionsForRemovingInvisible(int start, int count) {
+ offsetPositionRecordsForRemove(start, count, true);
+ mItemsAddedOrRemoved = true;
+ mState.mDeletedInvisibleItemCountSincePreviousLayout += count;
+ }
+
+ @Override
+ public void offsetPositionsForRemovingLaidOutOrNewView(
+ int positionStart, int itemCount) {
+ offsetPositionRecordsForRemove(positionStart, itemCount, false);
+ mItemsAddedOrRemoved = true;
+ }
+
+ @Override
+ public void markViewHoldersUpdated(int positionStart, int itemCount, Object payload) {
+ viewRangeUpdate(positionStart, itemCount, payload);
+ mItemsChanged = true;
+ }
+
+ @Override
+ public void onDispatchFirstPass(AdapterHelper.UpdateOp op) {
+ dispatchUpdate(op);
+ }
+
+ void dispatchUpdate(AdapterHelper.UpdateOp op) {
+ switch (op.cmd) {
+ case AdapterHelper.UpdateOp.ADD:
+ mLayout.onItemsAdded(RecyclerView.this, op.positionStart, op.itemCount);
+ break;
+ case AdapterHelper.UpdateOp.REMOVE:
+ mLayout.onItemsRemoved(RecyclerView.this, op.positionStart, op.itemCount);
+ break;
+ case AdapterHelper.UpdateOp.UPDATE:
+ mLayout.onItemsUpdated(RecyclerView.this, op.positionStart, op.itemCount,
+ op.payload);
+ break;
+ case AdapterHelper.UpdateOp.MOVE:
+ mLayout.onItemsMoved(RecyclerView.this, op.positionStart, op.itemCount, 1);
+ break;
+ }
+ }
+
+ @Override
+ public void onDispatchSecondPass(AdapterHelper.UpdateOp op) {
+ dispatchUpdate(op);
+ }
+
+ @Override
+ public void offsetPositionsForAdd(int positionStart, int itemCount) {
+ offsetPositionRecordsForInsert(positionStart, itemCount);
+ mItemsAddedOrRemoved = true;
+ }
+
+ @Override
+ public void offsetPositionsForMove(int from, int to) {
+ offsetPositionRecordsForMove(from, to);
+ // should we create mItemsMoved ?
+ mItemsAddedOrRemoved = true;
+ }
+ });
+ }
+
+ /**
+ * RecyclerView can perform several optimizations if it can know in advance that RecyclerView's
+ * size is not affected by the adapter contents. RecyclerView can still change its size based
+ * on other factors (e.g. its parent's size) but this size calculation cannot depend on the
+ * size of its children or contents of its adapter (except the number of items in the adapter).
+ * <p>
+ * If your use of RecyclerView falls into this category, set this to {@code true}. It will allow
+ * RecyclerView to avoid invalidating the whole layout when its adapter contents change.
+ *
+ * @param hasFixedSize true if adapter changes cannot affect the size of the RecyclerView.
+ */
+ public void setHasFixedSize(boolean hasFixedSize) {
+ mHasFixedSize = hasFixedSize;
+ }
+
+ /**
+ * @return true if the app has specified that changes in adapter content cannot change
+ * the size of the RecyclerView itself.
+ */
+ public boolean hasFixedSize() {
+ return mHasFixedSize;
+ }
+
+ @Override
+ public void setClipToPadding(boolean clipToPadding) {
+ if (clipToPadding != mClipToPadding) {
+ invalidateGlows();
+ }
+ mClipToPadding = clipToPadding;
+ super.setClipToPadding(clipToPadding);
+ if (mFirstLayoutComplete) {
+ requestLayout();
+ }
+ }
+
+ /**
+ * Returns whether this RecyclerView will clip its children to its padding, and resize (but
+ * not clip) any EdgeEffect to the padded region, if padding is present.
+ * <p>
+ * By default, children are clipped to the padding of their parent
+ * RecyclerView. This clipping behavior is only enabled if padding is non-zero.
+ *
+ * @return true if this RecyclerView clips children to its padding and resizes (but doesn't
+ * clip) any EdgeEffect to the padded region, false otherwise.
+ *
+ * @attr name android:clipToPadding
+ */
+ @Override
+ public boolean getClipToPadding() {
+ return mClipToPadding;
+ }
+
+ /**
+ * Configure the scrolling touch slop for a specific use case.
+ *
+ * Set up the RecyclerView's scrolling motion threshold based on common usages.
+ * Valid arguments are {@link #TOUCH_SLOP_DEFAULT} and {@link #TOUCH_SLOP_PAGING}.
+ *
+ * @param slopConstant One of the <code>TOUCH_SLOP_</code> constants representing
+ * the intended usage of this RecyclerView
+ */
+ public void setScrollingTouchSlop(int slopConstant) {
+ final ViewConfiguration vc = ViewConfiguration.get(getContext());
+ switch (slopConstant) {
+ default:
+ Log.w(TAG, "setScrollingTouchSlop(): bad argument constant "
+ + slopConstant + "; using default value");
+ // fall-through
+ case TOUCH_SLOP_DEFAULT:
+ mTouchSlop = vc.getScaledTouchSlop();
+ break;
+
+ case TOUCH_SLOP_PAGING:
+ mTouchSlop = vc.getScaledPagingTouchSlop();
+ break;
+ }
+ }
+
+ /**
+ * Swaps the current adapter with the provided one. It is similar to
+ * {@link #setAdapter(Adapter)} but assumes existing adapter and the new adapter uses the same
+ * {@link ViewHolder} and does not clear the RecycledViewPool.
+ * <p>
+ * Note that it still calls onAdapterChanged callbacks.
+ *
+ * @param adapter The new adapter to set, or null to set no adapter.
+ * @param removeAndRecycleExistingViews If set to true, RecyclerView will recycle all existing
+ * Views. If adapters have stable ids and/or you want to
+ * animate the disappearing views, you may prefer to set
+ * this to false.
+ * @see #setAdapter(Adapter)
+ */
+ public void swapAdapter(Adapter adapter, boolean removeAndRecycleExistingViews) {
+ // bail out if layout is frozen
+ setLayoutFrozen(false);
+ setAdapterInternal(adapter, true, removeAndRecycleExistingViews);
+ setDataSetChangedAfterLayout();
+ requestLayout();
+ }
+ /**
+ * Set a new adapter to provide child views on demand.
+ * <p>
+ * When adapter is changed, all existing views are recycled back to the pool. If the pool has
+ * only one adapter, it will be cleared.
+ *
+ * @param adapter The new adapter to set, or null to set no adapter.
+ * @see #swapAdapter(Adapter, boolean)
+ */
+ public void setAdapter(Adapter adapter) {
+ // bail out if layout is frozen
+ setLayoutFrozen(false);
+ setAdapterInternal(adapter, false, true);
+ requestLayout();
+ }
+
+ /**
+ * Removes and recycles all views - both those currently attached, and those in the Recycler.
+ */
+ void removeAndRecycleViews() {
+ // end all running animations
+ if (mItemAnimator != null) {
+ mItemAnimator.endAnimations();
+ }
+ // Since animations are ended, mLayout.children should be equal to
+ // recyclerView.children. This may not be true if item animator's end does not work as
+ // expected. (e.g. not release children instantly). It is safer to use mLayout's child
+ // count.
+ if (mLayout != null) {
+ mLayout.removeAndRecycleAllViews(mRecycler);
+ mLayout.removeAndRecycleScrapInt(mRecycler);
+ }
+ // we should clear it here before adapters are swapped to ensure correct callbacks.
+ mRecycler.clear();
+ }
+
+ /**
+ * Replaces the current adapter with the new one and triggers listeners.
+ * @param adapter The new adapter
+ * @param compatibleWithPrevious If true, the new adapter is using the same View Holders and
+ * item types with the current adapter (helps us avoid cache
+ * invalidation).
+ * @param removeAndRecycleViews If true, we'll remove and recycle all existing views. If
+ * compatibleWithPrevious is false, this parameter is ignored.
+ */
+ private void setAdapterInternal(Adapter adapter, boolean compatibleWithPrevious,
+ boolean removeAndRecycleViews) {
+ if (mAdapter != null) {
+ mAdapter.unregisterAdapterDataObserver(mObserver);
+ mAdapter.onDetachedFromRecyclerView(this);
+ }
+ if (!compatibleWithPrevious || removeAndRecycleViews) {
+ removeAndRecycleViews();
+ }
+ mAdapterHelper.reset();
+ final Adapter oldAdapter = mAdapter;
+ mAdapter = adapter;
+ if (adapter != null) {
+ adapter.registerAdapterDataObserver(mObserver);
+ adapter.onAttachedToRecyclerView(this);
+ }
+ if (mLayout != null) {
+ mLayout.onAdapterChanged(oldAdapter, mAdapter);
+ }
+ mRecycler.onAdapterChanged(oldAdapter, mAdapter, compatibleWithPrevious);
+ mState.mStructureChanged = true;
+ markKnownViewsInvalid();
+ }
+
+ /**
+ * Retrieves the previously set adapter or null if no adapter is set.
+ *
+ * @return The previously set adapter
+ * @see #setAdapter(Adapter)
+ */
+ public Adapter getAdapter() {
+ return mAdapter;
+ }
+
+ /**
+ * Register a listener that will be notified whenever a child view is recycled.
+ *
+ * <p>This listener will be called when a LayoutManager or the RecyclerView decides
+ * that a child view is no longer needed. If an application associates expensive
+ * or heavyweight data with item views, this may be a good place to release
+ * or free those resources.</p>
+ *
+ * @param listener Listener to register, or null to clear
+ */
+ public void setRecyclerListener(RecyclerListener listener) {
+ mRecyclerListener = listener;
+ }
+
+ /**
+ * <p>Return the offset of the RecyclerView's text baseline from the its top
+ * boundary. If the LayoutManager of this RecyclerView does not support baseline alignment,
+ * this method returns -1.</p>
+ *
+ * @return the offset of the baseline within the RecyclerView's bounds or -1
+ * if baseline alignment is not supported
+ */
+ @Override
+ public int getBaseline() {
+ if (mLayout != null) {
+ return mLayout.getBaseline();
+ } else {
+ return super.getBaseline();
+ }
+ }
+
+ /**
+ * Register a listener that will be notified whenever a child view is attached to or detached
+ * from RecyclerView.
+ *
+ * <p>This listener will be called when a LayoutManager or the RecyclerView decides
+ * that a child view is no longer needed. If an application associates expensive
+ * or heavyweight data with item views, this may be a good place to release
+ * or free those resources.</p>
+ *
+ * @param listener Listener to register
+ */
+ public void addOnChildAttachStateChangeListener(OnChildAttachStateChangeListener listener) {
+ if (mOnChildAttachStateListeners == null) {
+ mOnChildAttachStateListeners = new ArrayList<>();
+ }
+ mOnChildAttachStateListeners.add(listener);
+ }
+
+ /**
+ * Removes the provided listener from child attached state listeners list.
+ *
+ * @param listener Listener to unregister
+ */
+ public void removeOnChildAttachStateChangeListener(OnChildAttachStateChangeListener listener) {
+ if (mOnChildAttachStateListeners == null) {
+ return;
+ }
+ mOnChildAttachStateListeners.remove(listener);
+ }
+
+ /**
+ * Removes all listeners that were added via
+ * {@link #addOnChildAttachStateChangeListener(OnChildAttachStateChangeListener)}.
+ */
+ public void clearOnChildAttachStateChangeListeners() {
+ if (mOnChildAttachStateListeners != null) {
+ mOnChildAttachStateListeners.clear();
+ }
+ }
+
+ /**
+ * Set the {@link LayoutManager} that this RecyclerView will use.
+ *
+ * <p>In contrast to other adapter-backed views such as {@link android.widget.ListView}
+ * or {@link android.widget.GridView}, RecyclerView allows client code to provide custom
+ * layout arrangements for child views. These arrangements are controlled by the
+ * {@link LayoutManager}. A LayoutManager must be provided for RecyclerView to function.</p>
+ *
+ * <p>Several default strategies are provided for common uses such as lists and grids.</p>
+ *
+ * @param layout LayoutManager to use
+ */
+ public void setLayoutManager(LayoutManager layout) {
+ if (layout == mLayout) {
+ return;
+ }
+ stopScroll();
+ // TODO We should do this switch a dispatchLayout pass and animate children. There is a good
+ // chance that LayoutManagers will re-use views.
+ if (mLayout != null) {
+ // end all running animations
+ if (mItemAnimator != null) {
+ mItemAnimator.endAnimations();
+ }
+ mLayout.removeAndRecycleAllViews(mRecycler);
+ mLayout.removeAndRecycleScrapInt(mRecycler);
+ mRecycler.clear();
+
+ if (mIsAttached) {
+ mLayout.dispatchDetachedFromWindow(this, mRecycler);
+ }
+ mLayout.setRecyclerView(null);
+ mLayout = null;
+ } else {
+ mRecycler.clear();
+ }
+ // this is just a defensive measure for faulty item animators.
+ mChildHelper.removeAllViewsUnfiltered();
+ mLayout = layout;
+ if (layout != null) {
+ if (layout.mRecyclerView != null) {
+ throw new IllegalArgumentException("LayoutManager " + layout
+ + " is already attached to a RecyclerView: " + layout.mRecyclerView);
+ }
+ mLayout.setRecyclerView(this);
+ if (mIsAttached) {
+ mLayout.dispatchAttachedToWindow(this);
+ }
+ }
+ mRecycler.updateViewCacheSize();
+ requestLayout();
+ }
+
+ /**
+ * Set a {@link OnFlingListener} for this {@link RecyclerView}.
+ * <p>
+ * If the {@link OnFlingListener} is set then it will receive
+ * calls to {@link #fling(int,int)} and will be able to intercept them.
+ *
+ * @param onFlingListener The {@link OnFlingListener} instance.
+ */
+ public void setOnFlingListener(@Nullable OnFlingListener onFlingListener) {
+ mOnFlingListener = onFlingListener;
+ }
+
+ /**
+ * Get the current {@link OnFlingListener} from this {@link RecyclerView}.
+ *
+ * @return The {@link OnFlingListener} instance currently set (can be null).
+ */
+ @Nullable
+ public OnFlingListener getOnFlingListener() {
+ return mOnFlingListener;
+ }
+
+ @Override
+ protected Parcelable onSaveInstanceState() {
+ SavedState state = new SavedState(super.onSaveInstanceState());
+ if (mPendingSavedState != null) {
+ state.copyFrom(mPendingSavedState);
+ } else if (mLayout != null) {
+ state.mLayoutState = mLayout.onSaveInstanceState();
+ } else {
+ state.mLayoutState = null;
+ }
+
+ return state;
+ }
+
+ @Override
+ protected void onRestoreInstanceState(Parcelable state) {
+ if (!(state instanceof SavedState)) {
+ super.onRestoreInstanceState(state);
+ return;
+ }
+
+ mPendingSavedState = (SavedState) state;
+ super.onRestoreInstanceState(mPendingSavedState.getSuperState());
+ if (mLayout != null && mPendingSavedState.mLayoutState != null) {
+ mLayout.onRestoreInstanceState(mPendingSavedState.mLayoutState);
+ }
+ }
+
+ /**
+ * Override to prevent freezing of any views created by the adapter.
+ */
+ @Override
+ protected void dispatchSaveInstanceState(SparseArray<Parcelable> container) {
+ dispatchFreezeSelfOnly(container);
+ }
+
+ /**
+ * Override to prevent thawing of any views created by the adapter.
+ */
+ @Override
+ protected void dispatchRestoreInstanceState(SparseArray<Parcelable> container) {
+ dispatchThawSelfOnly(container);
+ }
+
+ /**
+ * Adds a view to the animatingViews list.
+ * mAnimatingViews holds the child views that are currently being kept around
+ * purely for the purpose of being animated out of view. They are drawn as a regular
+ * part of the child list of the RecyclerView, but they are invisible to the LayoutManager
+ * as they are managed separately from the regular child views.
+ * @param viewHolder The ViewHolder to be removed
+ */
+ private void addAnimatingView(ViewHolder viewHolder) {
+ final View view = viewHolder.itemView;
+ final boolean alreadyParented = view.getParent() == this;
+ mRecycler.unscrapView(getChildViewHolder(view));
+ if (viewHolder.isTmpDetached()) {
+ // re-attach
+ mChildHelper.attachViewToParent(view, -1, view.getLayoutParams(), true);
+ } else if (!alreadyParented) {
+ mChildHelper.addView(view, true);
+ } else {
+ mChildHelper.hide(view);
+ }
+ }
+
+ /**
+ * Removes a view from the animatingViews list.
+ * @param view The view to be removed
+ * @see #addAnimatingView(RecyclerView.ViewHolder)
+ * @return true if an animating view is removed
+ */
+ boolean removeAnimatingView(View view) {
+ eatRequestLayout();
+ final boolean removed = mChildHelper.removeViewIfHidden(view);
+ if (removed) {
+ final ViewHolder viewHolder = getChildViewHolderInt(view);
+ mRecycler.unscrapView(viewHolder);
+ mRecycler.recycleViewHolderInternal(viewHolder);
+ if (DEBUG) {
+ Log.d(TAG, "after removing animated view: " + view + ", " + this);
+ }
+ }
+ // only clear request eaten flag if we removed the view.
+ resumeRequestLayout(!removed);
+ return removed;
+ }
+
+ /**
+ * Return the {@link LayoutManager} currently responsible for
+ * layout policy for this RecyclerView.
+ *
+ * @return The currently bound LayoutManager
+ */
+ public LayoutManager getLayoutManager() {
+ return mLayout;
+ }
+
+ /**
+ * Retrieve this RecyclerView's {@link RecycledViewPool}. This method will never return null;
+ * if no pool is set for this view a new one will be created. See
+ * {@link #setRecycledViewPool(RecycledViewPool) setRecycledViewPool} for more information.
+ *
+ * @return The pool used to store recycled item views for reuse.
+ * @see #setRecycledViewPool(RecycledViewPool)
+ */
+ public RecycledViewPool getRecycledViewPool() {
+ return mRecycler.getRecycledViewPool();
+ }
+
+ /**
+ * Recycled view pools allow multiple RecyclerViews to share a common pool of scrap views.
+ * This can be useful if you have multiple RecyclerViews with adapters that use the same
+ * view types, for example if you have several data sets with the same kinds of item views
+ * displayed by a {@link android.support.v4.view.ViewPager ViewPager}.
+ *
+ * @param pool Pool to set. If this parameter is null a new pool will be created and used.
+ */
+ public void setRecycledViewPool(RecycledViewPool pool) {
+ mRecycler.setRecycledViewPool(pool);
+ }
+
+ /**
+ * Sets a new {@link ViewCacheExtension} to be used by the Recycler.
+ *
+ * @param extension ViewCacheExtension to be used or null if you want to clear the existing one.
+ *
+ * @see {@link ViewCacheExtension#getViewForPositionAndType(Recycler, int, int)}
+ */
+ public void setViewCacheExtension(ViewCacheExtension extension) {
+ mRecycler.setViewCacheExtension(extension);
+ }
+
+ /**
+ * Set the number of offscreen views to retain before adding them to the potentially shared
+ * {@link #getRecycledViewPool() recycled view pool}.
+ *
+ * <p>The offscreen view cache stays aware of changes in the attached adapter, allowing
+ * a LayoutManager to reuse those views unmodified without needing to return to the adapter
+ * to rebind them.</p>
+ *
+ * @param size Number of views to cache offscreen before returning them to the general
+ * recycled view pool
+ */
+ public void setItemViewCacheSize(int size) {
+ mRecycler.setViewCacheSize(size);
+ }
+
+ /**
+ * Return the current scrolling state of the RecyclerView.
+ *
+ * @return {@link #SCROLL_STATE_IDLE}, {@link #SCROLL_STATE_DRAGGING} or
+ * {@link #SCROLL_STATE_SETTLING}
+ */
+ public int getScrollState() {
+ return mScrollState;
+ }
+
+ void setScrollState(int state) {
+ if (state == mScrollState) {
+ return;
+ }
+ if (DEBUG) {
+ Log.d(TAG, "setting scroll state to " + state + " from " + mScrollState,
+ new Exception());
+ }
+ mScrollState = state;
+ if (state != SCROLL_STATE_SETTLING) {
+ stopScrollersInternal();
+ }
+ dispatchOnScrollStateChanged(state);
+ }
+
+ /**
+ * Add an {@link ItemDecoration} to this RecyclerView. Item decorations can
+ * affect both measurement and drawing of individual item views.
+ *
+ * <p>Item decorations are ordered. Decorations placed earlier in the list will
+ * be run/queried/drawn first for their effects on item views. Padding added to views
+ * will be nested; a padding added by an earlier decoration will mean further
+ * item decorations in the list will be asked to draw/pad within the previous decoration's
+ * given area.</p>
+ *
+ * @param decor Decoration to add
+ * @param index Position in the decoration chain to insert this decoration at. If this value
+ * is negative the decoration will be added at the end.
+ */
+ public void addItemDecoration(ItemDecoration decor, int index) {
+ if (mLayout != null) {
+ mLayout.assertNotInLayoutOrScroll("Cannot add item decoration during a scroll or"
+ + " layout");
+ }
+ if (mItemDecorations.isEmpty()) {
+ setWillNotDraw(false);
+ }
+ if (index < 0) {
+ mItemDecorations.add(decor);
+ } else {
+ mItemDecorations.add(index, decor);
+ }
+ markItemDecorInsetsDirty();
+ requestLayout();
+ }
+
+ /**
+ * Add an {@link ItemDecoration} to this RecyclerView. Item decorations can
+ * affect both measurement and drawing of individual item views.
+ *
+ * <p>Item decorations are ordered. Decorations placed earlier in the list will
+ * be run/queried/drawn first for their effects on item views. Padding added to views
+ * will be nested; a padding added by an earlier decoration will mean further
+ * item decorations in the list will be asked to draw/pad within the previous decoration's
+ * given area.</p>
+ *
+ * @param decor Decoration to add
+ */
+ public void addItemDecoration(ItemDecoration decor) {
+ addItemDecoration(decor, -1);
+ }
+
+ /**
+ * Remove an {@link ItemDecoration} from this RecyclerView.
+ *
+ * <p>The given decoration will no longer impact the measurement and drawing of
+ * item views.</p>
+ *
+ * @param decor Decoration to remove
+ * @see #addItemDecoration(ItemDecoration)
+ */
+ public void removeItemDecoration(ItemDecoration decor) {
+ if (mLayout != null) {
+ mLayout.assertNotInLayoutOrScroll("Cannot remove item decoration during a scroll or"
+ + " layout");
+ }
+ mItemDecorations.remove(decor);
+ if (mItemDecorations.isEmpty()) {
+ setWillNotDraw(getOverScrollMode() == View.OVER_SCROLL_NEVER);
+ }
+ markItemDecorInsetsDirty();
+ requestLayout();
+ }
+
+ /**
+ * Sets the {@link ChildDrawingOrderCallback} to be used for drawing children.
+ * <p>
+ * See {@link ViewGroup#getChildDrawingOrder(int, int)} for details. Calling this method will
+ * always call {@link ViewGroup#setChildrenDrawingOrderEnabled(boolean)}. The parameter will be
+ * true if childDrawingOrderCallback is not null, false otherwise.
+ * <p>
+ * Note that child drawing order may be overridden by View's elevation.
+ *
+ * @param childDrawingOrderCallback The ChildDrawingOrderCallback to be used by the drawing
+ * system.
+ */
+ public void setChildDrawingOrderCallback(ChildDrawingOrderCallback childDrawingOrderCallback) {
+ if (childDrawingOrderCallback == mChildDrawingOrderCallback) {
+ return;
+ }
+ mChildDrawingOrderCallback = childDrawingOrderCallback;
+ setChildrenDrawingOrderEnabled(mChildDrawingOrderCallback != null);
+ }
+
+ /**
+ * Set a listener that will be notified of any changes in scroll state or position.
+ *
+ * @param listener Listener to set or null to clear
+ *
+ * @deprecated Use {@link #addOnScrollListener(OnScrollListener)} and
+ * {@link #removeOnScrollListener(OnScrollListener)}
+ */
+ @Deprecated
+ public void setOnScrollListener(OnScrollListener listener) {
+ mScrollListener = listener;
+ }
+
+ /**
+ * Add a listener that will be notified of any changes in scroll state or position.
+ *
+ * <p>Components that add a listener should take care to remove it when finished.
+ * Other components that take ownership of a view may call {@link #clearOnScrollListeners()}
+ * to remove all attached listeners.</p>
+ *
+ * @param listener listener to set or null to clear
+ */
+ public void addOnScrollListener(OnScrollListener listener) {
+ if (mScrollListeners == null) {
+ mScrollListeners = new ArrayList<>();
+ }
+ mScrollListeners.add(listener);
+ }
+
+ /**
+ * Remove a listener that was notified of any changes in scroll state or position.
+ *
+ * @param listener listener to set or null to clear
+ */
+ public void removeOnScrollListener(OnScrollListener listener) {
+ if (mScrollListeners != null) {
+ mScrollListeners.remove(listener);
+ }
+ }
+
+ /**
+ * Remove all secondary listener that were notified of any changes in scroll state or position.
+ */
+ public void clearOnScrollListeners() {
+ if (mScrollListeners != null) {
+ mScrollListeners.clear();
+ }
+ }
+
+ /**
+ * Convenience method to scroll to a certain position.
+ *
+ * RecyclerView does not implement scrolling logic, rather forwards the call to
+ * {@link com.android.internal.widget.RecyclerView.LayoutManager#scrollToPosition(int)}
+ * @param position Scroll to this adapter position
+ * @see com.android.internal.widget.RecyclerView.LayoutManager#scrollToPosition(int)
+ */
+ public void scrollToPosition(int position) {
+ if (mLayoutFrozen) {
+ return;
+ }
+ stopScroll();
+ if (mLayout == null) {
+ Log.e(TAG, "Cannot scroll to position a LayoutManager set. "
+ + "Call setLayoutManager with a non-null argument.");
+ return;
+ }
+ mLayout.scrollToPosition(position);
+ awakenScrollBars();
+ }
+
+ void jumpToPositionForSmoothScroller(int position) {
+ if (mLayout == null) {
+ return;
+ }
+ mLayout.scrollToPosition(position);
+ awakenScrollBars();
+ }
+
+ /**
+ * Starts a smooth scroll to an adapter position.
+ * <p>
+ * To support smooth scrolling, you must override
+ * {@link LayoutManager#smoothScrollToPosition(RecyclerView, State, int)} and create a
+ * {@link SmoothScroller}.
+ * <p>
+ * {@link LayoutManager} is responsible for creating the actual scroll action. If you want to
+ * provide a custom smooth scroll logic, override
+ * {@link LayoutManager#smoothScrollToPosition(RecyclerView, State, int)} in your
+ * LayoutManager.
+ *
+ * @param position The adapter position to scroll to
+ * @see LayoutManager#smoothScrollToPosition(RecyclerView, State, int)
+ */
+ public void smoothScrollToPosition(int position) {
+ if (mLayoutFrozen) {
+ return;
+ }
+ if (mLayout == null) {
+ Log.e(TAG, "Cannot smooth scroll without a LayoutManager set. "
+ + "Call setLayoutManager with a non-null argument.");
+ return;
+ }
+ mLayout.smoothScrollToPosition(this, mState, position);
+ }
+
+ @Override
+ public void scrollTo(int x, int y) {
+ Log.w(TAG, "RecyclerView does not support scrolling to an absolute position. "
+ + "Use scrollToPosition instead");
+ }
+
+ @Override
+ public void scrollBy(int x, int y) {
+ if (mLayout == null) {
+ Log.e(TAG, "Cannot scroll without a LayoutManager set. "
+ + "Call setLayoutManager with a non-null argument.");
+ return;
+ }
+ if (mLayoutFrozen) {
+ return;
+ }
+ final boolean canScrollHorizontal = mLayout.canScrollHorizontally();
+ final boolean canScrollVertical = mLayout.canScrollVertically();
+ if (canScrollHorizontal || canScrollVertical) {
+ scrollByInternal(canScrollHorizontal ? x : 0, canScrollVertical ? y : 0, null);
+ }
+ }
+
+ /**
+ * Helper method reflect data changes to the state.
+ * <p>
+ * Adapter changes during a scroll may trigger a crash because scroll assumes no data change
+ * but data actually changed.
+ * <p>
+ * This method consumes all deferred changes to avoid that case.
+ */
+ void consumePendingUpdateOperations() {
+ if (!mFirstLayoutComplete || mDataSetHasChangedAfterLayout) {
+ Trace.beginSection(TRACE_ON_DATA_SET_CHANGE_LAYOUT_TAG);
+ dispatchLayout();
+ Trace.endSection();
+ return;
+ }
+ if (!mAdapterHelper.hasPendingUpdates()) {
+ return;
+ }
+
+ // if it is only an item change (no add-remove-notifyDataSetChanged) we can check if any
+ // of the visible items is affected and if not, just ignore the change.
+ if (mAdapterHelper.hasAnyUpdateTypes(AdapterHelper.UpdateOp.UPDATE) && !mAdapterHelper
+ .hasAnyUpdateTypes(AdapterHelper.UpdateOp.ADD | AdapterHelper.UpdateOp.REMOVE
+ | AdapterHelper.UpdateOp.MOVE)) {
+ Trace.beginSection(TRACE_HANDLE_ADAPTER_UPDATES_TAG);
+ eatRequestLayout();
+ onEnterLayoutOrScroll();
+ mAdapterHelper.preProcess();
+ if (!mLayoutRequestEaten) {
+ if (hasUpdatedView()) {
+ dispatchLayout();
+ } else {
+ // no need to layout, clean state
+ mAdapterHelper.consumePostponedUpdates();
+ }
+ }
+ resumeRequestLayout(true);
+ onExitLayoutOrScroll();
+ Trace.endSection();
+ } else if (mAdapterHelper.hasPendingUpdates()) {
+ Trace.beginSection(TRACE_ON_DATA_SET_CHANGE_LAYOUT_TAG);
+ dispatchLayout();
+ Trace.endSection();
+ }
+ }
+
+ /**
+ * @return True if an existing view holder needs to be updated
+ */
+ private boolean hasUpdatedView() {
+ final int childCount = mChildHelper.getChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getChildAt(i));
+ if (holder == null || holder.shouldIgnore()) {
+ continue;
+ }
+ if (holder.isUpdated()) {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Does not perform bounds checking. Used by internal methods that have already validated input.
+ * <p>
+ * It also reports any unused scroll request to the related EdgeEffect.
+ *
+ * @param x The amount of horizontal scroll request
+ * @param y The amount of vertical scroll request
+ * @param ev The originating MotionEvent, or null if not from a touch event.
+ *
+ * @return Whether any scroll was consumed in either direction.
+ */
+ boolean scrollByInternal(int x, int y, MotionEvent ev) {
+ int unconsumedX = 0, unconsumedY = 0;
+ int consumedX = 0, consumedY = 0;
+
+ consumePendingUpdateOperations();
+ if (mAdapter != null) {
+ eatRequestLayout();
+ onEnterLayoutOrScroll();
+ Trace.beginSection(TRACE_SCROLL_TAG);
+ if (x != 0) {
+ consumedX = mLayout.scrollHorizontallyBy(x, mRecycler, mState);
+ unconsumedX = x - consumedX;
+ }
+ if (y != 0) {
+ consumedY = mLayout.scrollVerticallyBy(y, mRecycler, mState);
+ unconsumedY = y - consumedY;
+ }
+ Trace.endSection();
+ repositionShadowingViews();
+ onExitLayoutOrScroll();
+ resumeRequestLayout(false);
+ }
+ if (!mItemDecorations.isEmpty()) {
+ invalidate();
+ }
+
+ if (dispatchNestedScroll(consumedX, consumedY, unconsumedX, unconsumedY, mScrollOffset)) {
+ // Update the last touch co-ords, taking any scroll offset into account
+ mLastTouchX -= mScrollOffset[0];
+ mLastTouchY -= mScrollOffset[1];
+ if (ev != null) {
+ ev.offsetLocation(mScrollOffset[0], mScrollOffset[1]);
+ }
+ mNestedOffsets[0] += mScrollOffset[0];
+ mNestedOffsets[1] += mScrollOffset[1];
+ } else if (getOverScrollMode() != View.OVER_SCROLL_NEVER) {
+ if (ev != null) {
+ pullGlows(ev.getX(), unconsumedX, ev.getY(), unconsumedY);
+ }
+ considerReleasingGlowsOnScroll(x, y);
+ }
+ if (consumedX != 0 || consumedY != 0) {
+ dispatchOnScrolled(consumedX, consumedY);
+ }
+ if (!awakenScrollBars()) {
+ invalidate();
+ }
+ return consumedX != 0 || consumedY != 0;
+ }
+
+ /**
+ * <p>Compute the horizontal offset of the horizontal scrollbar's thumb within the horizontal
+ * range. This value is used to compute the length of the thumb within the scrollbar's track.
+ * </p>
+ *
+ * <p>The range is expressed in arbitrary units that must be the same as the units used by
+ * {@link #computeHorizontalScrollRange()} and {@link #computeHorizontalScrollExtent()}.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * <p>If you want to support scroll bars, override
+ * {@link RecyclerView.LayoutManager#computeHorizontalScrollOffset(RecyclerView.State)} in your
+ * LayoutManager. </p>
+ *
+ * @return The horizontal offset of the scrollbar's thumb
+ * @see com.android.internal.widget.RecyclerView.LayoutManager#computeHorizontalScrollOffset
+ * (RecyclerView.State)
+ */
+ @Override
+ public int computeHorizontalScrollOffset() {
+ if (mLayout == null) {
+ return 0;
+ }
+ return mLayout.canScrollHorizontally() ? mLayout.computeHorizontalScrollOffset(mState) : 0;
+ }
+
+ /**
+ * <p>Compute the horizontal extent of the horizontal scrollbar's thumb within the
+ * horizontal range. This value is used to compute the length of the thumb within the
+ * scrollbar's track.</p>
+ *
+ * <p>The range is expressed in arbitrary units that must be the same as the units used by
+ * {@link #computeHorizontalScrollRange()} and {@link #computeHorizontalScrollOffset()}.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * <p>If you want to support scroll bars, override
+ * {@link RecyclerView.LayoutManager#computeHorizontalScrollExtent(RecyclerView.State)} in your
+ * LayoutManager.</p>
+ *
+ * @return The horizontal extent of the scrollbar's thumb
+ * @see RecyclerView.LayoutManager#computeHorizontalScrollExtent(RecyclerView.State)
+ */
+ @Override
+ public int computeHorizontalScrollExtent() {
+ if (mLayout == null) {
+ return 0;
+ }
+ return mLayout.canScrollHorizontally() ? mLayout.computeHorizontalScrollExtent(mState) : 0;
+ }
+
+ /**
+ * <p>Compute the horizontal range that the horizontal scrollbar represents.</p>
+ *
+ * <p>The range is expressed in arbitrary units that must be the same as the units used by
+ * {@link #computeHorizontalScrollExtent()} and {@link #computeHorizontalScrollOffset()}.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * <p>If you want to support scroll bars, override
+ * {@link RecyclerView.LayoutManager#computeHorizontalScrollRange(RecyclerView.State)} in your
+ * LayoutManager.</p>
+ *
+ * @return The total horizontal range represented by the vertical scrollbar
+ * @see RecyclerView.LayoutManager#computeHorizontalScrollRange(RecyclerView.State)
+ */
+ @Override
+ public int computeHorizontalScrollRange() {
+ if (mLayout == null) {
+ return 0;
+ }
+ return mLayout.canScrollHorizontally() ? mLayout.computeHorizontalScrollRange(mState) : 0;
+ }
+
+ /**
+ * <p>Compute the vertical offset of the vertical scrollbar's thumb within the vertical range.
+ * This value is used to compute the length of the thumb within the scrollbar's track. </p>
+ *
+ * <p>The range is expressed in arbitrary units that must be the same as the units used by
+ * {@link #computeVerticalScrollRange()} and {@link #computeVerticalScrollExtent()}.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * <p>If you want to support scroll bars, override
+ * {@link RecyclerView.LayoutManager#computeVerticalScrollOffset(RecyclerView.State)} in your
+ * LayoutManager.</p>
+ *
+ * @return The vertical offset of the scrollbar's thumb
+ * @see com.android.internal.widget.RecyclerView.LayoutManager#computeVerticalScrollOffset
+ * (RecyclerView.State)
+ */
+ @Override
+ public int computeVerticalScrollOffset() {
+ if (mLayout == null) {
+ return 0;
+ }
+ return mLayout.canScrollVertically() ? mLayout.computeVerticalScrollOffset(mState) : 0;
+ }
+
+ /**
+ * <p>Compute the vertical extent of the vertical scrollbar's thumb within the vertical range.
+ * This value is used to compute the length of the thumb within the scrollbar's track.</p>
+ *
+ * <p>The range is expressed in arbitrary units that must be the same as the units used by
+ * {@link #computeVerticalScrollRange()} and {@link #computeVerticalScrollOffset()}.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * <p>If you want to support scroll bars, override
+ * {@link RecyclerView.LayoutManager#computeVerticalScrollExtent(RecyclerView.State)} in your
+ * LayoutManager.</p>
+ *
+ * @return The vertical extent of the scrollbar's thumb
+ * @see RecyclerView.LayoutManager#computeVerticalScrollExtent(RecyclerView.State)
+ */
+ @Override
+ public int computeVerticalScrollExtent() {
+ if (mLayout == null) {
+ return 0;
+ }
+ return mLayout.canScrollVertically() ? mLayout.computeVerticalScrollExtent(mState) : 0;
+ }
+
+ /**
+ * <p>Compute the vertical range that the vertical scrollbar represents.</p>
+ *
+ * <p>The range is expressed in arbitrary units that must be the same as the units used by
+ * {@link #computeVerticalScrollExtent()} and {@link #computeVerticalScrollOffset()}.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * <p>If you want to support scroll bars, override
+ * {@link RecyclerView.LayoutManager#computeVerticalScrollRange(RecyclerView.State)} in your
+ * LayoutManager.</p>
+ *
+ * @return The total vertical range represented by the vertical scrollbar
+ * @see RecyclerView.LayoutManager#computeVerticalScrollRange(RecyclerView.State)
+ */
+ @Override
+ public int computeVerticalScrollRange() {
+ if (mLayout == null) {
+ return 0;
+ }
+ return mLayout.canScrollVertically() ? mLayout.computeVerticalScrollRange(mState) : 0;
+ }
+
+
+ void eatRequestLayout() {
+ mEatRequestLayout++;
+ if (mEatRequestLayout == 1 && !mLayoutFrozen) {
+ mLayoutRequestEaten = false;
+ }
+ }
+
+ void resumeRequestLayout(boolean performLayoutChildren) {
+ if (mEatRequestLayout < 1) {
+ //noinspection PointlessBooleanExpression
+ if (DEBUG) {
+ throw new IllegalStateException("invalid eat request layout count");
+ }
+ mEatRequestLayout = 1;
+ }
+ if (!performLayoutChildren) {
+ // Reset the layout request eaten counter.
+ // This is necessary since eatRequest calls can be nested in which case the other
+ // call will override the inner one.
+ // for instance:
+ // eat layout for process adapter updates
+ // eat layout for dispatchLayout
+ // a bunch of req layout calls arrive
+
+ mLayoutRequestEaten = false;
+ }
+ if (mEatRequestLayout == 1) {
+ // when layout is frozen we should delay dispatchLayout()
+ if (performLayoutChildren && mLayoutRequestEaten && !mLayoutFrozen
+ && mLayout != null && mAdapter != null) {
+ dispatchLayout();
+ }
+ if (!mLayoutFrozen) {
+ mLayoutRequestEaten = false;
+ }
+ }
+ mEatRequestLayout--;
+ }
+
+ /**
+ * Enable or disable layout and scroll. After <code>setLayoutFrozen(true)</code> is called,
+ * Layout requests will be postponed until <code>setLayoutFrozen(false)</code> is called;
+ * child views are not updated when RecyclerView is frozen, {@link #smoothScrollBy(int, int)},
+ * {@link #scrollBy(int, int)}, {@link #scrollToPosition(int)} and
+ * {@link #smoothScrollToPosition(int)} are dropped; TouchEvents and GenericMotionEvents are
+ * dropped; {@link LayoutManager#onFocusSearchFailed(View, int, Recycler, State)} will not be
+ * called.
+ *
+ * <p>
+ * <code>setLayoutFrozen(true)</code> does not prevent app from directly calling {@link
+ * LayoutManager#scrollToPosition(int)}, {@link LayoutManager#smoothScrollToPosition(
+ * RecyclerView, State, int)}.
+ * <p>
+ * {@link #setAdapter(Adapter)} and {@link #swapAdapter(Adapter, boolean)} will automatically
+ * stop frozen.
+ * <p>
+ * Note: Running ItemAnimator is not stopped automatically, it's caller's
+ * responsibility to call ItemAnimator.end().
+ *
+ * @param frozen true to freeze layout and scroll, false to re-enable.
+ */
+ public void setLayoutFrozen(boolean frozen) {
+ if (frozen != mLayoutFrozen) {
+ assertNotInLayoutOrScroll("Do not setLayoutFrozen in layout or scroll");
+ if (!frozen) {
+ mLayoutFrozen = false;
+ if (mLayoutRequestEaten && mLayout != null && mAdapter != null) {
+ requestLayout();
+ }
+ mLayoutRequestEaten = false;
+ } else {
+ final long now = SystemClock.uptimeMillis();
+ MotionEvent cancelEvent = MotionEvent.obtain(now, now,
+ MotionEvent.ACTION_CANCEL, 0.0f, 0.0f, 0);
+ onTouchEvent(cancelEvent);
+ mLayoutFrozen = true;
+ mIgnoreMotionEventTillDown = true;
+ stopScroll();
+ }
+ }
+ }
+
+ /**
+ * Returns true if layout and scroll are frozen.
+ *
+ * @return true if layout and scroll are frozen
+ * @see #setLayoutFrozen(boolean)
+ */
+ public boolean isLayoutFrozen() {
+ return mLayoutFrozen;
+ }
+
+ /**
+ * Animate a scroll by the given amount of pixels along either axis.
+ *
+ * @param dx Pixels to scroll horizontally
+ * @param dy Pixels to scroll vertically
+ */
+ public void smoothScrollBy(int dx, int dy) {
+ smoothScrollBy(dx, dy, null);
+ }
+
+ /**
+ * Animate a scroll by the given amount of pixels along either axis.
+ *
+ * @param dx Pixels to scroll horizontally
+ * @param dy Pixels to scroll vertically
+ * @param interpolator {@link Interpolator} to be used for scrolling. If it is
+ * {@code null}, RecyclerView is going to use the default interpolator.
+ */
+ public void smoothScrollBy(int dx, int dy, Interpolator interpolator) {
+ if (mLayout == null) {
+ Log.e(TAG, "Cannot smooth scroll without a LayoutManager set. "
+ + "Call setLayoutManager with a non-null argument.");
+ return;
+ }
+ if (mLayoutFrozen) {
+ return;
+ }
+ if (!mLayout.canScrollHorizontally()) {
+ dx = 0;
+ }
+ if (!mLayout.canScrollVertically()) {
+ dy = 0;
+ }
+ if (dx != 0 || dy != 0) {
+ mViewFlinger.smoothScrollBy(dx, dy, interpolator);
+ }
+ }
+
+ /**
+ * Begin a standard fling with an initial velocity along each axis in pixels per second.
+ * If the velocity given is below the system-defined minimum this method will return false
+ * and no fling will occur.
+ *
+ * @param velocityX Initial horizontal velocity in pixels per second
+ * @param velocityY Initial vertical velocity in pixels per second
+ * @return true if the fling was started, false if the velocity was too low to fling or
+ * LayoutManager does not support scrolling in the axis fling is issued.
+ *
+ * @see LayoutManager#canScrollVertically()
+ * @see LayoutManager#canScrollHorizontally()
+ */
+ public boolean fling(int velocityX, int velocityY) {
+ if (mLayout == null) {
+ Log.e(TAG, "Cannot fling without a LayoutManager set. "
+ + "Call setLayoutManager with a non-null argument.");
+ return false;
+ }
+ if (mLayoutFrozen) {
+ return false;
+ }
+
+ final boolean canScrollHorizontal = mLayout.canScrollHorizontally();
+ final boolean canScrollVertical = mLayout.canScrollVertically();
+
+ if (!canScrollHorizontal || Math.abs(velocityX) < mMinFlingVelocity) {
+ velocityX = 0;
+ }
+ if (!canScrollVertical || Math.abs(velocityY) < mMinFlingVelocity) {
+ velocityY = 0;
+ }
+ if (velocityX == 0 && velocityY == 0) {
+ // If we don't have any velocity, return false
+ return false;
+ }
+
+ if (!dispatchNestedPreFling(velocityX, velocityY)) {
+ final boolean canScroll = canScrollHorizontal || canScrollVertical;
+ dispatchNestedFling(velocityX, velocityY, canScroll);
+
+ if (mOnFlingListener != null && mOnFlingListener.onFling(velocityX, velocityY)) {
+ return true;
+ }
+
+ if (canScroll) {
+ velocityX = Math.max(-mMaxFlingVelocity, Math.min(velocityX, mMaxFlingVelocity));
+ velocityY = Math.max(-mMaxFlingVelocity, Math.min(velocityY, mMaxFlingVelocity));
+ mViewFlinger.fling(velocityX, velocityY);
+ return true;
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Stop any current scroll in progress, such as one started by
+ * {@link #smoothScrollBy(int, int)}, {@link #fling(int, int)} or a touch-initiated fling.
+ */
+ public void stopScroll() {
+ setScrollState(SCROLL_STATE_IDLE);
+ stopScrollersInternal();
+ }
+
+ /**
+ * Similar to {@link #stopScroll()} but does not set the state.
+ */
+ private void stopScrollersInternal() {
+ mViewFlinger.stop();
+ if (mLayout != null) {
+ mLayout.stopSmoothScroller();
+ }
+ }
+
+ /**
+ * Returns the minimum velocity to start a fling.
+ *
+ * @return The minimum velocity to start a fling
+ */
+ public int getMinFlingVelocity() {
+ return mMinFlingVelocity;
+ }
+
+
+ /**
+ * Returns the maximum fling velocity used by this RecyclerView.
+ *
+ * @return The maximum fling velocity used by this RecyclerView.
+ */
+ public int getMaxFlingVelocity() {
+ return mMaxFlingVelocity;
+ }
+
+ /**
+ * Apply a pull to relevant overscroll glow effects
+ */
+ private void pullGlows(float x, float overscrollX, float y, float overscrollY) {
+ boolean invalidate = false;
+ if (overscrollX < 0) {
+ ensureLeftGlow();
+ mLeftGlow.onPull(-overscrollX / getWidth(), 1f - y / getHeight());
+ invalidate = true;
+ } else if (overscrollX > 0) {
+ ensureRightGlow();
+ mRightGlow.onPull(overscrollX / getWidth(), y / getHeight());
+ invalidate = true;
+ }
+
+ if (overscrollY < 0) {
+ ensureTopGlow();
+ mTopGlow.onPull(-overscrollY / getHeight(), x / getWidth());
+ invalidate = true;
+ } else if (overscrollY > 0) {
+ ensureBottomGlow();
+ mBottomGlow.onPull(overscrollY / getHeight(), 1f - x / getWidth());
+ invalidate = true;
+ }
+
+ if (invalidate || overscrollX != 0 || overscrollY != 0) {
+ postInvalidateOnAnimation();
+ }
+ }
+
+ private void releaseGlows() {
+ boolean needsInvalidate = false;
+ if (mLeftGlow != null) {
+ mLeftGlow.onRelease();
+ needsInvalidate = true;
+ }
+ if (mTopGlow != null) {
+ mTopGlow.onRelease();
+ needsInvalidate = true;
+ }
+ if (mRightGlow != null) {
+ mRightGlow.onRelease();
+ needsInvalidate = true;
+ }
+ if (mBottomGlow != null) {
+ mBottomGlow.onRelease();
+ needsInvalidate = true;
+ }
+ if (needsInvalidate) {
+ postInvalidateOnAnimation();
+ }
+ }
+
+ void considerReleasingGlowsOnScroll(int dx, int dy) {
+ boolean needsInvalidate = false;
+ if (mLeftGlow != null && !mLeftGlow.isFinished() && dx > 0) {
+ mLeftGlow.onRelease();
+ needsInvalidate = true;
+ }
+ if (mRightGlow != null && !mRightGlow.isFinished() && dx < 0) {
+ mRightGlow.onRelease();
+ needsInvalidate = true;
+ }
+ if (mTopGlow != null && !mTopGlow.isFinished() && dy > 0) {
+ mTopGlow.onRelease();
+ needsInvalidate = true;
+ }
+ if (mBottomGlow != null && !mBottomGlow.isFinished() && dy < 0) {
+ mBottomGlow.onRelease();
+ needsInvalidate = true;
+ }
+ if (needsInvalidate) {
+ postInvalidateOnAnimation();
+ }
+ }
+
+ void absorbGlows(int velocityX, int velocityY) {
+ if (velocityX < 0) {
+ ensureLeftGlow();
+ mLeftGlow.onAbsorb(-velocityX);
+ } else if (velocityX > 0) {
+ ensureRightGlow();
+ mRightGlow.onAbsorb(velocityX);
+ }
+
+ if (velocityY < 0) {
+ ensureTopGlow();
+ mTopGlow.onAbsorb(-velocityY);
+ } else if (velocityY > 0) {
+ ensureBottomGlow();
+ mBottomGlow.onAbsorb(velocityY);
+ }
+
+ if (velocityX != 0 || velocityY != 0) {
+ postInvalidateOnAnimation();
+ }
+ }
+
+ void ensureLeftGlow() {
+ if (mLeftGlow != null) {
+ return;
+ }
+ mLeftGlow = new EdgeEffect(getContext());
+ if (mClipToPadding) {
+ mLeftGlow.setSize(getMeasuredHeight() - getPaddingTop() - getPaddingBottom(),
+ getMeasuredWidth() - getPaddingLeft() - getPaddingRight());
+ } else {
+ mLeftGlow.setSize(getMeasuredHeight(), getMeasuredWidth());
+ }
+ }
+
+ void ensureRightGlow() {
+ if (mRightGlow != null) {
+ return;
+ }
+ mRightGlow = new EdgeEffect(getContext());
+ if (mClipToPadding) {
+ mRightGlow.setSize(getMeasuredHeight() - getPaddingTop() - getPaddingBottom(),
+ getMeasuredWidth() - getPaddingLeft() - getPaddingRight());
+ } else {
+ mRightGlow.setSize(getMeasuredHeight(), getMeasuredWidth());
+ }
+ }
+
+ void ensureTopGlow() {
+ if (mTopGlow != null) {
+ return;
+ }
+ mTopGlow = new EdgeEffect(getContext());
+ if (mClipToPadding) {
+ mTopGlow.setSize(getMeasuredWidth() - getPaddingLeft() - getPaddingRight(),
+ getMeasuredHeight() - getPaddingTop() - getPaddingBottom());
+ } else {
+ mTopGlow.setSize(getMeasuredWidth(), getMeasuredHeight());
+ }
+
+ }
+
+ void ensureBottomGlow() {
+ if (mBottomGlow != null) {
+ return;
+ }
+ mBottomGlow = new EdgeEffect(getContext());
+ if (mClipToPadding) {
+ mBottomGlow.setSize(getMeasuredWidth() - getPaddingLeft() - getPaddingRight(),
+ getMeasuredHeight() - getPaddingTop() - getPaddingBottom());
+ } else {
+ mBottomGlow.setSize(getMeasuredWidth(), getMeasuredHeight());
+ }
+ }
+
+ void invalidateGlows() {
+ mLeftGlow = mRightGlow = mTopGlow = mBottomGlow = null;
+ }
+
+ /**
+ * Since RecyclerView is a collection ViewGroup that includes virtual children (items that are
+ * in the Adapter but not visible in the UI), it employs a more involved focus search strategy
+ * that differs from other ViewGroups.
+ * <p>
+ * It first does a focus search within the RecyclerView. If this search finds a View that is in
+ * the focus direction with respect to the currently focused View, RecyclerView returns that
+ * child as the next focus target. When it cannot find such child, it calls
+ * {@link LayoutManager#onFocusSearchFailed(View, int, Recycler, State)} to layout more Views
+ * in the focus search direction. If LayoutManager adds a View that matches the
+ * focus search criteria, it will be returned as the focus search result. Otherwise,
+ * RecyclerView will call parent to handle the focus search like a regular ViewGroup.
+ * <p>
+ * When the direction is {@link View#FOCUS_FORWARD} or {@link View#FOCUS_BACKWARD}, a View that
+ * is not in the focus direction is still valid focus target which may not be the desired
+ * behavior if the Adapter has more children in the focus direction. To handle this case,
+ * RecyclerView converts the focus direction to an absolute direction and makes a preliminary
+ * focus search in that direction. If there are no Views to gain focus, it will call
+ * {@link LayoutManager#onFocusSearchFailed(View, int, Recycler, State)} before running a
+ * focus search with the original (relative) direction. This allows RecyclerView to provide
+ * better candidates to the focus search while still allowing the view system to take focus from
+ * the RecyclerView and give it to a more suitable child if such child exists.
+ *
+ * @param focused The view that currently has focus
+ * @param direction One of {@link View#FOCUS_UP}, {@link View#FOCUS_DOWN},
+ * {@link View#FOCUS_LEFT}, {@link View#FOCUS_RIGHT}, {@link View#FOCUS_FORWARD},
+ * {@link View#FOCUS_BACKWARD} or 0 for not applicable.
+ *
+ * @return A new View that can be the next focus after the focused View
+ */
+ @Override
+ public View focusSearch(View focused, int direction) {
+ View result = mLayout.onInterceptFocusSearch(focused, direction);
+ if (result != null) {
+ return result;
+ }
+ final boolean canRunFocusFailure = mAdapter != null && mLayout != null
+ && !isComputingLayout() && !mLayoutFrozen;
+
+ final FocusFinder ff = FocusFinder.getInstance();
+ if (canRunFocusFailure
+ && (direction == View.FOCUS_FORWARD || direction == View.FOCUS_BACKWARD)) {
+ // convert direction to absolute direction and see if we have a view there and if not
+ // tell LayoutManager to add if it can.
+ boolean needsFocusFailureLayout = false;
+ if (mLayout.canScrollVertically()) {
+ final int absDir =
+ direction == View.FOCUS_FORWARD ? View.FOCUS_DOWN : View.FOCUS_UP;
+ final View found = ff.findNextFocus(this, focused, absDir);
+ needsFocusFailureLayout = found == null;
+ if (FORCE_ABS_FOCUS_SEARCH_DIRECTION) {
+ // Workaround for broken FOCUS_BACKWARD in API 15 and older devices.
+ direction = absDir;
+ }
+ }
+ if (!needsFocusFailureLayout && mLayout.canScrollHorizontally()) {
+ boolean rtl = mLayout.getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
+ final int absDir = (direction == View.FOCUS_FORWARD) ^ rtl
+ ? View.FOCUS_RIGHT : View.FOCUS_LEFT;
+ final View found = ff.findNextFocus(this, focused, absDir);
+ needsFocusFailureLayout = found == null;
+ if (FORCE_ABS_FOCUS_SEARCH_DIRECTION) {
+ // Workaround for broken FOCUS_BACKWARD in API 15 and older devices.
+ direction = absDir;
+ }
+ }
+ if (needsFocusFailureLayout) {
+ consumePendingUpdateOperations();
+ final View focusedItemView = findContainingItemView(focused);
+ if (focusedItemView == null) {
+ // panic, focused view is not a child anymore, cannot call super.
+ return null;
+ }
+ eatRequestLayout();
+ mLayout.onFocusSearchFailed(focused, direction, mRecycler, mState);
+ resumeRequestLayout(false);
+ }
+ result = ff.findNextFocus(this, focused, direction);
+ } else {
+ result = ff.findNextFocus(this, focused, direction);
+ if (result == null && canRunFocusFailure) {
+ consumePendingUpdateOperations();
+ final View focusedItemView = findContainingItemView(focused);
+ if (focusedItemView == null) {
+ // panic, focused view is not a child anymore, cannot call super.
+ return null;
+ }
+ eatRequestLayout();
+ result = mLayout.onFocusSearchFailed(focused, direction, mRecycler, mState);
+ resumeRequestLayout(false);
+ }
+ }
+ return isPreferredNextFocus(focused, result, direction)
+ ? result : super.focusSearch(focused, direction);
+ }
+
+ /**
+ * Checks if the new focus candidate is a good enough candidate such that RecyclerView will
+ * assign it as the next focus View instead of letting view hierarchy decide.
+ * A good candidate means a View that is aligned in the focus direction wrt the focused View
+ * and is not the RecyclerView itself.
+ * When this method returns false, RecyclerView will let the parent make the decision so the
+ * same View may still get the focus as a result of that search.
+ */
+ private boolean isPreferredNextFocus(View focused, View next, int direction) {
+ if (next == null || next == this) {
+ return false;
+ }
+ if (focused == null) {
+ return true;
+ }
+
+ if (direction == View.FOCUS_FORWARD || direction == View.FOCUS_BACKWARD) {
+ final boolean rtl = mLayout.getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
+ final int absHorizontal = (direction == View.FOCUS_FORWARD) ^ rtl
+ ? View.FOCUS_RIGHT : View.FOCUS_LEFT;
+ if (isPreferredNextFocusAbsolute(focused, next, absHorizontal)) {
+ return true;
+ }
+ if (direction == View.FOCUS_FORWARD) {
+ return isPreferredNextFocusAbsolute(focused, next, View.FOCUS_DOWN);
+ } else {
+ return isPreferredNextFocusAbsolute(focused, next, View.FOCUS_UP);
+ }
+ } else {
+ return isPreferredNextFocusAbsolute(focused, next, direction);
+ }
+
+ }
+
+ /**
+ * Logic taken from FocusSearch#isCandidate
+ */
+ private boolean isPreferredNextFocusAbsolute(View focused, View next, int direction) {
+ mTempRect.set(0, 0, focused.getWidth(), focused.getHeight());
+ mTempRect2.set(0, 0, next.getWidth(), next.getHeight());
+ offsetDescendantRectToMyCoords(focused, mTempRect);
+ offsetDescendantRectToMyCoords(next, mTempRect2);
+ switch (direction) {
+ case View.FOCUS_LEFT:
+ return (mTempRect.right > mTempRect2.right
+ || mTempRect.left >= mTempRect2.right)
+ && mTempRect.left > mTempRect2.left;
+ case View.FOCUS_RIGHT:
+ return (mTempRect.left < mTempRect2.left
+ || mTempRect.right <= mTempRect2.left)
+ && mTempRect.right < mTempRect2.right;
+ case View.FOCUS_UP:
+ return (mTempRect.bottom > mTempRect2.bottom
+ || mTempRect.top >= mTempRect2.bottom)
+ && mTempRect.top > mTempRect2.top;
+ case View.FOCUS_DOWN:
+ return (mTempRect.top < mTempRect2.top
+ || mTempRect.bottom <= mTempRect2.top)
+ && mTempRect.bottom < mTempRect2.bottom;
+ }
+ throw new IllegalArgumentException("direction must be absolute. received:" + direction);
+ }
+
+ @Override
+ public void requestChildFocus(View child, View focused) {
+ if (!mLayout.onRequestChildFocus(this, mState, child, focused) && focused != null) {
+ mTempRect.set(0, 0, focused.getWidth(), focused.getHeight());
+
+ // get item decor offsets w/o refreshing. If they are invalid, there will be another
+ // layout pass to fix them, then it is LayoutManager's responsibility to keep focused
+ // View in viewport.
+ final ViewGroup.LayoutParams focusedLayoutParams = focused.getLayoutParams();
+ if (focusedLayoutParams instanceof LayoutParams) {
+ // if focused child has item decors, use them. Otherwise, ignore.
+ final LayoutParams lp = (LayoutParams) focusedLayoutParams;
+ if (!lp.mInsetsDirty) {
+ final Rect insets = lp.mDecorInsets;
+ mTempRect.left -= insets.left;
+ mTempRect.right += insets.right;
+ mTempRect.top -= insets.top;
+ mTempRect.bottom += insets.bottom;
+ }
+ }
+
+ offsetDescendantRectToMyCoords(focused, mTempRect);
+ offsetRectIntoDescendantCoords(child, mTempRect);
+ requestChildRectangleOnScreen(child, mTempRect, !mFirstLayoutComplete);
+ }
+ super.requestChildFocus(child, focused);
+ }
+
+ @Override
+ public boolean requestChildRectangleOnScreen(View child, Rect rect, boolean immediate) {
+ return mLayout.requestChildRectangleOnScreen(this, child, rect, immediate);
+ }
+
+ @Override
+ public void addFocusables(ArrayList<View> views, int direction, int focusableMode) {
+ if (mLayout == null || !mLayout.onAddFocusables(this, views, direction, focusableMode)) {
+ super.addFocusables(views, direction, focusableMode);
+ }
+ }
+
+ @Override
+ protected boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect) {
+ if (isComputingLayout()) {
+ // if we are in the middle of a layout calculation, don't let any child take focus.
+ // RV will handle it after layout calculation is finished.
+ return false;
+ }
+ return super.onRequestFocusInDescendants(direction, previouslyFocusedRect);
+ }
+
+ @Override
+ protected void onAttachedToWindow() {
+ super.onAttachedToWindow();
+ mLayoutOrScrollCounter = 0;
+ mIsAttached = true;
+ mFirstLayoutComplete = mFirstLayoutComplete && !isLayoutRequested();
+ if (mLayout != null) {
+ mLayout.dispatchAttachedToWindow(this);
+ }
+ mPostedAnimatorRunner = false;
+
+ if (ALLOW_THREAD_GAP_WORK) {
+ // Register with gap worker
+ mGapWorker = GapWorker.sGapWorker.get();
+ if (mGapWorker == null) {
+ mGapWorker = new GapWorker();
+
+ // break 60 fps assumption if data from display appears valid
+ // NOTE: we only do this query once, statically, because it's very expensive (> 1ms)
+ Display display = getDisplay();
+ float refreshRate = 60.0f;
+ if (!isInEditMode() && display != null) {
+ float displayRefreshRate = display.getRefreshRate();
+ if (displayRefreshRate >= 30.0f) {
+ refreshRate = displayRefreshRate;
+ }
+ }
+ mGapWorker.mFrameIntervalNs = (long) (1000000000 / refreshRate);
+ GapWorker.sGapWorker.set(mGapWorker);
+ }
+ mGapWorker.add(this);
+ }
+ }
+
+ @Override
+ protected void onDetachedFromWindow() {
+ super.onDetachedFromWindow();
+ if (mItemAnimator != null) {
+ mItemAnimator.endAnimations();
+ }
+ stopScroll();
+ mIsAttached = false;
+ if (mLayout != null) {
+ mLayout.dispatchDetachedFromWindow(this, mRecycler);
+ }
+ mPendingAccessibilityImportanceChange.clear();
+ removeCallbacks(mItemAnimatorRunner);
+ mViewInfoStore.onDetach();
+
+ if (ALLOW_THREAD_GAP_WORK) {
+ // Unregister with gap worker
+ mGapWorker.remove(this);
+ mGapWorker = null;
+ }
+ }
+
+ /**
+ * Returns true if RecyclerView is attached to window.
+ */
+ // @override
+ public boolean isAttachedToWindow() {
+ return mIsAttached;
+ }
+
+ /**
+ * Checks if RecyclerView is in the middle of a layout or scroll and throws an
+ * {@link IllegalStateException} if it <b>is not</b>.
+ *
+ * @param message The message for the exception. Can be null.
+ * @see #assertNotInLayoutOrScroll(String)
+ */
+ void assertInLayoutOrScroll(String message) {
+ if (!isComputingLayout()) {
+ if (message == null) {
+ throw new IllegalStateException("Cannot call this method unless RecyclerView is "
+ + "computing a layout or scrolling");
+ }
+ throw new IllegalStateException(message);
+
+ }
+ }
+
+ /**
+ * Checks if RecyclerView is in the middle of a layout or scroll and throws an
+ * {@link IllegalStateException} if it <b>is</b>.
+ *
+ * @param message The message for the exception. Can be null.
+ * @see #assertInLayoutOrScroll(String)
+ */
+ void assertNotInLayoutOrScroll(String message) {
+ if (isComputingLayout()) {
+ if (message == null) {
+ throw new IllegalStateException("Cannot call this method while RecyclerView is "
+ + "computing a layout or scrolling");
+ }
+ throw new IllegalStateException(message);
+ }
+ if (mDispatchScrollCounter > 0) {
+ Log.w(TAG, "Cannot call this method in a scroll callback. Scroll callbacks might be run"
+ + " during a measure & layout pass where you cannot change the RecyclerView"
+ + " data. Any method call that might change the structure of the RecyclerView"
+ + " or the adapter contents should be postponed to the next frame.",
+ new IllegalStateException(""));
+ }
+ }
+
+ /**
+ * Add an {@link OnItemTouchListener} to intercept touch events before they are dispatched
+ * to child views or this view's standard scrolling behavior.
+ *
+ * <p>Client code may use listeners to implement item manipulation behavior. Once a listener
+ * returns true from
+ * {@link OnItemTouchListener#onInterceptTouchEvent(RecyclerView, MotionEvent)} its
+ * {@link OnItemTouchListener#onTouchEvent(RecyclerView, MotionEvent)} method will be called
+ * for each incoming MotionEvent until the end of the gesture.</p>
+ *
+ * @param listener Listener to add
+ * @see SimpleOnItemTouchListener
+ */
+ public void addOnItemTouchListener(OnItemTouchListener listener) {
+ mOnItemTouchListeners.add(listener);
+ }
+
+ /**
+ * Remove an {@link OnItemTouchListener}. It will no longer be able to intercept touch events.
+ *
+ * @param listener Listener to remove
+ */
+ public void removeOnItemTouchListener(OnItemTouchListener listener) {
+ mOnItemTouchListeners.remove(listener);
+ if (mActiveOnItemTouchListener == listener) {
+ mActiveOnItemTouchListener = null;
+ }
+ }
+
+ private boolean dispatchOnItemTouchIntercept(MotionEvent e) {
+ final int action = e.getAction();
+ if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_DOWN) {
+ mActiveOnItemTouchListener = null;
+ }
+
+ final int listenerCount = mOnItemTouchListeners.size();
+ for (int i = 0; i < listenerCount; i++) {
+ final OnItemTouchListener listener = mOnItemTouchListeners.get(i);
+ if (listener.onInterceptTouchEvent(this, e) && action != MotionEvent.ACTION_CANCEL) {
+ mActiveOnItemTouchListener = listener;
+ return true;
+ }
+ }
+ return false;
+ }
+
+ private boolean dispatchOnItemTouch(MotionEvent e) {
+ final int action = e.getAction();
+ if (mActiveOnItemTouchListener != null) {
+ if (action == MotionEvent.ACTION_DOWN) {
+ // Stale state from a previous gesture, we're starting a new one. Clear it.
+ mActiveOnItemTouchListener = null;
+ } else {
+ mActiveOnItemTouchListener.onTouchEvent(this, e);
+ if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
+ // Clean up for the next gesture.
+ mActiveOnItemTouchListener = null;
+ }
+ return true;
+ }
+ }
+
+ // Listeners will have already received the ACTION_DOWN via dispatchOnItemTouchIntercept
+ // as called from onInterceptTouchEvent; skip it.
+ if (action != MotionEvent.ACTION_DOWN) {
+ final int listenerCount = mOnItemTouchListeners.size();
+ for (int i = 0; i < listenerCount; i++) {
+ final OnItemTouchListener listener = mOnItemTouchListeners.get(i);
+ if (listener.onInterceptTouchEvent(this, e)) {
+ mActiveOnItemTouchListener = listener;
+ return true;
+ }
+ }
+ }
+ return false;
+ }
+
+ @Override
+ public boolean onInterceptTouchEvent(MotionEvent e) {
+ if (mLayoutFrozen) {
+ // When layout is frozen, RV does not intercept the motion event.
+ // A child view e.g. a button may still get the click.
+ return false;
+ }
+ if (dispatchOnItemTouchIntercept(e)) {
+ cancelTouch();
+ return true;
+ }
+
+ if (mLayout == null) {
+ return false;
+ }
+
+ final boolean canScrollHorizontally = mLayout.canScrollHorizontally();
+ final boolean canScrollVertically = mLayout.canScrollVertically();
+
+ if (mVelocityTracker == null) {
+ mVelocityTracker = VelocityTracker.obtain();
+ }
+ mVelocityTracker.addMovement(e);
+
+ final int action = e.getActionMasked();
+ final int actionIndex = e.getActionIndex();
+
+ switch (action) {
+ case MotionEvent.ACTION_DOWN:
+ if (mIgnoreMotionEventTillDown) {
+ mIgnoreMotionEventTillDown = false;
+ }
+ mScrollPointerId = e.getPointerId(0);
+ mInitialTouchX = mLastTouchX = (int) (e.getX() + 0.5f);
+ mInitialTouchY = mLastTouchY = (int) (e.getY() + 0.5f);
+
+ if (mScrollState == SCROLL_STATE_SETTLING) {
+ getParent().requestDisallowInterceptTouchEvent(true);
+ setScrollState(SCROLL_STATE_DRAGGING);
+ }
+
+ // Clear the nested offsets
+ mNestedOffsets[0] = mNestedOffsets[1] = 0;
+
+ int nestedScrollAxis = View.SCROLL_AXIS_NONE;
+ if (canScrollHorizontally) {
+ nestedScrollAxis |= View.SCROLL_AXIS_HORIZONTAL;
+ }
+ if (canScrollVertically) {
+ nestedScrollAxis |= View.SCROLL_AXIS_VERTICAL;
+ }
+ startNestedScroll(nestedScrollAxis);
+ break;
+
+ case MotionEvent.ACTION_POINTER_DOWN:
+ mScrollPointerId = e.getPointerId(actionIndex);
+ mInitialTouchX = mLastTouchX = (int) (e.getX(actionIndex) + 0.5f);
+ mInitialTouchY = mLastTouchY = (int) (e.getY(actionIndex) + 0.5f);
+ break;
+
+ case MotionEvent.ACTION_MOVE: {
+ final int index = e.findPointerIndex(mScrollPointerId);
+ if (index < 0) {
+ Log.e(TAG, "Error processing scroll; pointer index for id "
+ + mScrollPointerId + " not found. Did any MotionEvents get skipped?");
+ return false;
+ }
+
+ final int x = (int) (e.getX(index) + 0.5f);
+ final int y = (int) (e.getY(index) + 0.5f);
+ if (mScrollState != SCROLL_STATE_DRAGGING) {
+ final int dx = x - mInitialTouchX;
+ final int dy = y - mInitialTouchY;
+ boolean startScroll = false;
+ if (canScrollHorizontally && Math.abs(dx) > mTouchSlop) {
+ mLastTouchX = mInitialTouchX + mTouchSlop * (dx < 0 ? -1 : 1);
+ startScroll = true;
+ }
+ if (canScrollVertically && Math.abs(dy) > mTouchSlop) {
+ mLastTouchY = mInitialTouchY + mTouchSlop * (dy < 0 ? -1 : 1);
+ startScroll = true;
+ }
+ if (startScroll) {
+ setScrollState(SCROLL_STATE_DRAGGING);
+ }
+ }
+ } break;
+
+ case MotionEvent.ACTION_POINTER_UP: {
+ onPointerUp(e);
+ } break;
+
+ case MotionEvent.ACTION_UP: {
+ mVelocityTracker.clear();
+ stopNestedScroll();
+ } break;
+
+ case MotionEvent.ACTION_CANCEL: {
+ cancelTouch();
+ }
+ }
+ return mScrollState == SCROLL_STATE_DRAGGING;
+ }
+
+ @Override
+ public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {
+ final int listenerCount = mOnItemTouchListeners.size();
+ for (int i = 0; i < listenerCount; i++) {
+ final OnItemTouchListener listener = mOnItemTouchListeners.get(i);
+ listener.onRequestDisallowInterceptTouchEvent(disallowIntercept);
+ }
+ super.requestDisallowInterceptTouchEvent(disallowIntercept);
+ }
+
+ @Override
+ public boolean onTouchEvent(MotionEvent e) {
+ if (mLayoutFrozen || mIgnoreMotionEventTillDown) {
+ return false;
+ }
+ if (dispatchOnItemTouch(e)) {
+ cancelTouch();
+ return true;
+ }
+
+ if (mLayout == null) {
+ return false;
+ }
+
+ final boolean canScrollHorizontally = mLayout.canScrollHorizontally();
+ final boolean canScrollVertically = mLayout.canScrollVertically();
+
+ if (mVelocityTracker == null) {
+ mVelocityTracker = VelocityTracker.obtain();
+ }
+ boolean eventAddedToVelocityTracker = false;
+
+ final MotionEvent vtev = MotionEvent.obtain(e);
+ final int action = e.getActionMasked();
+ final int actionIndex = e.getActionIndex();
+
+ if (action == MotionEvent.ACTION_DOWN) {
+ mNestedOffsets[0] = mNestedOffsets[1] = 0;
+ }
+ vtev.offsetLocation(mNestedOffsets[0], mNestedOffsets[1]);
+
+ switch (action) {
+ case MotionEvent.ACTION_DOWN: {
+ mScrollPointerId = e.getPointerId(0);
+ mInitialTouchX = mLastTouchX = (int) (e.getX() + 0.5f);
+ mInitialTouchY = mLastTouchY = (int) (e.getY() + 0.5f);
+
+ int nestedScrollAxis = View.SCROLL_AXIS_NONE;
+ if (canScrollHorizontally) {
+ nestedScrollAxis |= View.SCROLL_AXIS_HORIZONTAL;
+ }
+ if (canScrollVertically) {
+ nestedScrollAxis |= View.SCROLL_AXIS_VERTICAL;
+ }
+ startNestedScroll(nestedScrollAxis);
+ } break;
+
+ case MotionEvent.ACTION_POINTER_DOWN: {
+ mScrollPointerId = e.getPointerId(actionIndex);
+ mInitialTouchX = mLastTouchX = (int) (e.getX(actionIndex) + 0.5f);
+ mInitialTouchY = mLastTouchY = (int) (e.getY(actionIndex) + 0.5f);
+ } break;
+
+ case MotionEvent.ACTION_MOVE: {
+ final int index = e.findPointerIndex(mScrollPointerId);
+ if (index < 0) {
+ Log.e(TAG, "Error processing scroll; pointer index for id "
+ + mScrollPointerId + " not found. Did any MotionEvents get skipped?");
+ return false;
+ }
+
+ final int x = (int) (e.getX(index) + 0.5f);
+ final int y = (int) (e.getY(index) + 0.5f);
+ int dx = mLastTouchX - x;
+ int dy = mLastTouchY - y;
+
+ if (dispatchNestedPreScroll(dx, dy, mScrollConsumed, mScrollOffset)) {
+ dx -= mScrollConsumed[0];
+ dy -= mScrollConsumed[1];
+ vtev.offsetLocation(mScrollOffset[0], mScrollOffset[1]);
+ // Updated the nested offsets
+ mNestedOffsets[0] += mScrollOffset[0];
+ mNestedOffsets[1] += mScrollOffset[1];
+ }
+
+ if (mScrollState != SCROLL_STATE_DRAGGING) {
+ boolean startScroll = false;
+ if (canScrollHorizontally && Math.abs(dx) > mTouchSlop) {
+ if (dx > 0) {
+ dx -= mTouchSlop;
+ } else {
+ dx += mTouchSlop;
+ }
+ startScroll = true;
+ }
+ if (canScrollVertically && Math.abs(dy) > mTouchSlop) {
+ if (dy > 0) {
+ dy -= mTouchSlop;
+ } else {
+ dy += mTouchSlop;
+ }
+ startScroll = true;
+ }
+ if (startScroll) {
+ setScrollState(SCROLL_STATE_DRAGGING);
+ }
+ }
+
+ if (mScrollState == SCROLL_STATE_DRAGGING) {
+ mLastTouchX = x - mScrollOffset[0];
+ mLastTouchY = y - mScrollOffset[1];
+
+ if (scrollByInternal(
+ canScrollHorizontally ? dx : 0,
+ canScrollVertically ? dy : 0,
+ vtev)) {
+ getParent().requestDisallowInterceptTouchEvent(true);
+ }
+ if (mGapWorker != null && (dx != 0 || dy != 0)) {
+ mGapWorker.postFromTraversal(this, dx, dy);
+ }
+ }
+ } break;
+
+ case MotionEvent.ACTION_POINTER_UP: {
+ onPointerUp(e);
+ } break;
+
+ case MotionEvent.ACTION_UP: {
+ mVelocityTracker.addMovement(vtev);
+ eventAddedToVelocityTracker = true;
+ mVelocityTracker.computeCurrentVelocity(1000, mMaxFlingVelocity);
+ final float xvel = canScrollHorizontally
+ ? -mVelocityTracker.getXVelocity(mScrollPointerId) : 0;
+ final float yvel = canScrollVertically
+ ? -mVelocityTracker.getYVelocity(mScrollPointerId) : 0;
+ if (!((xvel != 0 || yvel != 0) && fling((int) xvel, (int) yvel))) {
+ setScrollState(SCROLL_STATE_IDLE);
+ }
+ resetTouch();
+ } break;
+
+ case MotionEvent.ACTION_CANCEL: {
+ cancelTouch();
+ } break;
+ }
+
+ if (!eventAddedToVelocityTracker) {
+ mVelocityTracker.addMovement(vtev);
+ }
+ vtev.recycle();
+
+ return true;
+ }
+
+ private void resetTouch() {
+ if (mVelocityTracker != null) {
+ mVelocityTracker.clear();
+ }
+ stopNestedScroll();
+ releaseGlows();
+ }
+
+ private void cancelTouch() {
+ resetTouch();
+ setScrollState(SCROLL_STATE_IDLE);
+ }
+
+ private void onPointerUp(MotionEvent e) {
+ final int actionIndex = e.getActionIndex();
+ if (e.getPointerId(actionIndex) == mScrollPointerId) {
+ // Pick a new pointer to pick up the slack.
+ final int newIndex = actionIndex == 0 ? 1 : 0;
+ mScrollPointerId = e.getPointerId(newIndex);
+ mInitialTouchX = mLastTouchX = (int) (e.getX(newIndex) + 0.5f);
+ mInitialTouchY = mLastTouchY = (int) (e.getY(newIndex) + 0.5f);
+ }
+ }
+
+ // @Override
+ public boolean onGenericMotionEvent(MotionEvent event) {
+ if (mLayout == null) {
+ return false;
+ }
+ if (mLayoutFrozen) {
+ return false;
+ }
+ if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) {
+ if (event.getAction() == MotionEvent.ACTION_SCROLL) {
+ final float vScroll, hScroll;
+ if (mLayout.canScrollVertically()) {
+ // Inverse the sign of the vertical scroll to align the scroll orientation
+ // with AbsListView.
+ vScroll = -event.getAxisValue(MotionEvent.AXIS_VSCROLL);
+ } else {
+ vScroll = 0f;
+ }
+ if (mLayout.canScrollHorizontally()) {
+ hScroll = event.getAxisValue(MotionEvent.AXIS_HSCROLL);
+ } else {
+ hScroll = 0f;
+ }
+
+ if (vScroll != 0 || hScroll != 0) {
+ final float scrollFactor = getScrollFactor();
+ scrollByInternal((int) (hScroll * scrollFactor),
+ (int) (vScroll * scrollFactor), event);
+ }
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Ported from View.getVerticalScrollFactor.
+ */
+ private float getScrollFactor() {
+ if (mScrollFactor == Float.MIN_VALUE) {
+ TypedValue outValue = new TypedValue();
+ if (getContext().getTheme().resolveAttribute(
+ android.R.attr.listPreferredItemHeight, outValue, true)) {
+ mScrollFactor = outValue.getDimension(
+ getContext().getResources().getDisplayMetrics());
+ } else {
+ return 0; //listPreferredItemHeight is not defined, no generic scrolling
+ }
+ }
+ return mScrollFactor;
+ }
+
+ @Override
+ protected void onMeasure(int widthSpec, int heightSpec) {
+ if (mLayout == null) {
+ defaultOnMeasure(widthSpec, heightSpec);
+ return;
+ }
+ if (mLayout.mAutoMeasure) {
+ final int widthMode = MeasureSpec.getMode(widthSpec);
+ final int heightMode = MeasureSpec.getMode(heightSpec);
+ final boolean skipMeasure = widthMode == MeasureSpec.EXACTLY
+ && heightMode == MeasureSpec.EXACTLY;
+ mLayout.onMeasure(mRecycler, mState, widthSpec, heightSpec);
+ if (skipMeasure || mAdapter == null) {
+ return;
+ }
+ if (mState.mLayoutStep == State.STEP_START) {
+ dispatchLayoutStep1();
+ }
+ // set dimensions in 2nd step. Pre-layout should happen with old dimensions for
+ // consistency
+ mLayout.setMeasureSpecs(widthSpec, heightSpec);
+ mState.mIsMeasuring = true;
+ dispatchLayoutStep2();
+
+ // now we can get the width and height from the children.
+ mLayout.setMeasuredDimensionFromChildren(widthSpec, heightSpec);
+
+ // if RecyclerView has non-exact width and height and if there is at least one child
+ // which also has non-exact width & height, we have to re-measure.
+ if (mLayout.shouldMeasureTwice()) {
+ mLayout.setMeasureSpecs(
+ MeasureSpec.makeMeasureSpec(getMeasuredWidth(), MeasureSpec.EXACTLY),
+ MeasureSpec.makeMeasureSpec(getMeasuredHeight(), MeasureSpec.EXACTLY));
+ mState.mIsMeasuring = true;
+ dispatchLayoutStep2();
+ // now we can get the width and height from the children.
+ mLayout.setMeasuredDimensionFromChildren(widthSpec, heightSpec);
+ }
+ } else {
+ if (mHasFixedSize) {
+ mLayout.onMeasure(mRecycler, mState, widthSpec, heightSpec);
+ return;
+ }
+ // custom onMeasure
+ if (mAdapterUpdateDuringMeasure) {
+ eatRequestLayout();
+ onEnterLayoutOrScroll();
+ processAdapterUpdatesAndSetAnimationFlags();
+ onExitLayoutOrScroll();
+
+ if (mState.mRunPredictiveAnimations) {
+ mState.mInPreLayout = true;
+ } else {
+ // consume remaining updates to provide a consistent state with the layout pass.
+ mAdapterHelper.consumeUpdatesInOnePass();
+ mState.mInPreLayout = false;
+ }
+ mAdapterUpdateDuringMeasure = false;
+ resumeRequestLayout(false);
+ }
+
+ if (mAdapter != null) {
+ mState.mItemCount = mAdapter.getItemCount();
+ } else {
+ mState.mItemCount = 0;
+ }
+ eatRequestLayout();
+ mLayout.onMeasure(mRecycler, mState, widthSpec, heightSpec);
+ resumeRequestLayout(false);
+ mState.mInPreLayout = false; // clear
+ }
+ }
+
+ /**
+ * Used when onMeasure is called before layout manager is set
+ */
+ void defaultOnMeasure(int widthSpec, int heightSpec) {
+ // calling LayoutManager here is not pretty but that API is already public and it is better
+ // than creating another method since this is internal.
+ final int width = LayoutManager.chooseSize(widthSpec,
+ getPaddingLeft() + getPaddingRight(),
+ getMinimumWidth());
+ final int height = LayoutManager.chooseSize(heightSpec,
+ getPaddingTop() + getPaddingBottom(),
+ getMinimumHeight());
+
+ setMeasuredDimension(width, height);
+ }
+
+ @Override
+ protected void onSizeChanged(int w, int h, int oldw, int oldh) {
+ super.onSizeChanged(w, h, oldw, oldh);
+ if (w != oldw || h != oldh) {
+ invalidateGlows();
+ // layout's w/h are updated during measure/layout steps.
+ }
+ }
+
+ /**
+ * Sets the {@link ItemAnimator} that will handle animations involving changes
+ * to the items in this RecyclerView. By default, RecyclerView instantiates and
+ * uses an instance of {@link DefaultItemAnimator}. Whether item animations are
+ * enabled for the RecyclerView depends on the ItemAnimator and whether
+ * the LayoutManager {@link LayoutManager#supportsPredictiveItemAnimations()
+ * supports item animations}.
+ *
+ * @param animator The ItemAnimator being set. If null, no animations will occur
+ * when changes occur to the items in this RecyclerView.
+ */
+ public void setItemAnimator(ItemAnimator animator) {
+ if (mItemAnimator != null) {
+ mItemAnimator.endAnimations();
+ mItemAnimator.setListener(null);
+ }
+ mItemAnimator = animator;
+ if (mItemAnimator != null) {
+ mItemAnimator.setListener(mItemAnimatorListener);
+ }
+ }
+
+ void onEnterLayoutOrScroll() {
+ mLayoutOrScrollCounter++;
+ }
+
+ void onExitLayoutOrScroll() {
+ mLayoutOrScrollCounter--;
+ if (mLayoutOrScrollCounter < 1) {
+ if (DEBUG && mLayoutOrScrollCounter < 0) {
+ throw new IllegalStateException("layout or scroll counter cannot go below zero."
+ + "Some calls are not matching");
+ }
+ mLayoutOrScrollCounter = 0;
+ dispatchContentChangedIfNecessary();
+ dispatchPendingImportantForAccessibilityChanges();
+ }
+ }
+
+ boolean isAccessibilityEnabled() {
+ return mAccessibilityManager != null && mAccessibilityManager.isEnabled();
+ }
+
+ private void dispatchContentChangedIfNecessary() {
+ final int flags = mEatenAccessibilityChangeFlags;
+ mEatenAccessibilityChangeFlags = 0;
+ if (flags != 0 && isAccessibilityEnabled()) {
+ final AccessibilityEvent event = AccessibilityEvent.obtain();
+ event.setEventType(AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED);
+ event.setContentChangeTypes(flags);
+ sendAccessibilityEventUnchecked(event);
+ }
+ }
+
+ /**
+ * Returns whether RecyclerView is currently computing a layout.
+ * <p>
+ * If this method returns true, it means that RecyclerView is in a lockdown state and any
+ * attempt to update adapter contents will result in an exception because adapter contents
+ * cannot be changed while RecyclerView is trying to compute the layout.
+ * <p>
+ * It is very unlikely that your code will be running during this state as it is
+ * called by the framework when a layout traversal happens or RecyclerView starts to scroll
+ * in response to system events (touch, accessibility etc).
+ * <p>
+ * This case may happen if you have some custom logic to change adapter contents in
+ * response to a View callback (e.g. focus change callback) which might be triggered during a
+ * layout calculation. In these cases, you should just postpone the change using a Handler or a
+ * similar mechanism.
+ *
+ * @return <code>true</code> if RecyclerView is currently computing a layout, <code>false</code>
+ * otherwise
+ */
+ public boolean isComputingLayout() {
+ return mLayoutOrScrollCounter > 0;
+ }
+
+ /**
+ * Returns true if an accessibility event should not be dispatched now. This happens when an
+ * accessibility request arrives while RecyclerView does not have a stable state which is very
+ * hard to handle for a LayoutManager. Instead, this method records necessary information about
+ * the event and dispatches a window change event after the critical section is finished.
+ *
+ * @return True if the accessibility event should be postponed.
+ */
+ boolean shouldDeferAccessibilityEvent(AccessibilityEvent event) {
+ if (isComputingLayout()) {
+ int type = 0;
+ if (event != null) {
+ type = event.getContentChangeTypes();
+ }
+ if (type == 0) {
+ type = AccessibilityEvent.CONTENT_CHANGE_TYPE_UNDEFINED;
+ }
+ mEatenAccessibilityChangeFlags |= type;
+ return true;
+ }
+ return false;
+ }
+
+ @Override
+ public void sendAccessibilityEventUnchecked(AccessibilityEvent event) {
+ if (shouldDeferAccessibilityEvent(event)) {
+ return;
+ }
+ super.sendAccessibilityEventUnchecked(event);
+ }
+
+ /**
+ * Gets the current ItemAnimator for this RecyclerView. A null return value
+ * indicates that there is no animator and that item changes will happen without
+ * any animations. By default, RecyclerView instantiates and
+ * uses an instance of {@link DefaultItemAnimator}.
+ *
+ * @return ItemAnimator The current ItemAnimator. If null, no animations will occur
+ * when changes occur to the items in this RecyclerView.
+ */
+ public ItemAnimator getItemAnimator() {
+ return mItemAnimator;
+ }
+
+ /**
+ * Post a runnable to the next frame to run pending item animations. Only the first such
+ * request will be posted, governed by the mPostedAnimatorRunner flag.
+ */
+ void postAnimationRunner() {
+ if (!mPostedAnimatorRunner && mIsAttached) {
+ postOnAnimation(mItemAnimatorRunner);
+ mPostedAnimatorRunner = true;
+ }
+ }
+
+ private boolean predictiveItemAnimationsEnabled() {
+ return (mItemAnimator != null && mLayout.supportsPredictiveItemAnimations());
+ }
+
+ /**
+ * Consumes adapter updates and calculates which type of animations we want to run.
+ * Called in onMeasure and dispatchLayout.
+ * <p>
+ * This method may process only the pre-layout state of updates or all of them.
+ */
+ private void processAdapterUpdatesAndSetAnimationFlags() {
+ if (mDataSetHasChangedAfterLayout) {
+ // Processing these items have no value since data set changed unexpectedly.
+ // Instead, we just reset it.
+ mAdapterHelper.reset();
+ mLayout.onItemsChanged(this);
+ }
+ // simple animations are a subset of advanced animations (which will cause a
+ // pre-layout step)
+ // If layout supports predictive animations, pre-process to decide if we want to run them
+ if (predictiveItemAnimationsEnabled()) {
+ mAdapterHelper.preProcess();
+ } else {
+ mAdapterHelper.consumeUpdatesInOnePass();
+ }
+ boolean animationTypeSupported = mItemsAddedOrRemoved || mItemsChanged;
+ mState.mRunSimpleAnimations = mFirstLayoutComplete
+ && mItemAnimator != null
+ && (mDataSetHasChangedAfterLayout
+ || animationTypeSupported
+ || mLayout.mRequestedSimpleAnimations)
+ && (!mDataSetHasChangedAfterLayout
+ || mAdapter.hasStableIds());
+ mState.mRunPredictiveAnimations = mState.mRunSimpleAnimations
+ && animationTypeSupported
+ && !mDataSetHasChangedAfterLayout
+ && predictiveItemAnimationsEnabled();
+ }
+
+ /**
+ * Wrapper around layoutChildren() that handles animating changes caused by layout.
+ * Animations work on the assumption that there are five different kinds of items
+ * in play:
+ * PERSISTENT: items are visible before and after layout
+ * REMOVED: items were visible before layout and were removed by the app
+ * ADDED: items did not exist before layout and were added by the app
+ * DISAPPEARING: items exist in the data set before/after, but changed from
+ * visible to non-visible in the process of layout (they were moved off
+ * screen as a side-effect of other changes)
+ * APPEARING: items exist in the data set before/after, but changed from
+ * non-visible to visible in the process of layout (they were moved on
+ * screen as a side-effect of other changes)
+ * The overall approach figures out what items exist before/after layout and
+ * infers one of the five above states for each of the items. Then the animations
+ * are set up accordingly:
+ * PERSISTENT views are animated via
+ * {@link ItemAnimator#animatePersistence(ViewHolder, ItemHolderInfo, ItemHolderInfo)}
+ * DISAPPEARING views are animated via
+ * {@link ItemAnimator#animateDisappearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)}
+ * APPEARING views are animated via
+ * {@link ItemAnimator#animateAppearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)}
+ * and changed views are animated via
+ * {@link ItemAnimator#animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)}.
+ */
+ void dispatchLayout() {
+ if (mAdapter == null) {
+ Log.e(TAG, "No adapter attached; skipping layout");
+ // leave the state in START
+ return;
+ }
+ if (mLayout == null) {
+ Log.e(TAG, "No layout manager attached; skipping layout");
+ // leave the state in START
+ return;
+ }
+ mState.mIsMeasuring = false;
+ if (mState.mLayoutStep == State.STEP_START) {
+ dispatchLayoutStep1();
+ mLayout.setExactMeasureSpecsFrom(this);
+ dispatchLayoutStep2();
+ } else if (mAdapterHelper.hasUpdates() || mLayout.getWidth() != getWidth()
+ || mLayout.getHeight() != getHeight()) {
+ // First 2 steps are done in onMeasure but looks like we have to run again due to
+ // changed size.
+ mLayout.setExactMeasureSpecsFrom(this);
+ dispatchLayoutStep2();
+ } else {
+ // always make sure we sync them (to ensure mode is exact)
+ mLayout.setExactMeasureSpecsFrom(this);
+ }
+ dispatchLayoutStep3();
+ }
+
+ private void saveFocusInfo() {
+ View child = null;
+ if (mPreserveFocusAfterLayout && hasFocus() && mAdapter != null) {
+ child = getFocusedChild();
+ }
+
+ final ViewHolder focusedVh = child == null ? null : findContainingViewHolder(child);
+ if (focusedVh == null) {
+ resetFocusInfo();
+ } else {
+ mState.mFocusedItemId = mAdapter.hasStableIds() ? focusedVh.getItemId() : NO_ID;
+ // mFocusedItemPosition should hold the current adapter position of the previously
+ // focused item. If the item is removed, we store the previous adapter position of the
+ // removed item.
+ mState.mFocusedItemPosition = mDataSetHasChangedAfterLayout ? NO_POSITION
+ : (focusedVh.isRemoved() ? focusedVh.mOldPosition
+ : focusedVh.getAdapterPosition());
+ mState.mFocusedSubChildId = getDeepestFocusedViewWithId(focusedVh.itemView);
+ }
+ }
+
+ private void resetFocusInfo() {
+ mState.mFocusedItemId = NO_ID;
+ mState.mFocusedItemPosition = NO_POSITION;
+ mState.mFocusedSubChildId = View.NO_ID;
+ }
+
+ /**
+ * Finds the best view candidate to request focus on using mFocusedItemPosition index of the
+ * previously focused item. It first traverses the adapter forward to find a focusable candidate
+ * and if no such candidate is found, it reverses the focus search direction for the items
+ * before the mFocusedItemPosition'th index;
+ * @return The best candidate to request focus on, or null if no such candidate exists. Null
+ * indicates all the existing adapter items are unfocusable.
+ */
+ @Nullable
+ private View findNextViewToFocus() {
+ int startFocusSearchIndex = mState.mFocusedItemPosition != -1 ? mState.mFocusedItemPosition
+ : 0;
+ ViewHolder nextFocus;
+ final int itemCount = mState.getItemCount();
+ for (int i = startFocusSearchIndex; i < itemCount; i++) {
+ nextFocus = findViewHolderForAdapterPosition(i);
+ if (nextFocus == null) {
+ break;
+ }
+ if (nextFocus.itemView.hasFocusable()) {
+ return nextFocus.itemView;
+ }
+ }
+ final int limit = Math.min(itemCount, startFocusSearchIndex);
+ for (int i = limit - 1; i >= 0; i--) {
+ nextFocus = findViewHolderForAdapterPosition(i);
+ if (nextFocus == null) {
+ return null;
+ }
+ if (nextFocus.itemView.hasFocusable()) {
+ return nextFocus.itemView;
+ }
+ }
+ return null;
+ }
+
+ private void recoverFocusFromState() {
+ if (!mPreserveFocusAfterLayout || mAdapter == null || !hasFocus()
+ || getDescendantFocusability() == FOCUS_BLOCK_DESCENDANTS
+ || (getDescendantFocusability() == FOCUS_BEFORE_DESCENDANTS && isFocused())) {
+ // No-op if either of these cases happens:
+ // 1. RV has no focus, or 2. RV blocks focus to its children, or 3. RV takes focus
+ // before its children and is focused (i.e. it already stole the focus away from its
+ // descendants).
+ return;
+ }
+ // only recover focus if RV itself has the focus or the focused view is hidden
+ if (!isFocused()) {
+ final View focusedChild = getFocusedChild();
+ if (IGNORE_DETACHED_FOCUSED_CHILD
+ && (focusedChild.getParent() == null || !focusedChild.hasFocus())) {
+ // Special handling of API 15-. A focused child can be invalid because mFocus is not
+ // cleared when the child is detached (mParent = null),
+ // This happens because clearFocus on API 15- does not invalidate mFocus of its
+ // parent when this child is detached.
+ // For API 16+, this is not an issue because requestFocus takes care of clearing the
+ // prior detached focused child. For API 15- the problem happens in 2 cases because
+ // clearChild does not call clearChildFocus on RV: 1. setFocusable(false) is called
+ // for the current focused item which calls clearChild or 2. when the prior focused
+ // child is removed, removeDetachedView called in layout step 3 which calls
+ // clearChild. We should ignore this invalid focused child in all our calculations
+ // for the next view to receive focus, and apply the focus recovery logic instead.
+ if (mChildHelper.getChildCount() == 0) {
+ // No children left. Request focus on the RV itself since one of its children
+ // was holding focus previously.
+ requestFocus();
+ return;
+ }
+ } else if (!mChildHelper.isHidden(focusedChild)) {
+ // If the currently focused child is hidden, apply the focus recovery logic.
+ // Otherwise return, i.e. the currently (unhidden) focused child is good enough :/.
+ return;
+ }
+ }
+ ViewHolder focusTarget = null;
+ // RV first attempts to locate the previously focused item to request focus on using
+ // mFocusedItemId. If such an item no longer exists, it then makes a best-effort attempt to
+ // find the next best candidate to request focus on based on mFocusedItemPosition.
+ if (mState.mFocusedItemId != NO_ID && mAdapter.hasStableIds()) {
+ focusTarget = findViewHolderForItemId(mState.mFocusedItemId);
+ }
+ View viewToFocus = null;
+ if (focusTarget == null || mChildHelper.isHidden(focusTarget.itemView)
+ || !focusTarget.itemView.hasFocusable()) {
+ if (mChildHelper.getChildCount() > 0) {
+ // At this point, RV has focus and either of these conditions are true:
+ // 1. There's no previously focused item either because RV received focused before
+ // layout, or the previously focused item was removed, or RV doesn't have stable IDs
+ // 2. Previous focus child is hidden, or 3. Previous focused child is no longer
+ // focusable. In either of these cases, we make sure that RV still passes down the
+ // focus to one of its focusable children using a best-effort algorithm.
+ viewToFocus = findNextViewToFocus();
+ }
+ } else {
+ // looks like the focused item has been replaced with another view that represents the
+ // same item in the adapter. Request focus on that.
+ viewToFocus = focusTarget.itemView;
+ }
+
+ if (viewToFocus != null) {
+ if (mState.mFocusedSubChildId != NO_ID) {
+ View child = viewToFocus.findViewById(mState.mFocusedSubChildId);
+ if (child != null && child.isFocusable()) {
+ viewToFocus = child;
+ }
+ }
+ viewToFocus.requestFocus();
+ }
+ }
+
+ private int getDeepestFocusedViewWithId(View view) {
+ int lastKnownId = view.getId();
+ while (!view.isFocused() && view instanceof ViewGroup && view.hasFocus()) {
+ view = ((ViewGroup) view).getFocusedChild();
+ final int id = view.getId();
+ if (id != View.NO_ID) {
+ lastKnownId = view.getId();
+ }
+ }
+ return lastKnownId;
+ }
+
+ /**
+ * The first step of a layout where we;
+ * - process adapter updates
+ * - decide which animation should run
+ * - save information about current views
+ * - If necessary, run predictive layout and save its information
+ */
+ private void dispatchLayoutStep1() {
+ mState.assertLayoutStep(State.STEP_START);
+ mState.mIsMeasuring = false;
+ eatRequestLayout();
+ mViewInfoStore.clear();
+ onEnterLayoutOrScroll();
+ processAdapterUpdatesAndSetAnimationFlags();
+ saveFocusInfo();
+ mState.mTrackOldChangeHolders = mState.mRunSimpleAnimations && mItemsChanged;
+ mItemsAddedOrRemoved = mItemsChanged = false;
+ mState.mInPreLayout = mState.mRunPredictiveAnimations;
+ mState.mItemCount = mAdapter.getItemCount();
+ findMinMaxChildLayoutPositions(mMinMaxLayoutPositions);
+
+ if (mState.mRunSimpleAnimations) {
+ // Step 0: Find out where all non-removed items are, pre-layout
+ int count = mChildHelper.getChildCount();
+ for (int i = 0; i < count; ++i) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getChildAt(i));
+ if (holder.shouldIgnore() || (holder.isInvalid() && !mAdapter.hasStableIds())) {
+ continue;
+ }
+ final ItemHolderInfo animationInfo = mItemAnimator
+ .recordPreLayoutInformation(mState, holder,
+ ItemAnimator.buildAdapterChangeFlagsForAnimations(holder),
+ holder.getUnmodifiedPayloads());
+ mViewInfoStore.addToPreLayout(holder, animationInfo);
+ if (mState.mTrackOldChangeHolders && holder.isUpdated() && !holder.isRemoved()
+ && !holder.shouldIgnore() && !holder.isInvalid()) {
+ long key = getChangedHolderKey(holder);
+ // This is NOT the only place where a ViewHolder is added to old change holders
+ // list. There is another case where:
+ // * A VH is currently hidden but not deleted
+ // * The hidden item is changed in the adapter
+ // * Layout manager decides to layout the item in the pre-Layout pass (step1)
+ // When this case is detected, RV will un-hide that view and add to the old
+ // change holders list.
+ mViewInfoStore.addToOldChangeHolders(key, holder);
+ }
+ }
+ }
+ if (mState.mRunPredictiveAnimations) {
+ // Step 1: run prelayout: This will use the old positions of items. The layout manager
+ // is expected to layout everything, even removed items (though not to add removed
+ // items back to the container). This gives the pre-layout position of APPEARING views
+ // which come into existence as part of the real layout.
+
+ // Save old positions so that LayoutManager can run its mapping logic.
+ saveOldPositions();
+ final boolean didStructureChange = mState.mStructureChanged;
+ mState.mStructureChanged = false;
+ // temporarily disable flag because we are asking for previous layout
+ mLayout.onLayoutChildren(mRecycler, mState);
+ mState.mStructureChanged = didStructureChange;
+
+ for (int i = 0; i < mChildHelper.getChildCount(); ++i) {
+ final View child = mChildHelper.getChildAt(i);
+ final ViewHolder viewHolder = getChildViewHolderInt(child);
+ if (viewHolder.shouldIgnore()) {
+ continue;
+ }
+ if (!mViewInfoStore.isInPreLayout(viewHolder)) {
+ int flags = ItemAnimator.buildAdapterChangeFlagsForAnimations(viewHolder);
+ boolean wasHidden = viewHolder
+ .hasAnyOfTheFlags(ViewHolder.FLAG_BOUNCED_FROM_HIDDEN_LIST);
+ if (!wasHidden) {
+ flags |= ItemAnimator.FLAG_APPEARED_IN_PRE_LAYOUT;
+ }
+ final ItemHolderInfo animationInfo = mItemAnimator.recordPreLayoutInformation(
+ mState, viewHolder, flags, viewHolder.getUnmodifiedPayloads());
+ if (wasHidden) {
+ recordAnimationInfoIfBouncedHiddenView(viewHolder, animationInfo);
+ } else {
+ mViewInfoStore.addToAppearedInPreLayoutHolders(viewHolder, animationInfo);
+ }
+ }
+ }
+ // we don't process disappearing list because they may re-appear in post layout pass.
+ clearOldPositions();
+ } else {
+ clearOldPositions();
+ }
+ onExitLayoutOrScroll();
+ resumeRequestLayout(false);
+ mState.mLayoutStep = State.STEP_LAYOUT;
+ }
+
+ /**
+ * The second layout step where we do the actual layout of the views for the final state.
+ * This step might be run multiple times if necessary (e.g. measure).
+ */
+ private void dispatchLayoutStep2() {
+ eatRequestLayout();
+ onEnterLayoutOrScroll();
+ mState.assertLayoutStep(State.STEP_LAYOUT | State.STEP_ANIMATIONS);
+ mAdapterHelper.consumeUpdatesInOnePass();
+ mState.mItemCount = mAdapter.getItemCount();
+ mState.mDeletedInvisibleItemCountSincePreviousLayout = 0;
+
+ // Step 2: Run layout
+ mState.mInPreLayout = false;
+ mLayout.onLayoutChildren(mRecycler, mState);
+
+ mState.mStructureChanged = false;
+ mPendingSavedState = null;
+
+ // onLayoutChildren may have caused client code to disable item animations; re-check
+ mState.mRunSimpleAnimations = mState.mRunSimpleAnimations && mItemAnimator != null;
+ mState.mLayoutStep = State.STEP_ANIMATIONS;
+ onExitLayoutOrScroll();
+ resumeRequestLayout(false);
+ }
+
+ /**
+ * The final step of the layout where we save the information about views for animations,
+ * trigger animations and do any necessary cleanup.
+ */
+ private void dispatchLayoutStep3() {
+ mState.assertLayoutStep(State.STEP_ANIMATIONS);
+ eatRequestLayout();
+ onEnterLayoutOrScroll();
+ mState.mLayoutStep = State.STEP_START;
+ if (mState.mRunSimpleAnimations) {
+ // Step 3: Find out where things are now, and process change animations.
+ // traverse list in reverse because we may call animateChange in the loop which may
+ // remove the target view holder.
+ for (int i = mChildHelper.getChildCount() - 1; i >= 0; i--) {
+ ViewHolder holder = getChildViewHolderInt(mChildHelper.getChildAt(i));
+ if (holder.shouldIgnore()) {
+ continue;
+ }
+ long key = getChangedHolderKey(holder);
+ final ItemHolderInfo animationInfo = mItemAnimator
+ .recordPostLayoutInformation(mState, holder);
+ ViewHolder oldChangeViewHolder = mViewInfoStore.getFromOldChangeHolders(key);
+ if (oldChangeViewHolder != null && !oldChangeViewHolder.shouldIgnore()) {
+ // run a change animation
+
+ // If an Item is CHANGED but the updated version is disappearing, it creates
+ // a conflicting case.
+ // Since a view that is marked as disappearing is likely to be going out of
+ // bounds, we run a change animation. Both views will be cleaned automatically
+ // once their animations finish.
+ // On the other hand, if it is the same view holder instance, we run a
+ // disappearing animation instead because we are not going to rebind the updated
+ // VH unless it is enforced by the layout manager.
+ final boolean oldDisappearing = mViewInfoStore.isDisappearing(
+ oldChangeViewHolder);
+ final boolean newDisappearing = mViewInfoStore.isDisappearing(holder);
+ if (oldDisappearing && oldChangeViewHolder == holder) {
+ // run disappear animation instead of change
+ mViewInfoStore.addToPostLayout(holder, animationInfo);
+ } else {
+ final ItemHolderInfo preInfo = mViewInfoStore.popFromPreLayout(
+ oldChangeViewHolder);
+ // we add and remove so that any post info is merged.
+ mViewInfoStore.addToPostLayout(holder, animationInfo);
+ ItemHolderInfo postInfo = mViewInfoStore.popFromPostLayout(holder);
+ if (preInfo == null) {
+ handleMissingPreInfoForChangeError(key, holder, oldChangeViewHolder);
+ } else {
+ animateChange(oldChangeViewHolder, holder, preInfo, postInfo,
+ oldDisappearing, newDisappearing);
+ }
+ }
+ } else {
+ mViewInfoStore.addToPostLayout(holder, animationInfo);
+ }
+ }
+
+ // Step 4: Process view info lists and trigger animations
+ mViewInfoStore.process(mViewInfoProcessCallback);
+ }
+
+ mLayout.removeAndRecycleScrapInt(mRecycler);
+ mState.mPreviousLayoutItemCount = mState.mItemCount;
+ mDataSetHasChangedAfterLayout = false;
+ mState.mRunSimpleAnimations = false;
+
+ mState.mRunPredictiveAnimations = false;
+ mLayout.mRequestedSimpleAnimations = false;
+ if (mRecycler.mChangedScrap != null) {
+ mRecycler.mChangedScrap.clear();
+ }
+ if (mLayout.mPrefetchMaxObservedInInitialPrefetch) {
+ // Initial prefetch has expanded cache, so reset until next prefetch.
+ // This prevents initial prefetches from expanding the cache permanently.
+ mLayout.mPrefetchMaxCountObserved = 0;
+ mLayout.mPrefetchMaxObservedInInitialPrefetch = false;
+ mRecycler.updateViewCacheSize();
+ }
+
+ mLayout.onLayoutCompleted(mState);
+ onExitLayoutOrScroll();
+ resumeRequestLayout(false);
+ mViewInfoStore.clear();
+ if (didChildRangeChange(mMinMaxLayoutPositions[0], mMinMaxLayoutPositions[1])) {
+ dispatchOnScrolled(0, 0);
+ }
+ recoverFocusFromState();
+ resetFocusInfo();
+ }
+
+ /**
+ * This handles the case where there is an unexpected VH missing in the pre-layout map.
+ * <p>
+ * We might be able to detect the error in the application which will help the developer to
+ * resolve the issue.
+ * <p>
+ * If it is not an expected error, we at least print an error to notify the developer and ignore
+ * the animation.
+ *
+ * https://code.google.com/p/android/issues/detail?id=193958
+ *
+ * @param key The change key
+ * @param holder Current ViewHolder
+ * @param oldChangeViewHolder Changed ViewHolder
+ */
+ private void handleMissingPreInfoForChangeError(long key,
+ ViewHolder holder, ViewHolder oldChangeViewHolder) {
+ // check if two VH have the same key, if so, print that as an error
+ final int childCount = mChildHelper.getChildCount();
+ for (int i = 0; i < childCount; i++) {
+ View view = mChildHelper.getChildAt(i);
+ ViewHolder other = getChildViewHolderInt(view);
+ if (other == holder) {
+ continue;
+ }
+ final long otherKey = getChangedHolderKey(other);
+ if (otherKey == key) {
+ if (mAdapter != null && mAdapter.hasStableIds()) {
+ throw new IllegalStateException("Two different ViewHolders have the same stable"
+ + " ID. Stable IDs in your adapter MUST BE unique and SHOULD NOT"
+ + " change.\n ViewHolder 1:" + other + " \n View Holder 2:" + holder);
+ } else {
+ throw new IllegalStateException("Two different ViewHolders have the same change"
+ + " ID. This might happen due to inconsistent Adapter update events or"
+ + " if the LayoutManager lays out the same View multiple times."
+ + "\n ViewHolder 1:" + other + " \n View Holder 2:" + holder);
+ }
+ }
+ }
+ // Very unlikely to happen but if it does, notify the developer.
+ Log.e(TAG, "Problem while matching changed view holders with the new"
+ + "ones. The pre-layout information for the change holder " + oldChangeViewHolder
+ + " cannot be found but it is necessary for " + holder);
+ }
+
+ /**
+ * Records the animation information for a view holder that was bounced from hidden list. It
+ * also clears the bounce back flag.
+ */
+ void recordAnimationInfoIfBouncedHiddenView(ViewHolder viewHolder,
+ ItemHolderInfo animationInfo) {
+ // looks like this view bounced back from hidden list!
+ viewHolder.setFlags(0, ViewHolder.FLAG_BOUNCED_FROM_HIDDEN_LIST);
+ if (mState.mTrackOldChangeHolders && viewHolder.isUpdated()
+ && !viewHolder.isRemoved() && !viewHolder.shouldIgnore()) {
+ long key = getChangedHolderKey(viewHolder);
+ mViewInfoStore.addToOldChangeHolders(key, viewHolder);
+ }
+ mViewInfoStore.addToPreLayout(viewHolder, animationInfo);
+ }
+
+ private void findMinMaxChildLayoutPositions(int[] into) {
+ final int count = mChildHelper.getChildCount();
+ if (count == 0) {
+ into[0] = NO_POSITION;
+ into[1] = NO_POSITION;
+ return;
+ }
+ int minPositionPreLayout = Integer.MAX_VALUE;
+ int maxPositionPreLayout = Integer.MIN_VALUE;
+ for (int i = 0; i < count; ++i) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getChildAt(i));
+ if (holder.shouldIgnore()) {
+ continue;
+ }
+ final int pos = holder.getLayoutPosition();
+ if (pos < minPositionPreLayout) {
+ minPositionPreLayout = pos;
+ }
+ if (pos > maxPositionPreLayout) {
+ maxPositionPreLayout = pos;
+ }
+ }
+ into[0] = minPositionPreLayout;
+ into[1] = maxPositionPreLayout;
+ }
+
+ private boolean didChildRangeChange(int minPositionPreLayout, int maxPositionPreLayout) {
+ findMinMaxChildLayoutPositions(mMinMaxLayoutPositions);
+ return mMinMaxLayoutPositions[0] != minPositionPreLayout
+ || mMinMaxLayoutPositions[1] != maxPositionPreLayout;
+ }
+
+ @Override
+ protected void removeDetachedView(View child, boolean animate) {
+ ViewHolder vh = getChildViewHolderInt(child);
+ if (vh != null) {
+ if (vh.isTmpDetached()) {
+ vh.clearTmpDetachFlag();
+ } else if (!vh.shouldIgnore()) {
+ throw new IllegalArgumentException("Called removeDetachedView with a view which"
+ + " is not flagged as tmp detached." + vh);
+ }
+ }
+ dispatchChildDetached(child);
+ super.removeDetachedView(child, animate);
+ }
+
+ /**
+ * Returns a unique key to be used while handling change animations.
+ * It might be child's position or stable id depending on the adapter type.
+ */
+ long getChangedHolderKey(ViewHolder holder) {
+ return mAdapter.hasStableIds() ? holder.getItemId() : holder.mPosition;
+ }
+
+ void animateAppearance(@NonNull ViewHolder itemHolder,
+ @Nullable ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo) {
+ itemHolder.setIsRecyclable(false);
+ if (mItemAnimator.animateAppearance(itemHolder, preLayoutInfo, postLayoutInfo)) {
+ postAnimationRunner();
+ }
+ }
+
+ void animateDisappearance(@NonNull ViewHolder holder,
+ @NonNull ItemHolderInfo preLayoutInfo, @Nullable ItemHolderInfo postLayoutInfo) {
+ addAnimatingView(holder);
+ holder.setIsRecyclable(false);
+ if (mItemAnimator.animateDisappearance(holder, preLayoutInfo, postLayoutInfo)) {
+ postAnimationRunner();
+ }
+ }
+
+ private void animateChange(@NonNull ViewHolder oldHolder, @NonNull ViewHolder newHolder,
+ @NonNull ItemHolderInfo preInfo, @NonNull ItemHolderInfo postInfo,
+ boolean oldHolderDisappearing, boolean newHolderDisappearing) {
+ oldHolder.setIsRecyclable(false);
+ if (oldHolderDisappearing) {
+ addAnimatingView(oldHolder);
+ }
+ if (oldHolder != newHolder) {
+ if (newHolderDisappearing) {
+ addAnimatingView(newHolder);
+ }
+ oldHolder.mShadowedHolder = newHolder;
+ // old holder should disappear after animation ends
+ addAnimatingView(oldHolder);
+ mRecycler.unscrapView(oldHolder);
+ newHolder.setIsRecyclable(false);
+ newHolder.mShadowingHolder = oldHolder;
+ }
+ if (mItemAnimator.animateChange(oldHolder, newHolder, preInfo, postInfo)) {
+ postAnimationRunner();
+ }
+ }
+
+ @Override
+ protected void onLayout(boolean changed, int l, int t, int r, int b) {
+ Trace.beginSection(TRACE_ON_LAYOUT_TAG);
+ dispatchLayout();
+ Trace.endSection();
+ mFirstLayoutComplete = true;
+ }
+
+ @Override
+ public void requestLayout() {
+ if (mEatRequestLayout == 0 && !mLayoutFrozen) {
+ super.requestLayout();
+ } else {
+ mLayoutRequestEaten = true;
+ }
+ }
+
+ void markItemDecorInsetsDirty() {
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final View child = mChildHelper.getUnfilteredChildAt(i);
+ ((LayoutParams) child.getLayoutParams()).mInsetsDirty = true;
+ }
+ mRecycler.markItemDecorInsetsDirty();
+ }
+
+ @Override
+ public void draw(Canvas c) {
+ super.draw(c);
+
+ final int count = mItemDecorations.size();
+ for (int i = 0; i < count; i++) {
+ mItemDecorations.get(i).onDrawOver(c, this, mState);
+ }
+ // TODO If padding is not 0 and clipChildrenToPadding is false, to draw glows properly, we
+ // need find children closest to edges. Not sure if it is worth the effort.
+ boolean needsInvalidate = false;
+ if (mLeftGlow != null && !mLeftGlow.isFinished()) {
+ final int restore = c.save();
+ final int padding = mClipToPadding ? getPaddingBottom() : 0;
+ c.rotate(270);
+ c.translate(-getHeight() + padding, 0);
+ needsInvalidate = mLeftGlow != null && mLeftGlow.draw(c);
+ c.restoreToCount(restore);
+ }
+ if (mTopGlow != null && !mTopGlow.isFinished()) {
+ final int restore = c.save();
+ if (mClipToPadding) {
+ c.translate(getPaddingLeft(), getPaddingTop());
+ }
+ needsInvalidate |= mTopGlow != null && mTopGlow.draw(c);
+ c.restoreToCount(restore);
+ }
+ if (mRightGlow != null && !mRightGlow.isFinished()) {
+ final int restore = c.save();
+ final int width = getWidth();
+ final int padding = mClipToPadding ? getPaddingTop() : 0;
+ c.rotate(90);
+ c.translate(-padding, -width);
+ needsInvalidate |= mRightGlow != null && mRightGlow.draw(c);
+ c.restoreToCount(restore);
+ }
+ if (mBottomGlow != null && !mBottomGlow.isFinished()) {
+ final int restore = c.save();
+ c.rotate(180);
+ if (mClipToPadding) {
+ c.translate(-getWidth() + getPaddingRight(), -getHeight() + getPaddingBottom());
+ } else {
+ c.translate(-getWidth(), -getHeight());
+ }
+ needsInvalidate |= mBottomGlow != null && mBottomGlow.draw(c);
+ c.restoreToCount(restore);
+ }
+
+ // If some views are animating, ItemDecorators are likely to move/change with them.
+ // Invalidate RecyclerView to re-draw decorators. This is still efficient because children's
+ // display lists are not invalidated.
+ if (!needsInvalidate && mItemAnimator != null && mItemDecorations.size() > 0
+ && mItemAnimator.isRunning()) {
+ needsInvalidate = true;
+ }
+
+ if (needsInvalidate) {
+ postInvalidateOnAnimation();
+ }
+ }
+
+ @Override
+ public void onDraw(Canvas c) {
+ super.onDraw(c);
+
+ final int count = mItemDecorations.size();
+ for (int i = 0; i < count; i++) {
+ mItemDecorations.get(i).onDraw(c, this, mState);
+ }
+ }
+
+ @Override
+ protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
+ return p instanceof LayoutParams && mLayout.checkLayoutParams((LayoutParams) p);
+ }
+
+ @Override
+ protected ViewGroup.LayoutParams generateDefaultLayoutParams() {
+ if (mLayout == null) {
+ throw new IllegalStateException("RecyclerView has no LayoutManager");
+ }
+ return mLayout.generateDefaultLayoutParams();
+ }
+
+ @Override
+ public ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs) {
+ if (mLayout == null) {
+ throw new IllegalStateException("RecyclerView has no LayoutManager");
+ }
+ return mLayout.generateLayoutParams(getContext(), attrs);
+ }
+
+ @Override
+ protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
+ if (mLayout == null) {
+ throw new IllegalStateException("RecyclerView has no LayoutManager");
+ }
+ return mLayout.generateLayoutParams(p);
+ }
+
+ /**
+ * Returns true if RecyclerView is currently running some animations.
+ * <p>
+ * If you want to be notified when animations are finished, use
+ * {@link ItemAnimator#isRunning(ItemAnimator.ItemAnimatorFinishedListener)}.
+ *
+ * @return True if there are some item animations currently running or waiting to be started.
+ */
+ public boolean isAnimating() {
+ return mItemAnimator != null && mItemAnimator.isRunning();
+ }
+
+ void saveOldPositions() {
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (DEBUG && holder.mPosition == -1 && !holder.isRemoved()) {
+ throw new IllegalStateException("view holder cannot have position -1 unless it"
+ + " is removed");
+ }
+ if (!holder.shouldIgnore()) {
+ holder.saveOldPosition();
+ }
+ }
+ }
+
+ void clearOldPositions() {
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (!holder.shouldIgnore()) {
+ holder.clearOldPosition();
+ }
+ }
+ mRecycler.clearOldPositions();
+ }
+
+ void offsetPositionRecordsForMove(int from, int to) {
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ final int start, end, inBetweenOffset;
+ if (from < to) {
+ start = from;
+ end = to;
+ inBetweenOffset = -1;
+ } else {
+ start = to;
+ end = from;
+ inBetweenOffset = 1;
+ }
+
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (holder == null || holder.mPosition < start || holder.mPosition > end) {
+ continue;
+ }
+ if (DEBUG) {
+ Log.d(TAG, "offsetPositionRecordsForMove attached child " + i + " holder "
+ + holder);
+ }
+ if (holder.mPosition == from) {
+ holder.offsetPosition(to - from, false);
+ } else {
+ holder.offsetPosition(inBetweenOffset, false);
+ }
+
+ mState.mStructureChanged = true;
+ }
+ mRecycler.offsetPositionRecordsForMove(from, to);
+ requestLayout();
+ }
+
+ void offsetPositionRecordsForInsert(int positionStart, int itemCount) {
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (holder != null && !holder.shouldIgnore() && holder.mPosition >= positionStart) {
+ if (DEBUG) {
+ Log.d(TAG, "offsetPositionRecordsForInsert attached child " + i + " holder "
+ + holder + " now at position " + (holder.mPosition + itemCount));
+ }
+ holder.offsetPosition(itemCount, false);
+ mState.mStructureChanged = true;
+ }
+ }
+ mRecycler.offsetPositionRecordsForInsert(positionStart, itemCount);
+ requestLayout();
+ }
+
+ void offsetPositionRecordsForRemove(int positionStart, int itemCount,
+ boolean applyToPreLayout) {
+ final int positionEnd = positionStart + itemCount;
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (holder != null && !holder.shouldIgnore()) {
+ if (holder.mPosition >= positionEnd) {
+ if (DEBUG) {
+ Log.d(TAG, "offsetPositionRecordsForRemove attached child " + i
+ + " holder " + holder + " now at position "
+ + (holder.mPosition - itemCount));
+ }
+ holder.offsetPosition(-itemCount, applyToPreLayout);
+ mState.mStructureChanged = true;
+ } else if (holder.mPosition >= positionStart) {
+ if (DEBUG) {
+ Log.d(TAG, "offsetPositionRecordsForRemove attached child " + i
+ + " holder " + holder + " now REMOVED");
+ }
+ holder.flagRemovedAndOffsetPosition(positionStart - 1, -itemCount,
+ applyToPreLayout);
+ mState.mStructureChanged = true;
+ }
+ }
+ }
+ mRecycler.offsetPositionRecordsForRemove(positionStart, itemCount, applyToPreLayout);
+ requestLayout();
+ }
+
+ /**
+ * Rebind existing views for the given range, or create as needed.
+ *
+ * @param positionStart Adapter position to start at
+ * @param itemCount Number of views that must explicitly be rebound
+ */
+ void viewRangeUpdate(int positionStart, int itemCount, Object payload) {
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ final int positionEnd = positionStart + itemCount;
+
+ for (int i = 0; i < childCount; i++) {
+ final View child = mChildHelper.getUnfilteredChildAt(i);
+ final ViewHolder holder = getChildViewHolderInt(child);
+ if (holder == null || holder.shouldIgnore()) {
+ continue;
+ }
+ if (holder.mPosition >= positionStart && holder.mPosition < positionEnd) {
+ // We re-bind these view holders after pre-processing is complete so that
+ // ViewHolders have their final positions assigned.
+ holder.addFlags(ViewHolder.FLAG_UPDATE);
+ holder.addChangePayload(payload);
+ // lp cannot be null since we get ViewHolder from it.
+ ((LayoutParams) child.getLayoutParams()).mInsetsDirty = true;
+ }
+ }
+ mRecycler.viewRangeUpdate(positionStart, itemCount);
+ }
+
+ boolean canReuseUpdatedViewHolder(ViewHolder viewHolder) {
+ return mItemAnimator == null || mItemAnimator.canReuseUpdatedViewHolder(viewHolder,
+ viewHolder.getUnmodifiedPayloads());
+ }
+
+
+ /**
+ * Call this method to signal that *all* adapter content has changed (generally, because of
+ * swapAdapter, or notifyDataSetChanged), and that once layout occurs, all attached items should
+ * be discarded or animated. Note that this work is deferred because RecyclerView requires a
+ * layout to resolve non-incremental changes to the data set.
+ *
+ * Attached items are labeled as position unknown, and may no longer be cached.
+ *
+ * It is still possible for items to be prefetched while mDataSetHasChangedAfterLayout == true,
+ * so calling this method *must* be associated with marking the cache invalid, so that the
+ * only valid items that remain in the cache, once layout occurs, are prefetched items.
+ */
+ void setDataSetChangedAfterLayout() {
+ if (mDataSetHasChangedAfterLayout) {
+ return;
+ }
+ mDataSetHasChangedAfterLayout = true;
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (holder != null && !holder.shouldIgnore()) {
+ holder.addFlags(ViewHolder.FLAG_ADAPTER_POSITION_UNKNOWN);
+ }
+ }
+ mRecycler.setAdapterPositionsAsUnknown();
+
+ // immediately mark all views as invalid, so prefetched views can be
+ // differentiated from views bound to previous data set - both in children, and cache
+ markKnownViewsInvalid();
+ }
+
+ /**
+ * Mark all known views as invalid. Used in response to a, "the whole world might have changed"
+ * data change event.
+ */
+ void markKnownViewsInvalid() {
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (holder != null && !holder.shouldIgnore()) {
+ holder.addFlags(ViewHolder.FLAG_UPDATE | ViewHolder.FLAG_INVALID);
+ }
+ }
+ markItemDecorInsetsDirty();
+ mRecycler.markKnownViewsInvalid();
+ }
+
+ /**
+ * Invalidates all ItemDecorations. If RecyclerView has item decorations, calling this method
+ * will trigger a {@link #requestLayout()} call.
+ */
+ public void invalidateItemDecorations() {
+ if (mItemDecorations.size() == 0) {
+ return;
+ }
+ if (mLayout != null) {
+ mLayout.assertNotInLayoutOrScroll("Cannot invalidate item decorations during a scroll"
+ + " or layout");
+ }
+ markItemDecorInsetsDirty();
+ requestLayout();
+ }
+
+ /**
+ * Returns true if the RecyclerView should attempt to preserve currently focused Adapter Item's
+ * focus even if the View representing the Item is replaced during a layout calculation.
+ * <p>
+ * By default, this value is {@code true}.
+ *
+ * @return True if the RecyclerView will try to preserve focused Item after a layout if it loses
+ * focus.
+ *
+ * @see #setPreserveFocusAfterLayout(boolean)
+ */
+ public boolean getPreserveFocusAfterLayout() {
+ return mPreserveFocusAfterLayout;
+ }
+
+ /**
+ * Set whether the RecyclerView should try to keep the same Item focused after a layout
+ * calculation or not.
+ * <p>
+ * Usually, LayoutManagers keep focused views visible before and after layout but sometimes,
+ * views may lose focus during a layout calculation as their state changes or they are replaced
+ * with another view due to type change or animation. In these cases, RecyclerView can request
+ * focus on the new view automatically.
+ *
+ * @param preserveFocusAfterLayout Whether RecyclerView should preserve focused Item during a
+ * layout calculations. Defaults to true.
+ *
+ * @see #getPreserveFocusAfterLayout()
+ */
+ public void setPreserveFocusAfterLayout(boolean preserveFocusAfterLayout) {
+ mPreserveFocusAfterLayout = preserveFocusAfterLayout;
+ }
+
+ /**
+ * Retrieve the {@link ViewHolder} for the given child view.
+ *
+ * @param child Child of this RecyclerView to query for its ViewHolder
+ * @return The child view's ViewHolder
+ */
+ public ViewHolder getChildViewHolder(View child) {
+ final ViewParent parent = child.getParent();
+ if (parent != null && parent != this) {
+ throw new IllegalArgumentException("View " + child + " is not a direct child of "
+ + this);
+ }
+ return getChildViewHolderInt(child);
+ }
+
+ /**
+ * Traverses the ancestors of the given view and returns the item view that contains it and
+ * also a direct child of the RecyclerView. This returned view can be used to get the
+ * ViewHolder by calling {@link #getChildViewHolder(View)}.
+ *
+ * @param view The view that is a descendant of the RecyclerView.
+ *
+ * @return The direct child of the RecyclerView which contains the given view or null if the
+ * provided view is not a descendant of this RecyclerView.
+ *
+ * @see #getChildViewHolder(View)
+ * @see #findContainingViewHolder(View)
+ */
+ @Nullable
+ public View findContainingItemView(View view) {
+ ViewParent parent = view.getParent();
+ while (parent != null && parent != this && parent instanceof View) {
+ view = (View) parent;
+ parent = view.getParent();
+ }
+ return parent == this ? view : null;
+ }
+
+ /**
+ * Returns the ViewHolder that contains the given view.
+ *
+ * @param view The view that is a descendant of the RecyclerView.
+ *
+ * @return The ViewHolder that contains the given view or null if the provided view is not a
+ * descendant of this RecyclerView.
+ */
+ @Nullable
+ public ViewHolder findContainingViewHolder(View view) {
+ View itemView = findContainingItemView(view);
+ return itemView == null ? null : getChildViewHolder(itemView);
+ }
+
+
+ static ViewHolder getChildViewHolderInt(View child) {
+ if (child == null) {
+ return null;
+ }
+ return ((LayoutParams) child.getLayoutParams()).mViewHolder;
+ }
+
+ /**
+ * @deprecated use {@link #getChildAdapterPosition(View)} or
+ * {@link #getChildLayoutPosition(View)}.
+ */
+ @Deprecated
+ public int getChildPosition(View child) {
+ return getChildAdapterPosition(child);
+ }
+
+ /**
+ * Return the adapter position that the given child view corresponds to.
+ *
+ * @param child Child View to query
+ * @return Adapter position corresponding to the given view or {@link #NO_POSITION}
+ */
+ public int getChildAdapterPosition(View child) {
+ final ViewHolder holder = getChildViewHolderInt(child);
+ return holder != null ? holder.getAdapterPosition() : NO_POSITION;
+ }
+
+ /**
+ * Return the adapter position of the given child view as of the latest completed layout pass.
+ * <p>
+ * This position may not be equal to Item's adapter position if there are pending changes
+ * in the adapter which have not been reflected to the layout yet.
+ *
+ * @param child Child View to query
+ * @return Adapter position of the given View as of last layout pass or {@link #NO_POSITION} if
+ * the View is representing a removed item.
+ */
+ public int getChildLayoutPosition(View child) {
+ final ViewHolder holder = getChildViewHolderInt(child);
+ return holder != null ? holder.getLayoutPosition() : NO_POSITION;
+ }
+
+ /**
+ * Return the stable item id that the given child view corresponds to.
+ *
+ * @param child Child View to query
+ * @return Item id corresponding to the given view or {@link #NO_ID}
+ */
+ public long getChildItemId(View child) {
+ if (mAdapter == null || !mAdapter.hasStableIds()) {
+ return NO_ID;
+ }
+ final ViewHolder holder = getChildViewHolderInt(child);
+ return holder != null ? holder.getItemId() : NO_ID;
+ }
+
+ /**
+ * @deprecated use {@link #findViewHolderForLayoutPosition(int)} or
+ * {@link #findViewHolderForAdapterPosition(int)}
+ */
+ @Deprecated
+ public ViewHolder findViewHolderForPosition(int position) {
+ return findViewHolderForPosition(position, false);
+ }
+
+ /**
+ * Return the ViewHolder for the item in the given position of the data set as of the latest
+ * layout pass.
+ * <p>
+ * This method checks only the children of RecyclerView. If the item at the given
+ * <code>position</code> is not laid out, it <em>will not</em> create a new one.
+ * <p>
+ * Note that when Adapter contents change, ViewHolder positions are not updated until the
+ * next layout calculation. If there are pending adapter updates, the return value of this
+ * method may not match your adapter contents. You can use
+ * #{@link ViewHolder#getAdapterPosition()} to get the current adapter position of a ViewHolder.
+ * <p>
+ * When the ItemAnimator is running a change animation, there might be 2 ViewHolders
+ * with the same layout position representing the same Item. In this case, the updated
+ * ViewHolder will be returned.
+ *
+ * @param position The position of the item in the data set of the adapter
+ * @return The ViewHolder at <code>position</code> or null if there is no such item
+ */
+ public ViewHolder findViewHolderForLayoutPosition(int position) {
+ return findViewHolderForPosition(position, false);
+ }
+
+ /**
+ * Return the ViewHolder for the item in the given position of the data set. Unlike
+ * {@link #findViewHolderForLayoutPosition(int)} this method takes into account any pending
+ * adapter changes that may not be reflected to the layout yet. On the other hand, if
+ * {@link Adapter#notifyDataSetChanged()} has been called but the new layout has not been
+ * calculated yet, this method will return <code>null</code> since the new positions of views
+ * are unknown until the layout is calculated.
+ * <p>
+ * This method checks only the children of RecyclerView. If the item at the given
+ * <code>position</code> is not laid out, it <em>will not</em> create a new one.
+ * <p>
+ * When the ItemAnimator is running a change animation, there might be 2 ViewHolders
+ * representing the same Item. In this case, the updated ViewHolder will be returned.
+ *
+ * @param position The position of the item in the data set of the adapter
+ * @return The ViewHolder at <code>position</code> or null if there is no such item
+ */
+ public ViewHolder findViewHolderForAdapterPosition(int position) {
+ if (mDataSetHasChangedAfterLayout) {
+ return null;
+ }
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ // hidden VHs are not preferred but if that is the only one we find, we rather return it
+ ViewHolder hidden = null;
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (holder != null && !holder.isRemoved()
+ && getAdapterPositionFor(holder) == position) {
+ if (mChildHelper.isHidden(holder.itemView)) {
+ hidden = holder;
+ } else {
+ return holder;
+ }
+ }
+ }
+ return hidden;
+ }
+
+ ViewHolder findViewHolderForPosition(int position, boolean checkNewPosition) {
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ ViewHolder hidden = null;
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (holder != null && !holder.isRemoved()) {
+ if (checkNewPosition) {
+ if (holder.mPosition != position) {
+ continue;
+ }
+ } else if (holder.getLayoutPosition() != position) {
+ continue;
+ }
+ if (mChildHelper.isHidden(holder.itemView)) {
+ hidden = holder;
+ } else {
+ return holder;
+ }
+ }
+ }
+ // This method should not query cached views. It creates a problem during adapter updates
+ // when we are dealing with already laid out views. Also, for the public method, it is more
+ // reasonable to return null if position is not laid out.
+ return hidden;
+ }
+
+ /**
+ * Return the ViewHolder for the item with the given id. The RecyclerView must
+ * use an Adapter with {@link Adapter#setHasStableIds(boolean) stableIds} to
+ * return a non-null value.
+ * <p>
+ * This method checks only the children of RecyclerView. If the item with the given
+ * <code>id</code> is not laid out, it <em>will not</em> create a new one.
+ *
+ * When the ItemAnimator is running a change animation, there might be 2 ViewHolders with the
+ * same id. In this case, the updated ViewHolder will be returned.
+ *
+ * @param id The id for the requested item
+ * @return The ViewHolder with the given <code>id</code> or null if there is no such item
+ */
+ public ViewHolder findViewHolderForItemId(long id) {
+ if (mAdapter == null || !mAdapter.hasStableIds()) {
+ return null;
+ }
+ final int childCount = mChildHelper.getUnfilteredChildCount();
+ ViewHolder hidden = null;
+ for (int i = 0; i < childCount; i++) {
+ final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
+ if (holder != null && !holder.isRemoved() && holder.getItemId() == id) {
+ if (mChildHelper.isHidden(holder.itemView)) {
+ hidden = holder;
+ } else {
+ return holder;
+ }
+ }
+ }
+ return hidden;
+ }
+
+ /**
+ * Find the topmost view under the given point.
+ *
+ * @param x Horizontal position in pixels to search
+ * @param y Vertical position in pixels to search
+ * @return The child view under (x, y) or null if no matching child is found
+ */
+ public View findChildViewUnder(float x, float y) {
+ final int count = mChildHelper.getChildCount();
+ for (int i = count - 1; i >= 0; i--) {
+ final View child = mChildHelper.getChildAt(i);
+ final float translationX = child.getTranslationX();
+ final float translationY = child.getTranslationY();
+ if (x >= child.getLeft() + translationX
+ && x <= child.getRight() + translationX
+ && y >= child.getTop() + translationY
+ && y <= child.getBottom() + translationY) {
+ return child;
+ }
+ }
+ return null;
+ }
+
+ @Override
+ public boolean drawChild(Canvas canvas, View child, long drawingTime) {
+ return super.drawChild(canvas, child, drawingTime);
+ }
+
+ /**
+ * Offset the bounds of all child views by <code>dy</code> pixels.
+ * Useful for implementing simple scrolling in {@link LayoutManager LayoutManagers}.
+ *
+ * @param dy Vertical pixel offset to apply to the bounds of all child views
+ */
+ public void offsetChildrenVertical(int dy) {
+ final int childCount = mChildHelper.getChildCount();
+ for (int i = 0; i < childCount; i++) {
+ mChildHelper.getChildAt(i).offsetTopAndBottom(dy);
+ }
+ }
+
+ /**
+ * Called when an item view is attached to this RecyclerView.
+ *
+ * <p>Subclasses of RecyclerView may want to perform extra bookkeeping or modifications
+ * of child views as they become attached. This will be called before a
+ * {@link LayoutManager} measures or lays out the view and is a good time to perform these
+ * changes.</p>
+ *
+ * @param child Child view that is now attached to this RecyclerView and its associated window
+ */
+ public void onChildAttachedToWindow(View child) {
+ }
+
+ /**
+ * Called when an item view is detached from this RecyclerView.
+ *
+ * <p>Subclasses of RecyclerView may want to perform extra bookkeeping or modifications
+ * of child views as they become detached. This will be called as a
+ * {@link LayoutManager} fully detaches the child view from the parent and its window.</p>
+ *
+ * @param child Child view that is now detached from this RecyclerView and its associated window
+ */
+ public void onChildDetachedFromWindow(View child) {
+ }
+
+ /**
+ * Offset the bounds of all child views by <code>dx</code> pixels.
+ * Useful for implementing simple scrolling in {@link LayoutManager LayoutManagers}.
+ *
+ * @param dx Horizontal pixel offset to apply to the bounds of all child views
+ */
+ public void offsetChildrenHorizontal(int dx) {
+ final int childCount = mChildHelper.getChildCount();
+ for (int i = 0; i < childCount; i++) {
+ mChildHelper.getChildAt(i).offsetLeftAndRight(dx);
+ }
+ }
+
+ /**
+ * Returns the bounds of the view including its decoration and margins.
+ *
+ * @param view The view element to check
+ * @param outBounds A rect that will receive the bounds of the element including its
+ * decoration and margins.
+ */
+ public void getDecoratedBoundsWithMargins(View view, Rect outBounds) {
+ getDecoratedBoundsWithMarginsInt(view, outBounds);
+ }
+
+ static void getDecoratedBoundsWithMarginsInt(View view, Rect outBounds) {
+ final LayoutParams lp = (LayoutParams) view.getLayoutParams();
+ final Rect insets = lp.mDecorInsets;
+ outBounds.set(view.getLeft() - insets.left - lp.leftMargin,
+ view.getTop() - insets.top - lp.topMargin,
+ view.getRight() + insets.right + lp.rightMargin,
+ view.getBottom() + insets.bottom + lp.bottomMargin);
+ }
+
+ Rect getItemDecorInsetsForChild(View child) {
+ final LayoutParams lp = (LayoutParams) child.getLayoutParams();
+ if (!lp.mInsetsDirty) {
+ return lp.mDecorInsets;
+ }
+
+ if (mState.isPreLayout() && (lp.isItemChanged() || lp.isViewInvalid())) {
+ // changed/invalid items should not be updated until they are rebound.
+ return lp.mDecorInsets;
+ }
+ final Rect insets = lp.mDecorInsets;
+ insets.set(0, 0, 0, 0);
+ final int decorCount = mItemDecorations.size();
+ for (int i = 0; i < decorCount; i++) {
+ mTempRect.set(0, 0, 0, 0);
+ mItemDecorations.get(i).getItemOffsets(mTempRect, child, this, mState);
+ insets.left += mTempRect.left;
+ insets.top += mTempRect.top;
+ insets.right += mTempRect.right;
+ insets.bottom += mTempRect.bottom;
+ }
+ lp.mInsetsDirty = false;
+ return insets;
+ }
+
+ /**
+ * Called when the scroll position of this RecyclerView changes. Subclasses should use
+ * this method to respond to scrolling within the adapter's data set instead of an explicit
+ * listener.
+ *
+ * <p>This method will always be invoked before listeners. If a subclass needs to perform
+ * any additional upkeep or bookkeeping after scrolling but before listeners run,
+ * this is a good place to do so.</p>
+ *
+ * <p>This differs from {@link View#onScrollChanged(int, int, int, int)} in that it receives
+ * the distance scrolled in either direction within the adapter's data set instead of absolute
+ * scroll coordinates. Since RecyclerView cannot compute the absolute scroll position from
+ * any arbitrary point in the data set, <code>onScrollChanged</code> will always receive
+ * the current {@link View#getScrollX()} and {@link View#getScrollY()} values which
+ * do not correspond to the data set scroll position. However, some subclasses may choose
+ * to use these fields as special offsets.</p>
+ *
+ * @param dx horizontal distance scrolled in pixels
+ * @param dy vertical distance scrolled in pixels
+ */
+ public void onScrolled(int dx, int dy) {
+ // Do nothing
+ }
+
+ void dispatchOnScrolled(int hresult, int vresult) {
+ mDispatchScrollCounter++;
+ // Pass the current scrollX/scrollY values; no actual change in these properties occurred
+ // but some general-purpose code may choose to respond to changes this way.
+ final int scrollX = getScrollX();
+ final int scrollY = getScrollY();
+ onScrollChanged(scrollX, scrollY, scrollX, scrollY);
+
+ // Pass the real deltas to onScrolled, the RecyclerView-specific method.
+ onScrolled(hresult, vresult);
+
+ // Invoke listeners last. Subclassed view methods always handle the event first.
+ // All internal state is consistent by the time listeners are invoked.
+ if (mScrollListener != null) {
+ mScrollListener.onScrolled(this, hresult, vresult);
+ }
+ if (mScrollListeners != null) {
+ for (int i = mScrollListeners.size() - 1; i >= 0; i--) {
+ mScrollListeners.get(i).onScrolled(this, hresult, vresult);
+ }
+ }
+ mDispatchScrollCounter--;
+ }
+
+ /**
+ * Called when the scroll state of this RecyclerView changes. Subclasses should use this
+ * method to respond to state changes instead of an explicit listener.
+ *
+ * <p>This method will always be invoked before listeners, but after the LayoutManager
+ * responds to the scroll state change.</p>
+ *
+ * @param state the new scroll state, one of {@link #SCROLL_STATE_IDLE},
+ * {@link #SCROLL_STATE_DRAGGING} or {@link #SCROLL_STATE_SETTLING}
+ */
+ public void onScrollStateChanged(int state) {
+ // Do nothing
+ }
+
+ void dispatchOnScrollStateChanged(int state) {
+ // Let the LayoutManager go first; this allows it to bring any properties into
+ // a consistent state before the RecyclerView subclass responds.
+ if (mLayout != null) {
+ mLayout.onScrollStateChanged(state);
+ }
+
+ // Let the RecyclerView subclass handle this event next; any LayoutManager property
+ // changes will be reflected by this time.
+ onScrollStateChanged(state);
+
+ // Listeners go last. All other internal state is consistent by this point.
+ if (mScrollListener != null) {
+ mScrollListener.onScrollStateChanged(this, state);
+ }
+ if (mScrollListeners != null) {
+ for (int i = mScrollListeners.size() - 1; i >= 0; i--) {
+ mScrollListeners.get(i).onScrollStateChanged(this, state);
+ }
+ }
+ }
+
+ /**
+ * Returns whether there are pending adapter updates which are not yet applied to the layout.
+ * <p>
+ * If this method returns <code>true</code>, it means that what user is currently seeing may not
+ * reflect them adapter contents (depending on what has changed).
+ * You may use this information to defer or cancel some operations.
+ * <p>
+ * This method returns true if RecyclerView has not yet calculated the first layout after it is
+ * attached to the Window or the Adapter has been replaced.
+ *
+ * @return True if there are some adapter updates which are not yet reflected to layout or false
+ * if layout is up to date.
+ */
+ public boolean hasPendingAdapterUpdates() {
+ return !mFirstLayoutComplete || mDataSetHasChangedAfterLayout
+ || mAdapterHelper.hasPendingUpdates();
+ }
+
+ class ViewFlinger implements Runnable {
+ private int mLastFlingX;
+ private int mLastFlingY;
+ private OverScroller mScroller;
+ Interpolator mInterpolator = sQuinticInterpolator;
+
+
+ // When set to true, postOnAnimation callbacks are delayed until the run method completes
+ private boolean mEatRunOnAnimationRequest = false;
+
+ // Tracks if postAnimationCallback should be re-attached when it is done
+ private boolean mReSchedulePostAnimationCallback = false;
+
+ ViewFlinger() {
+ mScroller = new OverScroller(getContext(), sQuinticInterpolator);
+ }
+
+ @Override
+ public void run() {
+ if (mLayout == null) {
+ stop();
+ return; // no layout, cannot scroll.
+ }
+ disableRunOnAnimationRequests();
+ consumePendingUpdateOperations();
+ // keep a local reference so that if it is changed during onAnimation method, it won't
+ // cause unexpected behaviors
+ final OverScroller scroller = mScroller;
+ final SmoothScroller smoothScroller = mLayout.mSmoothScroller;
+ if (scroller.computeScrollOffset()) {
+ final int x = scroller.getCurrX();
+ final int y = scroller.getCurrY();
+ final int dx = x - mLastFlingX;
+ final int dy = y - mLastFlingY;
+ int hresult = 0;
+ int vresult = 0;
+ mLastFlingX = x;
+ mLastFlingY = y;
+ int overscrollX = 0, overscrollY = 0;
+ if (mAdapter != null) {
+ eatRequestLayout();
+ onEnterLayoutOrScroll();
+ Trace.beginSection(TRACE_SCROLL_TAG);
+ if (dx != 0) {
+ hresult = mLayout.scrollHorizontallyBy(dx, mRecycler, mState);
+ overscrollX = dx - hresult;
+ }
+ if (dy != 0) {
+ vresult = mLayout.scrollVerticallyBy(dy, mRecycler, mState);
+ overscrollY = dy - vresult;
+ }
+ Trace.endSection();
+ repositionShadowingViews();
+
+ onExitLayoutOrScroll();
+ resumeRequestLayout(false);
+
+ if (smoothScroller != null && !smoothScroller.isPendingInitialRun()
+ && smoothScroller.isRunning()) {
+ final int adapterSize = mState.getItemCount();
+ if (adapterSize == 0) {
+ smoothScroller.stop();
+ } else if (smoothScroller.getTargetPosition() >= adapterSize) {
+ smoothScroller.setTargetPosition(adapterSize - 1);
+ smoothScroller.onAnimation(dx - overscrollX, dy - overscrollY);
+ } else {
+ smoothScroller.onAnimation(dx - overscrollX, dy - overscrollY);
+ }
+ }
+ }
+ if (!mItemDecorations.isEmpty()) {
+ invalidate();
+ }
+ if (getOverScrollMode() != View.OVER_SCROLL_NEVER) {
+ considerReleasingGlowsOnScroll(dx, dy);
+ }
+ if (overscrollX != 0 || overscrollY != 0) {
+ final int vel = (int) scroller.getCurrVelocity();
+
+ int velX = 0;
+ if (overscrollX != x) {
+ velX = overscrollX < 0 ? -vel : overscrollX > 0 ? vel : 0;
+ }
+
+ int velY = 0;
+ if (overscrollY != y) {
+ velY = overscrollY < 0 ? -vel : overscrollY > 0 ? vel : 0;
+ }
+
+ if (getOverScrollMode() != View.OVER_SCROLL_NEVER) {
+ absorbGlows(velX, velY);
+ }
+ if ((velX != 0 || overscrollX == x || scroller.getFinalX() == 0)
+ && (velY != 0 || overscrollY == y || scroller.getFinalY() == 0)) {
+ scroller.abortAnimation();
+ }
+ }
+ if (hresult != 0 || vresult != 0) {
+ dispatchOnScrolled(hresult, vresult);
+ }
+
+ if (!awakenScrollBars()) {
+ invalidate();
+ }
+
+ final boolean fullyConsumedVertical = dy != 0 && mLayout.canScrollVertically()
+ && vresult == dy;
+ final boolean fullyConsumedHorizontal = dx != 0 && mLayout.canScrollHorizontally()
+ && hresult == dx;
+ final boolean fullyConsumedAny = (dx == 0 && dy == 0) || fullyConsumedHorizontal
+ || fullyConsumedVertical;
+
+ if (scroller.isFinished() || !fullyConsumedAny) {
+ setScrollState(SCROLL_STATE_IDLE); // setting state to idle will stop this.
+ if (ALLOW_THREAD_GAP_WORK) {
+ mPrefetchRegistry.clearPrefetchPositions();
+ }
+ } else {
+ postOnAnimation();
+ if (mGapWorker != null) {
+ mGapWorker.postFromTraversal(RecyclerView.this, dx, dy);
+ }
+ }
+ }
+ // call this after the onAnimation is complete not to have inconsistent callbacks etc.
+ if (smoothScroller != null) {
+ if (smoothScroller.isPendingInitialRun()) {
+ smoothScroller.onAnimation(0, 0);
+ }
+ if (!mReSchedulePostAnimationCallback) {
+ smoothScroller.stop(); //stop if it does not trigger any scroll
+ }
+ }
+ enableRunOnAnimationRequests();
+ }
+
+ private void disableRunOnAnimationRequests() {
+ mReSchedulePostAnimationCallback = false;
+ mEatRunOnAnimationRequest = true;
+ }
+
+ private void enableRunOnAnimationRequests() {
+ mEatRunOnAnimationRequest = false;
+ if (mReSchedulePostAnimationCallback) {
+ postOnAnimation();
+ }
+ }
+
+ void postOnAnimation() {
+ if (mEatRunOnAnimationRequest) {
+ mReSchedulePostAnimationCallback = true;
+ } else {
+ removeCallbacks(this);
+ RecyclerView.this.postOnAnimation(this);
+ }
+ }
+
+ public void fling(int velocityX, int velocityY) {
+ setScrollState(SCROLL_STATE_SETTLING);
+ mLastFlingX = mLastFlingY = 0;
+ mScroller.fling(0, 0, velocityX, velocityY,
+ Integer.MIN_VALUE, Integer.MAX_VALUE, Integer.MIN_VALUE, Integer.MAX_VALUE);
+ postOnAnimation();
+ }
+
+ public void smoothScrollBy(int dx, int dy) {
+ smoothScrollBy(dx, dy, 0, 0);
+ }
+
+ public void smoothScrollBy(int dx, int dy, int vx, int vy) {
+ smoothScrollBy(dx, dy, computeScrollDuration(dx, dy, vx, vy));
+ }
+
+ private float distanceInfluenceForSnapDuration(float f) {
+ f -= 0.5f; // center the values about 0.
+ f *= 0.3f * Math.PI / 2.0f;
+ return (float) Math.sin(f);
+ }
+
+ private int computeScrollDuration(int dx, int dy, int vx, int vy) {
+ final int absDx = Math.abs(dx);
+ final int absDy = Math.abs(dy);
+ final boolean horizontal = absDx > absDy;
+ final int velocity = (int) Math.sqrt(vx * vx + vy * vy);
+ final int delta = (int) Math.sqrt(dx * dx + dy * dy);
+ final int containerSize = horizontal ? getWidth() : getHeight();
+ final int halfContainerSize = containerSize / 2;
+ final float distanceRatio = Math.min(1.f, 1.f * delta / containerSize);
+ final float distance = halfContainerSize + halfContainerSize
+ * distanceInfluenceForSnapDuration(distanceRatio);
+
+ final int duration;
+ if (velocity > 0) {
+ duration = 4 * Math.round(1000 * Math.abs(distance / velocity));
+ } else {
+ float absDelta = (float) (horizontal ? absDx : absDy);
+ duration = (int) (((absDelta / containerSize) + 1) * 300);
+ }
+ return Math.min(duration, MAX_SCROLL_DURATION);
+ }
+
+ public void smoothScrollBy(int dx, int dy, int duration) {
+ smoothScrollBy(dx, dy, duration, sQuinticInterpolator);
+ }
+
+ public void smoothScrollBy(int dx, int dy, Interpolator interpolator) {
+ smoothScrollBy(dx, dy, computeScrollDuration(dx, dy, 0, 0),
+ interpolator == null ? sQuinticInterpolator : interpolator);
+ }
+
+ public void smoothScrollBy(int dx, int dy, int duration, Interpolator interpolator) {
+ if (mInterpolator != interpolator) {
+ mInterpolator = interpolator;
+ mScroller = new OverScroller(getContext(), interpolator);
+ }
+ setScrollState(SCROLL_STATE_SETTLING);
+ mLastFlingX = mLastFlingY = 0;
+ mScroller.startScroll(0, 0, dx, dy, duration);
+ postOnAnimation();
+ }
+
+ public void stop() {
+ removeCallbacks(this);
+ mScroller.abortAnimation();
+ }
+
+ }
+
+ void repositionShadowingViews() {
+ // Fix up shadow views used by change animations
+ int count = mChildHelper.getChildCount();
+ for (int i = 0; i < count; i++) {
+ View view = mChildHelper.getChildAt(i);
+ ViewHolder holder = getChildViewHolder(view);
+ if (holder != null && holder.mShadowingHolder != null) {
+ View shadowingView = holder.mShadowingHolder.itemView;
+ int left = view.getLeft();
+ int top = view.getTop();
+ if (left != shadowingView.getLeft() || top != shadowingView.getTop()) {
+ shadowingView.layout(left, top,
+ left + shadowingView.getWidth(),
+ top + shadowingView.getHeight());
+ }
+ }
+ }
+ }
+
+ private class RecyclerViewDataObserver extends AdapterDataObserver {
+ RecyclerViewDataObserver() {
+ }
+
+ @Override
+ public void onChanged() {
+ assertNotInLayoutOrScroll(null);
+ mState.mStructureChanged = true;
+
+ setDataSetChangedAfterLayout();
+ if (!mAdapterHelper.hasPendingUpdates()) {
+ requestLayout();
+ }
+ }
+
+ @Override
+ public void onItemRangeChanged(int positionStart, int itemCount, Object payload) {
+ assertNotInLayoutOrScroll(null);
+ if (mAdapterHelper.onItemRangeChanged(positionStart, itemCount, payload)) {
+ triggerUpdateProcessor();
+ }
+ }
+
+ @Override
+ public void onItemRangeInserted(int positionStart, int itemCount) {
+ assertNotInLayoutOrScroll(null);
+ if (mAdapterHelper.onItemRangeInserted(positionStart, itemCount)) {
+ triggerUpdateProcessor();
+ }
+ }
+
+ @Override
+ public void onItemRangeRemoved(int positionStart, int itemCount) {
+ assertNotInLayoutOrScroll(null);
+ if (mAdapterHelper.onItemRangeRemoved(positionStart, itemCount)) {
+ triggerUpdateProcessor();
+ }
+ }
+
+ @Override
+ public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
+ assertNotInLayoutOrScroll(null);
+ if (mAdapterHelper.onItemRangeMoved(fromPosition, toPosition, itemCount)) {
+ triggerUpdateProcessor();
+ }
+ }
+
+ void triggerUpdateProcessor() {
+ if (POST_UPDATES_ON_ANIMATION && mHasFixedSize && mIsAttached) {
+ RecyclerView.this.postOnAnimation(mUpdateChildViewsRunnable);
+ } else {
+ mAdapterUpdateDuringMeasure = true;
+ requestLayout();
+ }
+ }
+ }
+
+ /**
+ * RecycledViewPool lets you share Views between multiple RecyclerViews.
+ * <p>
+ * If you want to recycle views across RecyclerViews, create an instance of RecycledViewPool
+ * and use {@link RecyclerView#setRecycledViewPool(RecycledViewPool)}.
+ * <p>
+ * RecyclerView automatically creates a pool for itself if you don't provide one.
+ *
+ */
+ public static class RecycledViewPool {
+ private static final int DEFAULT_MAX_SCRAP = 5;
+
+ /**
+ * Tracks both pooled holders, as well as create/bind timing metadata for the given type.
+ *
+ * Note that this tracks running averages of create/bind time across all RecyclerViews
+ * (and, indirectly, Adapters) that use this pool.
+ *
+ * 1) This enables us to track average create and bind times across multiple adapters. Even
+ * though create (and especially bind) may behave differently for different Adapter
+ * subclasses, sharing the pool is a strong signal that they'll perform similarly, per type.
+ *
+ * 2) If {@link #willBindInTime(int, long, long)} returns false for one view, it will return
+ * false for all other views of its type for the same deadline. This prevents items
+ * constructed by {@link GapWorker} prefetch from being bound to a lower priority prefetch.
+ */
+ static class ScrapData {
+ ArrayList<ViewHolder> mScrapHeap = new ArrayList<>();
+ int mMaxScrap = DEFAULT_MAX_SCRAP;
+ long mCreateRunningAverageNs = 0;
+ long mBindRunningAverageNs = 0;
+ }
+ SparseArray<ScrapData> mScrap = new SparseArray<>();
+
+ private int mAttachCount = 0;
+
+ public void clear() {
+ for (int i = 0; i < mScrap.size(); i++) {
+ ScrapData data = mScrap.valueAt(i);
+ data.mScrapHeap.clear();
+ }
+ }
+
+ public void setMaxRecycledViews(int viewType, int max) {
+ ScrapData scrapData = getScrapDataForType(viewType);
+ scrapData.mMaxScrap = max;
+ final ArrayList<ViewHolder> scrapHeap = scrapData.mScrapHeap;
+ if (scrapHeap != null) {
+ while (scrapHeap.size() > max) {
+ scrapHeap.remove(scrapHeap.size() - 1);
+ }
+ }
+ }
+
+ /**
+ * Returns the current number of Views held by the RecycledViewPool of the given view type.
+ */
+ public int getRecycledViewCount(int viewType) {
+ return getScrapDataForType(viewType).mScrapHeap.size();
+ }
+
+ public ViewHolder getRecycledView(int viewType) {
+ final ScrapData scrapData = mScrap.get(viewType);
+ if (scrapData != null && !scrapData.mScrapHeap.isEmpty()) {
+ final ArrayList<ViewHolder> scrapHeap = scrapData.mScrapHeap;
+ return scrapHeap.remove(scrapHeap.size() - 1);
+ }
+ return null;
+ }
+
+ int size() {
+ int count = 0;
+ for (int i = 0; i < mScrap.size(); i++) {
+ ArrayList<ViewHolder> viewHolders = mScrap.valueAt(i).mScrapHeap;
+ if (viewHolders != null) {
+ count += viewHolders.size();
+ }
+ }
+ return count;
+ }
+
+ public void putRecycledView(ViewHolder scrap) {
+ final int viewType = scrap.getItemViewType();
+ final ArrayList scrapHeap = getScrapDataForType(viewType).mScrapHeap;
+ if (mScrap.get(viewType).mMaxScrap <= scrapHeap.size()) {
+ return;
+ }
+ if (DEBUG && scrapHeap.contains(scrap)) {
+ throw new IllegalArgumentException("this scrap item already exists");
+ }
+ scrap.resetInternal();
+ scrapHeap.add(scrap);
+ }
+
+ long runningAverage(long oldAverage, long newValue) {
+ if (oldAverage == 0) {
+ return newValue;
+ }
+ return (oldAverage / 4 * 3) + (newValue / 4);
+ }
+
+ void factorInCreateTime(int viewType, long createTimeNs) {
+ ScrapData scrapData = getScrapDataForType(viewType);
+ scrapData.mCreateRunningAverageNs = runningAverage(
+ scrapData.mCreateRunningAverageNs, createTimeNs);
+ }
+
+ void factorInBindTime(int viewType, long bindTimeNs) {
+ ScrapData scrapData = getScrapDataForType(viewType);
+ scrapData.mBindRunningAverageNs = runningAverage(
+ scrapData.mBindRunningAverageNs, bindTimeNs);
+ }
+
+ boolean willCreateInTime(int viewType, long approxCurrentNs, long deadlineNs) {
+ long expectedDurationNs = getScrapDataForType(viewType).mCreateRunningAverageNs;
+ return expectedDurationNs == 0 || (approxCurrentNs + expectedDurationNs < deadlineNs);
+ }
+
+ boolean willBindInTime(int viewType, long approxCurrentNs, long deadlineNs) {
+ long expectedDurationNs = getScrapDataForType(viewType).mBindRunningAverageNs;
+ return expectedDurationNs == 0 || (approxCurrentNs + expectedDurationNs < deadlineNs);
+ }
+
+ void attach(Adapter adapter) {
+ mAttachCount++;
+ }
+
+ void detach() {
+ mAttachCount--;
+ }
+
+
+ /**
+ * Detaches the old adapter and attaches the new one.
+ * <p>
+ * RecycledViewPool will clear its cache if it has only one adapter attached and the new
+ * adapter uses a different ViewHolder than the oldAdapter.
+ *
+ * @param oldAdapter The previous adapter instance. Will be detached.
+ * @param newAdapter The new adapter instance. Will be attached.
+ * @param compatibleWithPrevious True if both oldAdapter and newAdapter are using the same
+ * ViewHolder and view types.
+ */
+ void onAdapterChanged(Adapter oldAdapter, Adapter newAdapter,
+ boolean compatibleWithPrevious) {
+ if (oldAdapter != null) {
+ detach();
+ }
+ if (!compatibleWithPrevious && mAttachCount == 0) {
+ clear();
+ }
+ if (newAdapter != null) {
+ attach(newAdapter);
+ }
+ }
+
+ private ScrapData getScrapDataForType(int viewType) {
+ ScrapData scrapData = mScrap.get(viewType);
+ if (scrapData == null) {
+ scrapData = new ScrapData();
+ mScrap.put(viewType, scrapData);
+ }
+ return scrapData;
+ }
+ }
+
+ /**
+ * Utility method for finding an internal RecyclerView, if present
+ */
+ @Nullable
+ static RecyclerView findNestedRecyclerView(@NonNull View view) {
+ if (!(view instanceof ViewGroup)) {
+ return null;
+ }
+ if (view instanceof RecyclerView) {
+ return (RecyclerView) view;
+ }
+ final ViewGroup parent = (ViewGroup) view;
+ final int count = parent.getChildCount();
+ for (int i = 0; i < count; i++) {
+ final View child = parent.getChildAt(i);
+ final RecyclerView descendant = findNestedRecyclerView(child);
+ if (descendant != null) {
+ return descendant;
+ }
+ }
+ return null;
+ }
+
+ /**
+ * Utility method for clearing holder's internal RecyclerView, if present
+ */
+ static void clearNestedRecyclerViewIfNotNested(@NonNull ViewHolder holder) {
+ if (holder.mNestedRecyclerView != null) {
+ View item = holder.mNestedRecyclerView.get();
+ while (item != null) {
+ if (item == holder.itemView) {
+ return; // match found, don't need to clear
+ }
+
+ ViewParent parent = item.getParent();
+ if (parent instanceof View) {
+ item = (View) parent;
+ } else {
+ item = null;
+ }
+ }
+ holder.mNestedRecyclerView = null; // not nested
+ }
+ }
+
+ /**
+ * Time base for deadline-aware work scheduling. Overridable for testing.
+ *
+ * Will return 0 to avoid cost of System.nanoTime where deadline-aware work scheduling
+ * isn't relevant.
+ */
+ long getNanoTime() {
+ if (ALLOW_THREAD_GAP_WORK) {
+ return System.nanoTime();
+ } else {
+ return 0;
+ }
+ }
+
+ /**
+ * A Recycler is responsible for managing scrapped or detached item views for reuse.
+ *
+ * <p>A "scrapped" view is a view that is still attached to its parent RecyclerView but
+ * that has been marked for removal or reuse.</p>
+ *
+ * <p>Typical use of a Recycler by a {@link LayoutManager} will be to obtain views for
+ * an adapter's data set representing the data at a given position or item ID.
+ * If the view to be reused is considered "dirty" the adapter will be asked to rebind it.
+ * If not, the view can be quickly reused by the LayoutManager with no further work.
+ * Clean views that have not {@link android.view.View#isLayoutRequested() requested layout}
+ * may be repositioned by a LayoutManager without remeasurement.</p>
+ */
+ public final class Recycler {
+ final ArrayList<ViewHolder> mAttachedScrap = new ArrayList<>();
+ ArrayList<ViewHolder> mChangedScrap = null;
+
+ final ArrayList<ViewHolder> mCachedViews = new ArrayList<ViewHolder>();
+
+ private final List<ViewHolder>
+ mUnmodifiableAttachedScrap = Collections.unmodifiableList(mAttachedScrap);
+
+ private int mRequestedCacheMax = DEFAULT_CACHE_SIZE;
+ int mViewCacheMax = DEFAULT_CACHE_SIZE;
+
+ RecycledViewPool mRecyclerPool;
+
+ private ViewCacheExtension mViewCacheExtension;
+
+ static final int DEFAULT_CACHE_SIZE = 2;
+
+ /**
+ * Clear scrap views out of this recycler. Detached views contained within a
+ * recycled view pool will remain.
+ */
+ public void clear() {
+ mAttachedScrap.clear();
+ recycleAndClearCachedViews();
+ }
+
+ /**
+ * Set the maximum number of detached, valid views we should retain for later use.
+ *
+ * @param viewCount Number of views to keep before sending views to the shared pool
+ */
+ public void setViewCacheSize(int viewCount) {
+ mRequestedCacheMax = viewCount;
+ updateViewCacheSize();
+ }
+
+ void updateViewCacheSize() {
+ int extraCache = mLayout != null ? mLayout.mPrefetchMaxCountObserved : 0;
+ mViewCacheMax = mRequestedCacheMax + extraCache;
+
+ // first, try the views that can be recycled
+ for (int i = mCachedViews.size() - 1;
+ i >= 0 && mCachedViews.size() > mViewCacheMax; i--) {
+ recycleCachedViewAt(i);
+ }
+ }
+
+ /**
+ * Returns an unmodifiable list of ViewHolders that are currently in the scrap list.
+ *
+ * @return List of ViewHolders in the scrap list.
+ */
+ public List<ViewHolder> getScrapList() {
+ return mUnmodifiableAttachedScrap;
+ }
+
+ /**
+ * Helper method for getViewForPosition.
+ * <p>
+ * Checks whether a given view holder can be used for the provided position.
+ *
+ * @param holder ViewHolder
+ * @return true if ViewHolder matches the provided position, false otherwise
+ */
+ boolean validateViewHolderForOffsetPosition(ViewHolder holder) {
+ // if it is a removed holder, nothing to verify since we cannot ask adapter anymore
+ // if it is not removed, verify the type and id.
+ if (holder.isRemoved()) {
+ if (DEBUG && !mState.isPreLayout()) {
+ throw new IllegalStateException("should not receive a removed view unless it"
+ + " is pre layout");
+ }
+ return mState.isPreLayout();
+ }
+ if (holder.mPosition < 0 || holder.mPosition >= mAdapter.getItemCount()) {
+ throw new IndexOutOfBoundsException("Inconsistency detected. Invalid view holder "
+ + "adapter position" + holder);
+ }
+ if (!mState.isPreLayout()) {
+ // don't check type if it is pre-layout.
+ final int type = mAdapter.getItemViewType(holder.mPosition);
+ if (type != holder.getItemViewType()) {
+ return false;
+ }
+ }
+ if (mAdapter.hasStableIds()) {
+ return holder.getItemId() == mAdapter.getItemId(holder.mPosition);
+ }
+ return true;
+ }
+
+ /**
+ * Attempts to bind view, and account for relevant timing information. If
+ * deadlineNs != FOREVER_NS, this method may fail to bind, and return false.
+ *
+ * @param holder Holder to be bound.
+ * @param offsetPosition Position of item to be bound.
+ * @param position Pre-layout position of item to be bound.
+ * @param deadlineNs Time, relative to getNanoTime(), by which bind/create work should
+ * complete. If FOREVER_NS is passed, this method will not fail to
+ * bind the holder.
+ * @return
+ */
+ private boolean tryBindViewHolderByDeadline(ViewHolder holder, int offsetPosition,
+ int position, long deadlineNs) {
+ holder.mOwnerRecyclerView = RecyclerView.this;
+ final int viewType = holder.getItemViewType();
+ long startBindNs = getNanoTime();
+ if (deadlineNs != FOREVER_NS
+ && !mRecyclerPool.willBindInTime(viewType, startBindNs, deadlineNs)) {
+ // abort - we have a deadline we can't meet
+ return false;
+ }
+ mAdapter.bindViewHolder(holder, offsetPosition);
+ long endBindNs = getNanoTime();
+ mRecyclerPool.factorInBindTime(holder.getItemViewType(), endBindNs - startBindNs);
+ attachAccessibilityDelegate(holder.itemView);
+ if (mState.isPreLayout()) {
+ holder.mPreLayoutPosition = position;
+ }
+ return true;
+ }
+
+ /**
+ * Binds the given View to the position. The View can be a View previously retrieved via
+ * {@link #getViewForPosition(int)} or created by
+ * {@link Adapter#onCreateViewHolder(ViewGroup, int)}.
+ * <p>
+ * Generally, a LayoutManager should acquire its views via {@link #getViewForPosition(int)}
+ * and let the RecyclerView handle caching. This is a helper method for LayoutManager who
+ * wants to handle its own recycling logic.
+ * <p>
+ * Note that, {@link #getViewForPosition(int)} already binds the View to the position so
+ * you don't need to call this method unless you want to bind this View to another position.
+ *
+ * @param view The view to update.
+ * @param position The position of the item to bind to this View.
+ */
+ public void bindViewToPosition(View view, int position) {
+ ViewHolder holder = getChildViewHolderInt(view);
+ if (holder == null) {
+ throw new IllegalArgumentException("The view does not have a ViewHolder. You cannot"
+ + " pass arbitrary views to this method, they should be created by the "
+ + "Adapter");
+ }
+ final int offsetPosition = mAdapterHelper.findPositionOffset(position);
+ if (offsetPosition < 0 || offsetPosition >= mAdapter.getItemCount()) {
+ throw new IndexOutOfBoundsException("Inconsistency detected. Invalid item "
+ + "position " + position + "(offset:" + offsetPosition + ")."
+ + "state:" + mState.getItemCount());
+ }
+ tryBindViewHolderByDeadline(holder, offsetPosition, position, FOREVER_NS);
+
+ final ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();
+ final LayoutParams rvLayoutParams;
+ if (lp == null) {
+ rvLayoutParams = (LayoutParams) generateDefaultLayoutParams();
+ holder.itemView.setLayoutParams(rvLayoutParams);
+ } else if (!checkLayoutParams(lp)) {
+ rvLayoutParams = (LayoutParams) generateLayoutParams(lp);
+ holder.itemView.setLayoutParams(rvLayoutParams);
+ } else {
+ rvLayoutParams = (LayoutParams) lp;
+ }
+
+ rvLayoutParams.mInsetsDirty = true;
+ rvLayoutParams.mViewHolder = holder;
+ rvLayoutParams.mPendingInvalidate = holder.itemView.getParent() == null;
+ }
+
+ /**
+ * RecyclerView provides artificial position range (item count) in pre-layout state and
+ * automatically maps these positions to {@link Adapter} positions when
+ * {@link #getViewForPosition(int)} or {@link #bindViewToPosition(View, int)} is called.
+ * <p>
+ * Usually, LayoutManager does not need to worry about this. However, in some cases, your
+ * LayoutManager may need to call some custom component with item positions in which
+ * case you need the actual adapter position instead of the pre layout position. You
+ * can use this method to convert a pre-layout position to adapter (post layout) position.
+ * <p>
+ * Note that if the provided position belongs to a deleted ViewHolder, this method will
+ * return -1.
+ * <p>
+ * Calling this method in post-layout state returns the same value back.
+ *
+ * @param position The pre-layout position to convert. Must be greater or equal to 0 and
+ * less than {@link State#getItemCount()}.
+ */
+ public int convertPreLayoutPositionToPostLayout(int position) {
+ if (position < 0 || position >= mState.getItemCount()) {
+ throw new IndexOutOfBoundsException("invalid position " + position + ". State "
+ + "item count is " + mState.getItemCount());
+ }
+ if (!mState.isPreLayout()) {
+ return position;
+ }
+ return mAdapterHelper.findPositionOffset(position);
+ }
+
+ /**
+ * Obtain a view initialized for the given position.
+ *
+ * This method should be used by {@link LayoutManager} implementations to obtain
+ * views to represent data from an {@link Adapter}.
+ * <p>
+ * The Recycler may reuse a scrap or detached view from a shared pool if one is
+ * available for the correct view type. If the adapter has not indicated that the
+ * data at the given position has changed, the Recycler will attempt to hand back
+ * a scrap view that was previously initialized for that data without rebinding.
+ *
+ * @param position Position to obtain a view for
+ * @return A view representing the data at <code>position</code> from <code>adapter</code>
+ */
+ public View getViewForPosition(int position) {
+ return getViewForPosition(position, false);
+ }
+
+ View getViewForPosition(int position, boolean dryRun) {
+ return tryGetViewHolderForPositionByDeadline(position, dryRun, FOREVER_NS).itemView;
+ }
+
+ /**
+ * Attempts to get the ViewHolder for the given position, either from the Recycler scrap,
+ * cache, the RecycledViewPool, or creating it directly.
+ * <p>
+ * If a deadlineNs other than {@link #FOREVER_NS} is passed, this method early return
+ * rather than constructing or binding a ViewHolder if it doesn't think it has time.
+ * If a ViewHolder must be constructed and not enough time remains, null is returned. If a
+ * ViewHolder is aquired and must be bound but not enough time remains, an unbound holder is
+ * returned. Use {@link ViewHolder#isBound()} on the returned object to check for this.
+ *
+ * @param position Position of ViewHolder to be returned.
+ * @param dryRun True if the ViewHolder should not be removed from scrap/cache/
+ * @param deadlineNs Time, relative to getNanoTime(), by which bind/create work should
+ * complete. If FOREVER_NS is passed, this method will not fail to
+ * create/bind the holder if needed.
+ *
+ * @return ViewHolder for requested position
+ */
+ @Nullable
+ ViewHolder tryGetViewHolderForPositionByDeadline(int position,
+ boolean dryRun, long deadlineNs) {
+ if (position < 0 || position >= mState.getItemCount()) {
+ throw new IndexOutOfBoundsException("Invalid item position " + position
+ + "(" + position + "). Item count:" + mState.getItemCount());
+ }
+ boolean fromScrapOrHiddenOrCache = false;
+ ViewHolder holder = null;
+ // 0) If there is a changed scrap, try to find from there
+ if (mState.isPreLayout()) {
+ holder = getChangedScrapViewForPosition(position);
+ fromScrapOrHiddenOrCache = holder != null;
+ }
+ // 1) Find by position from scrap/hidden list/cache
+ if (holder == null) {
+ holder = getScrapOrHiddenOrCachedHolderForPosition(position, dryRun);
+ if (holder != null) {
+ if (!validateViewHolderForOffsetPosition(holder)) {
+ // recycle holder (and unscrap if relevant) since it can't be used
+ if (!dryRun) {
+ // we would like to recycle this but need to make sure it is not used by
+ // animation logic etc.
+ holder.addFlags(ViewHolder.FLAG_INVALID);
+ if (holder.isScrap()) {
+ removeDetachedView(holder.itemView, false);
+ holder.unScrap();
+ } else if (holder.wasReturnedFromScrap()) {
+ holder.clearReturnedFromScrapFlag();
+ }
+ recycleViewHolderInternal(holder);
+ }
+ holder = null;
+ } else {
+ fromScrapOrHiddenOrCache = true;
+ }
+ }
+ }
+ if (holder == null) {
+ final int offsetPosition = mAdapterHelper.findPositionOffset(position);
+ if (offsetPosition < 0 || offsetPosition >= mAdapter.getItemCount()) {
+ throw new IndexOutOfBoundsException("Inconsistency detected. Invalid item "
+ + "position " + position + "(offset:" + offsetPosition + ")."
+ + "state:" + mState.getItemCount());
+ }
+
+ final int type = mAdapter.getItemViewType(offsetPosition);
+ // 2) Find from scrap/cache via stable ids, if exists
+ if (mAdapter.hasStableIds()) {
+ holder = getScrapOrCachedViewForId(mAdapter.getItemId(offsetPosition),
+ type, dryRun);
+ if (holder != null) {
+ // update position
+ holder.mPosition = offsetPosition;
+ fromScrapOrHiddenOrCache = true;
+ }
+ }
+ if (holder == null && mViewCacheExtension != null) {
+ // We are NOT sending the offsetPosition because LayoutManager does not
+ // know it.
+ final View view = mViewCacheExtension
+ .getViewForPositionAndType(this, position, type);
+ if (view != null) {
+ holder = getChildViewHolder(view);
+ if (holder == null) {
+ throw new IllegalArgumentException("getViewForPositionAndType returned"
+ + " a view which does not have a ViewHolder");
+ } else if (holder.shouldIgnore()) {
+ throw new IllegalArgumentException("getViewForPositionAndType returned"
+ + " a view that is ignored. You must call stopIgnoring before"
+ + " returning this view.");
+ }
+ }
+ }
+ if (holder == null) { // fallback to pool
+ if (DEBUG) {
+ Log.d(TAG, "tryGetViewHolderForPositionByDeadline("
+ + position + ") fetching from shared pool");
+ }
+ holder = getRecycledViewPool().getRecycledView(type);
+ if (holder != null) {
+ holder.resetInternal();
+ if (FORCE_INVALIDATE_DISPLAY_LIST) {
+ invalidateDisplayListInt(holder);
+ }
+ }
+ }
+ if (holder == null) {
+ long start = getNanoTime();
+ if (deadlineNs != FOREVER_NS
+ && !mRecyclerPool.willCreateInTime(type, start, deadlineNs)) {
+ // abort - we have a deadline we can't meet
+ return null;
+ }
+ holder = mAdapter.createViewHolder(RecyclerView.this, type);
+ if (ALLOW_THREAD_GAP_WORK) {
+ // only bother finding nested RV if prefetching
+ RecyclerView innerView = findNestedRecyclerView(holder.itemView);
+ if (innerView != null) {
+ holder.mNestedRecyclerView = new WeakReference<>(innerView);
+ }
+ }
+
+ long end = getNanoTime();
+ mRecyclerPool.factorInCreateTime(type, end - start);
+ if (DEBUG) {
+ Log.d(TAG, "tryGetViewHolderForPositionByDeadline created new ViewHolder");
+ }
+ }
+ }
+
+ // This is very ugly but the only place we can grab this information
+ // before the View is rebound and returned to the LayoutManager for post layout ops.
+ // We don't need this in pre-layout since the VH is not updated by the LM.
+ if (fromScrapOrHiddenOrCache && !mState.isPreLayout() && holder
+ .hasAnyOfTheFlags(ViewHolder.FLAG_BOUNCED_FROM_HIDDEN_LIST)) {
+ holder.setFlags(0, ViewHolder.FLAG_BOUNCED_FROM_HIDDEN_LIST);
+ if (mState.mRunSimpleAnimations) {
+ int changeFlags = ItemAnimator
+ .buildAdapterChangeFlagsForAnimations(holder);
+ changeFlags |= ItemAnimator.FLAG_APPEARED_IN_PRE_LAYOUT;
+ final ItemHolderInfo info = mItemAnimator.recordPreLayoutInformation(mState,
+ holder, changeFlags, holder.getUnmodifiedPayloads());
+ recordAnimationInfoIfBouncedHiddenView(holder, info);
+ }
+ }
+
+ boolean bound = false;
+ if (mState.isPreLayout() && holder.isBound()) {
+ // do not update unless we absolutely have to.
+ holder.mPreLayoutPosition = position;
+ } else if (!holder.isBound() || holder.needsUpdate() || holder.isInvalid()) {
+ if (DEBUG && holder.isRemoved()) {
+ throw new IllegalStateException("Removed holder should be bound and it should"
+ + " come here only in pre-layout. Holder: " + holder);
+ }
+ final int offsetPosition = mAdapterHelper.findPositionOffset(position);
+ bound = tryBindViewHolderByDeadline(holder, offsetPosition, position, deadlineNs);
+ }
+
+ final ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();
+ final LayoutParams rvLayoutParams;
+ if (lp == null) {
+ rvLayoutParams = (LayoutParams) generateDefaultLayoutParams();
+ holder.itemView.setLayoutParams(rvLayoutParams);
+ } else if (!checkLayoutParams(lp)) {
+ rvLayoutParams = (LayoutParams) generateLayoutParams(lp);
+ holder.itemView.setLayoutParams(rvLayoutParams);
+ } else {
+ rvLayoutParams = (LayoutParams) lp;
+ }
+ rvLayoutParams.mViewHolder = holder;
+ rvLayoutParams.mPendingInvalidate = fromScrapOrHiddenOrCache && bound;
+ return holder;
+ }
+
+ private void attachAccessibilityDelegate(View itemView) {
+ if (isAccessibilityEnabled()) {
+ if (itemView.getImportantForAccessibility()
+ == View.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
+ itemView.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
+ }
+
+ if (itemView.getAccessibilityDelegate() == null) {
+ itemView.setAccessibilityDelegate(mAccessibilityDelegate.getItemDelegate());
+ }
+ }
+ }
+
+ private void invalidateDisplayListInt(ViewHolder holder) {
+ if (holder.itemView instanceof ViewGroup) {
+ invalidateDisplayListInt((ViewGroup) holder.itemView, false);
+ }
+ }
+
+ private void invalidateDisplayListInt(ViewGroup viewGroup, boolean invalidateThis) {
+ for (int i = viewGroup.getChildCount() - 1; i >= 0; i--) {
+ final View view = viewGroup.getChildAt(i);
+ if (view instanceof ViewGroup) {
+ invalidateDisplayListInt((ViewGroup) view, true);
+ }
+ }
+ if (!invalidateThis) {
+ return;
+ }
+ // we need to force it to become invisible
+ if (viewGroup.getVisibility() == View.INVISIBLE) {
+ viewGroup.setVisibility(View.VISIBLE);
+ viewGroup.setVisibility(View.INVISIBLE);
+ } else {
+ final int visibility = viewGroup.getVisibility();
+ viewGroup.setVisibility(View.INVISIBLE);
+ viewGroup.setVisibility(visibility);
+ }
+ }
+
+ /**
+ * Recycle a detached view. The specified view will be added to a pool of views
+ * for later rebinding and reuse.
+ *
+ * <p>A view must be fully detached (removed from parent) before it may be recycled. If the
+ * View is scrapped, it will be removed from scrap list.</p>
+ *
+ * @param view Removed view for recycling
+ * @see LayoutManager#removeAndRecycleView(View, Recycler)
+ */
+ public void recycleView(View view) {
+ // This public recycle method tries to make view recycle-able since layout manager
+ // intended to recycle this view (e.g. even if it is in scrap or change cache)
+ ViewHolder holder = getChildViewHolderInt(view);
+ if (holder.isTmpDetached()) {
+ removeDetachedView(view, false);
+ }
+ if (holder.isScrap()) {
+ holder.unScrap();
+ } else if (holder.wasReturnedFromScrap()) {
+ holder.clearReturnedFromScrapFlag();
+ }
+ recycleViewHolderInternal(holder);
+ }
+
+ /**
+ * Internally, use this method instead of {@link #recycleView(android.view.View)} to
+ * catch potential bugs.
+ * @param view
+ */
+ void recycleViewInternal(View view) {
+ recycleViewHolderInternal(getChildViewHolderInt(view));
+ }
+
+ void recycleAndClearCachedViews() {
+ final int count = mCachedViews.size();
+ for (int i = count - 1; i >= 0; i--) {
+ recycleCachedViewAt(i);
+ }
+ mCachedViews.clear();
+ if (ALLOW_THREAD_GAP_WORK) {
+ mPrefetchRegistry.clearPrefetchPositions();
+ }
+ }
+
+ /**
+ * Recycles a cached view and removes the view from the list. Views are added to cache
+ * if and only if they are recyclable, so this method does not check it again.
+ * <p>
+ * A small exception to this rule is when the view does not have an animator reference
+ * but transient state is true (due to animations created outside ItemAnimator). In that
+ * case, adapter may choose to recycle it. From RecyclerView's perspective, the view is
+ * still recyclable since Adapter wants to do so.
+ *
+ * @param cachedViewIndex The index of the view in cached views list
+ */
+ void recycleCachedViewAt(int cachedViewIndex) {
+ if (DEBUG) {
+ Log.d(TAG, "Recycling cached view at index " + cachedViewIndex);
+ }
+ ViewHolder viewHolder = mCachedViews.get(cachedViewIndex);
+ if (DEBUG) {
+ Log.d(TAG, "CachedViewHolder to be recycled: " + viewHolder);
+ }
+ addViewHolderToRecycledViewPool(viewHolder, true);
+ mCachedViews.remove(cachedViewIndex);
+ }
+
+ /**
+ * internal implementation checks if view is scrapped or attached and throws an exception
+ * if so.
+ * Public version un-scraps before calling recycle.
+ */
+ void recycleViewHolderInternal(ViewHolder holder) {
+ if (holder.isScrap() || holder.itemView.getParent() != null) {
+ throw new IllegalArgumentException(
+ "Scrapped or attached views may not be recycled. isScrap:"
+ + holder.isScrap() + " isAttached:"
+ + (holder.itemView.getParent() != null));
+ }
+
+ if (holder.isTmpDetached()) {
+ throw new IllegalArgumentException("Tmp detached view should be removed "
+ + "from RecyclerView before it can be recycled: " + holder);
+ }
+
+ if (holder.shouldIgnore()) {
+ throw new IllegalArgumentException("Trying to recycle an ignored view holder. You"
+ + " should first call stopIgnoringView(view) before calling recycle.");
+ }
+ //noinspection unchecked
+ final boolean transientStatePreventsRecycling = holder
+ .doesTransientStatePreventRecycling();
+ final boolean forceRecycle = mAdapter != null
+ && transientStatePreventsRecycling
+ && mAdapter.onFailedToRecycleView(holder);
+ boolean cached = false;
+ boolean recycled = false;
+ if (DEBUG && mCachedViews.contains(holder)) {
+ throw new IllegalArgumentException("cached view received recycle internal? "
+ + holder);
+ }
+ if (forceRecycle || holder.isRecyclable()) {
+ if (mViewCacheMax > 0
+ && !holder.hasAnyOfTheFlags(ViewHolder.FLAG_INVALID
+ | ViewHolder.FLAG_REMOVED
+ | ViewHolder.FLAG_UPDATE
+ | ViewHolder.FLAG_ADAPTER_POSITION_UNKNOWN)) {
+ // Retire oldest cached view
+ int cachedViewSize = mCachedViews.size();
+ if (cachedViewSize >= mViewCacheMax && cachedViewSize > 0) {
+ recycleCachedViewAt(0);
+ cachedViewSize--;
+ }
+
+ int targetCacheIndex = cachedViewSize;
+ if (ALLOW_THREAD_GAP_WORK
+ && cachedViewSize > 0
+ && !mPrefetchRegistry.lastPrefetchIncludedPosition(holder.mPosition)) {
+ // when adding the view, skip past most recently prefetched views
+ int cacheIndex = cachedViewSize - 1;
+ while (cacheIndex >= 0) {
+ int cachedPos = mCachedViews.get(cacheIndex).mPosition;
+ if (!mPrefetchRegistry.lastPrefetchIncludedPosition(cachedPos)) {
+ break;
+ }
+ cacheIndex--;
+ }
+ targetCacheIndex = cacheIndex + 1;
+ }
+ mCachedViews.add(targetCacheIndex, holder);
+ cached = true;
+ }
+ if (!cached) {
+ addViewHolderToRecycledViewPool(holder, true);
+ recycled = true;
+ }
+ } else {
+ // NOTE: A view can fail to be recycled when it is scrolled off while an animation
+ // runs. In this case, the item is eventually recycled by
+ // ItemAnimatorRestoreListener#onAnimationFinished.
+
+ // TODO: consider cancelling an animation when an item is removed scrollBy,
+ // to return it to the pool faster
+ if (DEBUG) {
+ Log.d(TAG, "trying to recycle a non-recycleable holder. Hopefully, it will "
+ + "re-visit here. We are still removing it from animation lists");
+ }
+ }
+ // even if the holder is not removed, we still call this method so that it is removed
+ // from view holder lists.
+ mViewInfoStore.removeViewHolder(holder);
+ if (!cached && !recycled && transientStatePreventsRecycling) {
+ holder.mOwnerRecyclerView = null;
+ }
+ }
+
+ /**
+ * Prepares the ViewHolder to be removed/recycled, and inserts it into the RecycledViewPool.
+ *
+ * Pass false to dispatchRecycled for views that have not been bound.
+ *
+ * @param holder Holder to be added to the pool.
+ * @param dispatchRecycled True to dispatch View recycled callbacks.
+ */
+ void addViewHolderToRecycledViewPool(ViewHolder holder, boolean dispatchRecycled) {
+ clearNestedRecyclerViewIfNotNested(holder);
+ holder.itemView.setAccessibilityDelegate(null);
+ if (dispatchRecycled) {
+ dispatchViewRecycled(holder);
+ }
+ holder.mOwnerRecyclerView = null;
+ getRecycledViewPool().putRecycledView(holder);
+ }
+
+ /**
+ * Used as a fast path for unscrapping and recycling a view during a bulk operation.
+ * The caller must call {@link #clearScrap()} when it's done to update the recycler's
+ * internal bookkeeping.
+ */
+ void quickRecycleScrapView(View view) {
+ final ViewHolder holder = getChildViewHolderInt(view);
+ holder.mScrapContainer = null;
+ holder.mInChangeScrap = false;
+ holder.clearReturnedFromScrapFlag();
+ recycleViewHolderInternal(holder);
+ }
+
+ /**
+ * Mark an attached view as scrap.
+ *
+ * <p>"Scrap" views are still attached to their parent RecyclerView but are eligible
+ * for rebinding and reuse. Requests for a view for a given position may return a
+ * reused or rebound scrap view instance.</p>
+ *
+ * @param view View to scrap
+ */
+ void scrapView(View view) {
+ final ViewHolder holder = getChildViewHolderInt(view);
+ if (holder.hasAnyOfTheFlags(ViewHolder.FLAG_REMOVED | ViewHolder.FLAG_INVALID)
+ || !holder.isUpdated() || canReuseUpdatedViewHolder(holder)) {
+ if (holder.isInvalid() && !holder.isRemoved() && !mAdapter.hasStableIds()) {
+ throw new IllegalArgumentException("Called scrap view with an invalid view."
+ + " Invalid views cannot be reused from scrap, they should rebound from"
+ + " recycler pool.");
+ }
+ holder.setScrapContainer(this, false);
+ mAttachedScrap.add(holder);
+ } else {
+ if (mChangedScrap == null) {
+ mChangedScrap = new ArrayList<ViewHolder>();
+ }
+ holder.setScrapContainer(this, true);
+ mChangedScrap.add(holder);
+ }
+ }
+
+ /**
+ * Remove a previously scrapped view from the pool of eligible scrap.
+ *
+ * <p>This view will no longer be eligible for reuse until re-scrapped or
+ * until it is explicitly removed and recycled.</p>
+ */
+ void unscrapView(ViewHolder holder) {
+ if (holder.mInChangeScrap) {
+ mChangedScrap.remove(holder);
+ } else {
+ mAttachedScrap.remove(holder);
+ }
+ holder.mScrapContainer = null;
+ holder.mInChangeScrap = false;
+ holder.clearReturnedFromScrapFlag();
+ }
+
+ int getScrapCount() {
+ return mAttachedScrap.size();
+ }
+
+ View getScrapViewAt(int index) {
+ return mAttachedScrap.get(index).itemView;
+ }
+
+ void clearScrap() {
+ mAttachedScrap.clear();
+ if (mChangedScrap != null) {
+ mChangedScrap.clear();
+ }
+ }
+
+ ViewHolder getChangedScrapViewForPosition(int position) {
+ // If pre-layout, check the changed scrap for an exact match.
+ final int changedScrapSize;
+ if (mChangedScrap == null || (changedScrapSize = mChangedScrap.size()) == 0) {
+ return null;
+ }
+ // find by position
+ for (int i = 0; i < changedScrapSize; i++) {
+ final ViewHolder holder = mChangedScrap.get(i);
+ if (!holder.wasReturnedFromScrap() && holder.getLayoutPosition() == position) {
+ holder.addFlags(ViewHolder.FLAG_RETURNED_FROM_SCRAP);
+ return holder;
+ }
+ }
+ // find by id
+ if (mAdapter.hasStableIds()) {
+ final int offsetPosition = mAdapterHelper.findPositionOffset(position);
+ if (offsetPosition > 0 && offsetPosition < mAdapter.getItemCount()) {
+ final long id = mAdapter.getItemId(offsetPosition);
+ for (int i = 0; i < changedScrapSize; i++) {
+ final ViewHolder holder = mChangedScrap.get(i);
+ if (!holder.wasReturnedFromScrap() && holder.getItemId() == id) {
+ holder.addFlags(ViewHolder.FLAG_RETURNED_FROM_SCRAP);
+ return holder;
+ }
+ }
+ }
+ }
+ return null;
+ }
+
+ /**
+ * Returns a view for the position either from attach scrap, hidden children, or cache.
+ *
+ * @param position Item position
+ * @param dryRun Does a dry run, finds the ViewHolder but does not remove
+ * @return a ViewHolder that can be re-used for this position.
+ */
+ ViewHolder getScrapOrHiddenOrCachedHolderForPosition(int position, boolean dryRun) {
+ final int scrapCount = mAttachedScrap.size();
+
+ // Try first for an exact, non-invalid match from scrap.
+ for (int i = 0; i < scrapCount; i++) {
+ final ViewHolder holder = mAttachedScrap.get(i);
+ if (!holder.wasReturnedFromScrap() && holder.getLayoutPosition() == position
+ && !holder.isInvalid() && (mState.mInPreLayout || !holder.isRemoved())) {
+ holder.addFlags(ViewHolder.FLAG_RETURNED_FROM_SCRAP);
+ return holder;
+ }
+ }
+
+ if (!dryRun) {
+ View view = mChildHelper.findHiddenNonRemovedView(position);
+ if (view != null) {
+ // This View is good to be used. We just need to unhide, detach and move to the
+ // scrap list.
+ final ViewHolder vh = getChildViewHolderInt(view);
+ mChildHelper.unhide(view);
+ int layoutIndex = mChildHelper.indexOfChild(view);
+ if (layoutIndex == RecyclerView.NO_POSITION) {
+ throw new IllegalStateException("layout index should not be -1 after "
+ + "unhiding a view:" + vh);
+ }
+ mChildHelper.detachViewFromParent(layoutIndex);
+ scrapView(view);
+ vh.addFlags(ViewHolder.FLAG_RETURNED_FROM_SCRAP
+ | ViewHolder.FLAG_BOUNCED_FROM_HIDDEN_LIST);
+ return vh;
+ }
+ }
+
+ // Search in our first-level recycled view cache.
+ final int cacheSize = mCachedViews.size();
+ for (int i = 0; i < cacheSize; i++) {
+ final ViewHolder holder = mCachedViews.get(i);
+ // invalid view holders may be in cache if adapter has stable ids as they can be
+ // retrieved via getScrapOrCachedViewForId
+ if (!holder.isInvalid() && holder.getLayoutPosition() == position) {
+ if (!dryRun) {
+ mCachedViews.remove(i);
+ }
+ if (DEBUG) {
+ Log.d(TAG, "getScrapOrHiddenOrCachedHolderForPosition(" + position
+ + ") found match in cache: " + holder);
+ }
+ return holder;
+ }
+ }
+ return null;
+ }
+
+ ViewHolder getScrapOrCachedViewForId(long id, int type, boolean dryRun) {
+ // Look in our attached views first
+ final int count = mAttachedScrap.size();
+ for (int i = count - 1; i >= 0; i--) {
+ final ViewHolder holder = mAttachedScrap.get(i);
+ if (holder.getItemId() == id && !holder.wasReturnedFromScrap()) {
+ if (type == holder.getItemViewType()) {
+ holder.addFlags(ViewHolder.FLAG_RETURNED_FROM_SCRAP);
+ if (holder.isRemoved()) {
+ // this might be valid in two cases:
+ // > item is removed but we are in pre-layout pass
+ // >> do nothing. return as is. make sure we don't rebind
+ // > item is removed then added to another position and we are in
+ // post layout.
+ // >> remove removed and invalid flags, add update flag to rebind
+ // because item was invisible to us and we don't know what happened in
+ // between.
+ if (!mState.isPreLayout()) {
+ holder.setFlags(ViewHolder.FLAG_UPDATE, ViewHolder.FLAG_UPDATE
+ | ViewHolder.FLAG_INVALID | ViewHolder.FLAG_REMOVED);
+ }
+ }
+ return holder;
+ } else if (!dryRun) {
+ // if we are running animations, it is actually better to keep it in scrap
+ // but this would force layout manager to lay it out which would be bad.
+ // Recycle this scrap. Type mismatch.
+ mAttachedScrap.remove(i);
+ removeDetachedView(holder.itemView, false);
+ quickRecycleScrapView(holder.itemView);
+ }
+ }
+ }
+
+ // Search the first-level cache
+ final int cacheSize = mCachedViews.size();
+ for (int i = cacheSize - 1; i >= 0; i--) {
+ final ViewHolder holder = mCachedViews.get(i);
+ if (holder.getItemId() == id) {
+ if (type == holder.getItemViewType()) {
+ if (!dryRun) {
+ mCachedViews.remove(i);
+ }
+ return holder;
+ } else if (!dryRun) {
+ recycleCachedViewAt(i);
+ return null;
+ }
+ }
+ }
+ return null;
+ }
+
+ void dispatchViewRecycled(ViewHolder holder) {
+ if (mRecyclerListener != null) {
+ mRecyclerListener.onViewRecycled(holder);
+ }
+ if (mAdapter != null) {
+ mAdapter.onViewRecycled(holder);
+ }
+ if (mState != null) {
+ mViewInfoStore.removeViewHolder(holder);
+ }
+ if (DEBUG) Log.d(TAG, "dispatchViewRecycled: " + holder);
+ }
+
+ void onAdapterChanged(Adapter oldAdapter, Adapter newAdapter,
+ boolean compatibleWithPrevious) {
+ clear();
+ getRecycledViewPool().onAdapterChanged(oldAdapter, newAdapter, compatibleWithPrevious);
+ }
+
+ void offsetPositionRecordsForMove(int from, int to) {
+ final int start, end, inBetweenOffset;
+ if (from < to) {
+ start = from;
+ end = to;
+ inBetweenOffset = -1;
+ } else {
+ start = to;
+ end = from;
+ inBetweenOffset = 1;
+ }
+ final int cachedCount = mCachedViews.size();
+ for (int i = 0; i < cachedCount; i++) {
+ final ViewHolder holder = mCachedViews.get(i);
+ if (holder == null || holder.mPosition < start || holder.mPosition > end) {
+ continue;
+ }
+ if (holder.mPosition == from) {
+ holder.offsetPosition(to - from, false);
+ } else {
+ holder.offsetPosition(inBetweenOffset, false);
+ }
+ if (DEBUG) {
+ Log.d(TAG, "offsetPositionRecordsForMove cached child " + i + " holder "
+ + holder);
+ }
+ }
+ }
+
+ void offsetPositionRecordsForInsert(int insertedAt, int count) {
+ final int cachedCount = mCachedViews.size();
+ for (int i = 0; i < cachedCount; i++) {
+ final ViewHolder holder = mCachedViews.get(i);
+ if (holder != null && holder.mPosition >= insertedAt) {
+ if (DEBUG) {
+ Log.d(TAG, "offsetPositionRecordsForInsert cached " + i + " holder "
+ + holder + " now at position " + (holder.mPosition + count));
+ }
+ holder.offsetPosition(count, true);
+ }
+ }
+ }
+
+ /**
+ * @param removedFrom Remove start index
+ * @param count Remove count
+ * @param applyToPreLayout If true, changes will affect ViewHolder's pre-layout position, if
+ * false, they'll be applied before the second layout pass
+ */
+ void offsetPositionRecordsForRemove(int removedFrom, int count, boolean applyToPreLayout) {
+ final int removedEnd = removedFrom + count;
+ final int cachedCount = mCachedViews.size();
+ for (int i = cachedCount - 1; i >= 0; i--) {
+ final ViewHolder holder = mCachedViews.get(i);
+ if (holder != null) {
+ if (holder.mPosition >= removedEnd) {
+ if (DEBUG) {
+ Log.d(TAG, "offsetPositionRecordsForRemove cached " + i
+ + " holder " + holder + " now at position "
+ + (holder.mPosition - count));
+ }
+ holder.offsetPosition(-count, applyToPreLayout);
+ } else if (holder.mPosition >= removedFrom) {
+ // Item for this view was removed. Dump it from the cache.
+ holder.addFlags(ViewHolder.FLAG_REMOVED);
+ recycleCachedViewAt(i);
+ }
+ }
+ }
+ }
+
+ void setViewCacheExtension(ViewCacheExtension extension) {
+ mViewCacheExtension = extension;
+ }
+
+ void setRecycledViewPool(RecycledViewPool pool) {
+ if (mRecyclerPool != null) {
+ mRecyclerPool.detach();
+ }
+ mRecyclerPool = pool;
+ if (pool != null) {
+ mRecyclerPool.attach(getAdapter());
+ }
+ }
+
+ RecycledViewPool getRecycledViewPool() {
+ if (mRecyclerPool == null) {
+ mRecyclerPool = new RecycledViewPool();
+ }
+ return mRecyclerPool;
+ }
+
+ void viewRangeUpdate(int positionStart, int itemCount) {
+ final int positionEnd = positionStart + itemCount;
+ final int cachedCount = mCachedViews.size();
+ for (int i = cachedCount - 1; i >= 0; i--) {
+ final ViewHolder holder = mCachedViews.get(i);
+ if (holder == null) {
+ continue;
+ }
+
+ final int pos = holder.getLayoutPosition();
+ if (pos >= positionStart && pos < positionEnd) {
+ holder.addFlags(ViewHolder.FLAG_UPDATE);
+ recycleCachedViewAt(i);
+ // cached views should not be flagged as changed because this will cause them
+ // to animate when they are returned from cache.
+ }
+ }
+ }
+
+ void setAdapterPositionsAsUnknown() {
+ final int cachedCount = mCachedViews.size();
+ for (int i = 0; i < cachedCount; i++) {
+ final ViewHolder holder = mCachedViews.get(i);
+ if (holder != null) {
+ holder.addFlags(ViewHolder.FLAG_ADAPTER_POSITION_UNKNOWN);
+ }
+ }
+ }
+
+ void markKnownViewsInvalid() {
+ if (mAdapter != null && mAdapter.hasStableIds()) {
+ final int cachedCount = mCachedViews.size();
+ for (int i = 0; i < cachedCount; i++) {
+ final ViewHolder holder = mCachedViews.get(i);
+ if (holder != null) {
+ holder.addFlags(ViewHolder.FLAG_UPDATE | ViewHolder.FLAG_INVALID);
+ holder.addChangePayload(null);
+ }
+ }
+ } else {
+ // we cannot re-use cached views in this case. Recycle them all
+ recycleAndClearCachedViews();
+ }
+ }
+
+ void clearOldPositions() {
+ final int cachedCount = mCachedViews.size();
+ for (int i = 0; i < cachedCount; i++) {
+ final ViewHolder holder = mCachedViews.get(i);
+ holder.clearOldPosition();
+ }
+ final int scrapCount = mAttachedScrap.size();
+ for (int i = 0; i < scrapCount; i++) {
+ mAttachedScrap.get(i).clearOldPosition();
+ }
+ if (mChangedScrap != null) {
+ final int changedScrapCount = mChangedScrap.size();
+ for (int i = 0; i < changedScrapCount; i++) {
+ mChangedScrap.get(i).clearOldPosition();
+ }
+ }
+ }
+
+ void markItemDecorInsetsDirty() {
+ final int cachedCount = mCachedViews.size();
+ for (int i = 0; i < cachedCount; i++) {
+ final ViewHolder holder = mCachedViews.get(i);
+ LayoutParams layoutParams = (LayoutParams) holder.itemView.getLayoutParams();
+ if (layoutParams != null) {
+ layoutParams.mInsetsDirty = true;
+ }
+ }
+ }
+ }
+
+ /**
+ * ViewCacheExtension is a helper class to provide an additional layer of view caching that can
+ * be controlled by the developer.
+ * <p>
+ * When {@link Recycler#getViewForPosition(int)} is called, Recycler checks attached scrap and
+ * first level cache to find a matching View. If it cannot find a suitable View, Recycler will
+ * call the {@link #getViewForPositionAndType(Recycler, int, int)} before checking
+ * {@link RecycledViewPool}.
+ * <p>
+ * Note that, Recycler never sends Views to this method to be cached. It is developers
+ * responsibility to decide whether they want to keep their Views in this custom cache or let
+ * the default recycling policy handle it.
+ */
+ public abstract static class ViewCacheExtension {
+
+ /**
+ * Returns a View that can be binded to the given Adapter position.
+ * <p>
+ * This method should <b>not</b> create a new View. Instead, it is expected to return
+ * an already created View that can be re-used for the given type and position.
+ * If the View is marked as ignored, it should first call
+ * {@link LayoutManager#stopIgnoringView(View)} before returning the View.
+ * <p>
+ * RecyclerView will re-bind the returned View to the position if necessary.
+ *
+ * @param recycler The Recycler that can be used to bind the View
+ * @param position The adapter position
+ * @param type The type of the View, defined by adapter
+ * @return A View that is bound to the given position or NULL if there is no View to re-use
+ * @see LayoutManager#ignoreView(View)
+ */
+ public abstract View getViewForPositionAndType(Recycler recycler, int position, int type);
+ }
+
+ /**
+ * Base class for an Adapter
+ *
+ * <p>Adapters provide a binding from an app-specific data set to views that are displayed
+ * within a {@link RecyclerView}.</p>
+ *
+ * @param <VH> A class that extends ViewHolder that will be used by the adapter.
+ */
+ public abstract static class Adapter<VH extends ViewHolder> {
+ private final AdapterDataObservable mObservable = new AdapterDataObservable();
+ private boolean mHasStableIds = false;
+
+ /**
+ * Called when RecyclerView needs a new {@link ViewHolder} of the given type to represent
+ * an item.
+ * <p>
+ * This new ViewHolder should be constructed with a new View that can represent the items
+ * of the given type. You can either create a new View manually or inflate it from an XML
+ * layout file.
+ * <p>
+ * The new ViewHolder will be used to display items of the adapter using
+ * {@link #onBindViewHolder(ViewHolder, int, List)}. Since it will be re-used to display
+ * different items in the data set, it is a good idea to cache references to sub views of
+ * the View to avoid unnecessary {@link View#findViewById(int)} calls.
+ *
+ * @param parent The ViewGroup into which the new View will be added after it is bound to
+ * an adapter position.
+ * @param viewType The view type of the new View.
+ *
+ * @return A new ViewHolder that holds a View of the given view type.
+ * @see #getItemViewType(int)
+ * @see #onBindViewHolder(ViewHolder, int)
+ */
+ public abstract VH onCreateViewHolder(ViewGroup parent, int viewType);
+
+ /**
+ * Called by RecyclerView to display the data at the specified position. This method should
+ * update the contents of the {@link ViewHolder#itemView} to reflect the item at the given
+ * position.
+ * <p>
+ * Note that unlike {@link android.widget.ListView}, RecyclerView will not call this method
+ * again if the position of the item changes in the data set unless the item itself is
+ * invalidated or the new position cannot be determined. For this reason, you should only
+ * use the <code>position</code> parameter while acquiring the related data item inside
+ * this method and should not keep a copy of it. If you need the position of an item later
+ * on (e.g. in a click listener), use {@link ViewHolder#getAdapterPosition()} which will
+ * have the updated adapter position.
+ *
+ * Override {@link #onBindViewHolder(ViewHolder, int, List)} instead if Adapter can
+ * handle efficient partial bind.
+ *
+ * @param holder The ViewHolder which should be updated to represent the contents of the
+ * item at the given position in the data set.
+ * @param position The position of the item within the adapter's data set.
+ */
+ public abstract void onBindViewHolder(VH holder, int position);
+
+ /**
+ * Called by RecyclerView to display the data at the specified position. This method
+ * should update the contents of the {@link ViewHolder#itemView} to reflect the item at
+ * the given position.
+ * <p>
+ * Note that unlike {@link android.widget.ListView}, RecyclerView will not call this method
+ * again if the position of the item changes in the data set unless the item itself is
+ * invalidated or the new position cannot be determined. For this reason, you should only
+ * use the <code>position</code> parameter while acquiring the related data item inside
+ * this method and should not keep a copy of it. If you need the position of an item later
+ * on (e.g. in a click listener), use {@link ViewHolder#getAdapterPosition()} which will
+ * have the updated adapter position.
+ * <p>
+ * Partial bind vs full bind:
+ * <p>
+ * The payloads parameter is a merge list from {@link #notifyItemChanged(int, Object)} or
+ * {@link #notifyItemRangeChanged(int, int, Object)}. If the payloads list is not empty,
+ * the ViewHolder is currently bound to old data and Adapter may run an efficient partial
+ * update using the payload info. If the payload is empty, Adapter must run a full bind.
+ * Adapter should not assume that the payload passed in notify methods will be received by
+ * onBindViewHolder(). For example when the view is not attached to the screen, the
+ * payload in notifyItemChange() will be simply dropped.
+ *
+ * @param holder The ViewHolder which should be updated to represent the contents of the
+ * item at the given position in the data set.
+ * @param position The position of the item within the adapter's data set.
+ * @param payloads A non-null list of merged payloads. Can be empty list if requires full
+ * update.
+ */
+ public void onBindViewHolder(VH holder, int position, List<Object> payloads) {
+ onBindViewHolder(holder, position);
+ }
+
+ /**
+ * This method calls {@link #onCreateViewHolder(ViewGroup, int)} to create a new
+ * {@link ViewHolder} and initializes some private fields to be used by RecyclerView.
+ *
+ * @see #onCreateViewHolder(ViewGroup, int)
+ */
+ public final VH createViewHolder(ViewGroup parent, int viewType) {
+ Trace.beginSection(TRACE_CREATE_VIEW_TAG);
+ final VH holder = onCreateViewHolder(parent, viewType);
+ holder.mItemViewType = viewType;
+ Trace.endSection();
+ return holder;
+ }
+
+ /**
+ * This method internally calls {@link #onBindViewHolder(ViewHolder, int)} to update the
+ * {@link ViewHolder} contents with the item at the given position and also sets up some
+ * private fields to be used by RecyclerView.
+ *
+ * @see #onBindViewHolder(ViewHolder, int)
+ */
+ public final void bindViewHolder(VH holder, int position) {
+ holder.mPosition = position;
+ if (hasStableIds()) {
+ holder.mItemId = getItemId(position);
+ }
+ holder.setFlags(ViewHolder.FLAG_BOUND,
+ ViewHolder.FLAG_BOUND | ViewHolder.FLAG_UPDATE | ViewHolder.FLAG_INVALID
+ | ViewHolder.FLAG_ADAPTER_POSITION_UNKNOWN);
+ Trace.beginSection(TRACE_BIND_VIEW_TAG);
+ onBindViewHolder(holder, position, holder.getUnmodifiedPayloads());
+ holder.clearPayload();
+ final ViewGroup.LayoutParams layoutParams = holder.itemView.getLayoutParams();
+ if (layoutParams instanceof RecyclerView.LayoutParams) {
+ ((LayoutParams) layoutParams).mInsetsDirty = true;
+ }
+ Trace.endSection();
+ }
+
+ /**
+ * Return the view type of the item at <code>position</code> for the purposes
+ * of view recycling.
+ *
+ * <p>The default implementation of this method returns 0, making the assumption of
+ * a single view type for the adapter. Unlike ListView adapters, types need not
+ * be contiguous. Consider using id resources to uniquely identify item view types.
+ *
+ * @param position position to query
+ * @return integer value identifying the type of the view needed to represent the item at
+ * <code>position</code>. Type codes need not be contiguous.
+ */
+ public int getItemViewType(int position) {
+ return 0;
+ }
+
+ /**
+ * Indicates whether each item in the data set can be represented with a unique identifier
+ * of type {@link java.lang.Long}.
+ *
+ * @param hasStableIds Whether items in data set have unique identifiers or not.
+ * @see #hasStableIds()
+ * @see #getItemId(int)
+ */
+ public void setHasStableIds(boolean hasStableIds) {
+ if (hasObservers()) {
+ throw new IllegalStateException("Cannot change whether this adapter has "
+ + "stable IDs while the adapter has registered observers.");
+ }
+ mHasStableIds = hasStableIds;
+ }
+
+ /**
+ * Return the stable ID for the item at <code>position</code>. If {@link #hasStableIds()}
+ * would return false this method should return {@link #NO_ID}. The default implementation
+ * of this method returns {@link #NO_ID}.
+ *
+ * @param position Adapter position to query
+ * @return the stable ID of the item at position
+ */
+ public long getItemId(int position) {
+ return NO_ID;
+ }
+
+ /**
+ * Returns the total number of items in the data set held by the adapter.
+ *
+ * @return The total number of items in this adapter.
+ */
+ public abstract int getItemCount();
+
+ /**
+ * Returns true if this adapter publishes a unique <code>long</code> value that can
+ * act as a key for the item at a given position in the data set. If that item is relocated
+ * in the data set, the ID returned for that item should be the same.
+ *
+ * @return true if this adapter's items have stable IDs
+ */
+ public final boolean hasStableIds() {
+ return mHasStableIds;
+ }
+
+ /**
+ * Called when a view created by this adapter has been recycled.
+ *
+ * <p>A view is recycled when a {@link LayoutManager} decides that it no longer
+ * needs to be attached to its parent {@link RecyclerView}. This can be because it has
+ * fallen out of visibility or a set of cached views represented by views still
+ * attached to the parent RecyclerView. If an item view has large or expensive data
+ * bound to it such as large bitmaps, this may be a good place to release those
+ * resources.</p>
+ * <p>
+ * RecyclerView calls this method right before clearing ViewHolder's internal data and
+ * sending it to RecycledViewPool. This way, if ViewHolder was holding valid information
+ * before being recycled, you can call {@link ViewHolder#getAdapterPosition()} to get
+ * its adapter position.
+ *
+ * @param holder The ViewHolder for the view being recycled
+ */
+ public void onViewRecycled(VH holder) {
+ }
+
+ /**
+ * Called by the RecyclerView if a ViewHolder created by this Adapter cannot be recycled
+ * due to its transient state. Upon receiving this callback, Adapter can clear the
+ * animation(s) that effect the View's transient state and return <code>true</code> so that
+ * the View can be recycled. Keep in mind that the View in question is already removed from
+ * the RecyclerView.
+ * <p>
+ * In some cases, it is acceptable to recycle a View although it has transient state. Most
+ * of the time, this is a case where the transient state will be cleared in
+ * {@link #onBindViewHolder(ViewHolder, int)} call when View is rebound to a new position.
+ * For this reason, RecyclerView leaves the decision to the Adapter and uses the return
+ * value of this method to decide whether the View should be recycled or not.
+ * <p>
+ * Note that when all animations are created by {@link RecyclerView.ItemAnimator}, you
+ * should never receive this callback because RecyclerView keeps those Views as children
+ * until their animations are complete. This callback is useful when children of the item
+ * views create animations which may not be easy to implement using an {@link ItemAnimator}.
+ * <p>
+ * You should <em>never</em> fix this issue by calling
+ * <code>holder.itemView.setHasTransientState(false);</code> unless you've previously called
+ * <code>holder.itemView.setHasTransientState(true);</code>. Each
+ * <code>View.setHasTransientState(true)</code> call must be matched by a
+ * <code>View.setHasTransientState(false)</code> call, otherwise, the state of the View
+ * may become inconsistent. You should always prefer to end or cancel animations that are
+ * triggering the transient state instead of handling it manually.
+ *
+ * @param holder The ViewHolder containing the View that could not be recycled due to its
+ * transient state.
+ * @return True if the View should be recycled, false otherwise. Note that if this method
+ * returns <code>true</code>, RecyclerView <em>will ignore</em> the transient state of
+ * the View and recycle it regardless. If this method returns <code>false</code>,
+ * RecyclerView will check the View's transient state again before giving a final decision.
+ * Default implementation returns false.
+ */
+ public boolean onFailedToRecycleView(VH holder) {
+ return false;
+ }
+
+ /**
+ * Called when a view created by this adapter has been attached to a window.
+ *
+ * <p>This can be used as a reasonable signal that the view is about to be seen
+ * by the user. If the adapter previously freed any resources in
+ * {@link #onViewDetachedFromWindow(RecyclerView.ViewHolder) onViewDetachedFromWindow}
+ * those resources should be restored here.</p>
+ *
+ * @param holder Holder of the view being attached
+ */
+ public void onViewAttachedToWindow(VH holder) {
+ }
+
+ /**
+ * Called when a view created by this adapter has been detached from its window.
+ *
+ * <p>Becoming detached from the window is not necessarily a permanent condition;
+ * the consumer of an Adapter's views may choose to cache views offscreen while they
+ * are not visible, attaching and detaching them as appropriate.</p>
+ *
+ * @param holder Holder of the view being detached
+ */
+ public void onViewDetachedFromWindow(VH holder) {
+ }
+
+ /**
+ * Returns true if one or more observers are attached to this adapter.
+ *
+ * @return true if this adapter has observers
+ */
+ public final boolean hasObservers() {
+ return mObservable.hasObservers();
+ }
+
+ /**
+ * Register a new observer to listen for data changes.
+ *
+ * <p>The adapter may publish a variety of events describing specific changes.
+ * Not all adapters may support all change types and some may fall back to a generic
+ * {@link com.android.internal.widget.RecyclerView.AdapterDataObserver#onChanged()
+ * "something changed"} event if more specific data is not available.</p>
+ *
+ * <p>Components registering observers with an adapter are responsible for
+ * {@link #unregisterAdapterDataObserver(RecyclerView.AdapterDataObserver)
+ * unregistering} those observers when finished.</p>
+ *
+ * @param observer Observer to register
+ *
+ * @see #unregisterAdapterDataObserver(RecyclerView.AdapterDataObserver)
+ */
+ public void registerAdapterDataObserver(AdapterDataObserver observer) {
+ mObservable.registerObserver(observer);
+ }
+
+ /**
+ * Unregister an observer currently listening for data changes.
+ *
+ * <p>The unregistered observer will no longer receive events about changes
+ * to the adapter.</p>
+ *
+ * @param observer Observer to unregister
+ *
+ * @see #registerAdapterDataObserver(RecyclerView.AdapterDataObserver)
+ */
+ public void unregisterAdapterDataObserver(AdapterDataObserver observer) {
+ mObservable.unregisterObserver(observer);
+ }
+
+ /**
+ * Called by RecyclerView when it starts observing this Adapter.
+ * <p>
+ * Keep in mind that same adapter may be observed by multiple RecyclerViews.
+ *
+ * @param recyclerView The RecyclerView instance which started observing this adapter.
+ * @see #onDetachedFromRecyclerView(RecyclerView)
+ */
+ public void onAttachedToRecyclerView(RecyclerView recyclerView) {
+ }
+
+ /**
+ * Called by RecyclerView when it stops observing this Adapter.
+ *
+ * @param recyclerView The RecyclerView instance which stopped observing this adapter.
+ * @see #onAttachedToRecyclerView(RecyclerView)
+ */
+ public void onDetachedFromRecyclerView(RecyclerView recyclerView) {
+ }
+
+ /**
+ * Notify any registered observers that the data set has changed.
+ *
+ * <p>There are two different classes of data change events, item changes and structural
+ * changes. Item changes are when a single item has its data updated but no positional
+ * changes have occurred. Structural changes are when items are inserted, removed or moved
+ * within the data set.</p>
+ *
+ * <p>This event does not specify what about the data set has changed, forcing
+ * any observers to assume that all existing items and structure may no longer be valid.
+ * LayoutManagers will be forced to fully rebind and relayout all visible views.</p>
+ *
+ * <p><code>RecyclerView</code> will attempt to synthesize visible structural change events
+ * for adapters that report that they have {@link #hasStableIds() stable IDs} when
+ * this method is used. This can help for the purposes of animation and visual
+ * object persistence but individual item views will still need to be rebound
+ * and relaid out.</p>
+ *
+ * <p>If you are writing an adapter it will always be more efficient to use the more
+ * specific change events if you can. Rely on <code>notifyDataSetChanged()</code>
+ * as a last resort.</p>
+ *
+ * @see #notifyItemChanged(int)
+ * @see #notifyItemInserted(int)
+ * @see #notifyItemRemoved(int)
+ * @see #notifyItemRangeChanged(int, int)
+ * @see #notifyItemRangeInserted(int, int)
+ * @see #notifyItemRangeRemoved(int, int)
+ */
+ public final void notifyDataSetChanged() {
+ mObservable.notifyChanged();
+ }
+
+ /**
+ * Notify any registered observers that the item at <code>position</code> has changed.
+ * Equivalent to calling <code>notifyItemChanged(position, null);</code>.
+ *
+ * <p>This is an item change event, not a structural change event. It indicates that any
+ * reflection of the data at <code>position</code> is out of date and should be updated.
+ * The item at <code>position</code> retains the same identity.</p>
+ *
+ * @param position Position of the item that has changed
+ *
+ * @see #notifyItemRangeChanged(int, int)
+ */
+ public final void notifyItemChanged(int position) {
+ mObservable.notifyItemRangeChanged(position, 1);
+ }
+
+ /**
+ * Notify any registered observers that the item at <code>position</code> has changed with
+ * an optional payload object.
+ *
+ * <p>This is an item change event, not a structural change event. It indicates that any
+ * reflection of the data at <code>position</code> is out of date and should be updated.
+ * The item at <code>position</code> retains the same identity.
+ * </p>
+ *
+ * <p>
+ * Client can optionally pass a payload for partial change. These payloads will be merged
+ * and may be passed to adapter's {@link #onBindViewHolder(ViewHolder, int, List)} if the
+ * item is already represented by a ViewHolder and it will be rebound to the same
+ * ViewHolder. A notifyItemRangeChanged() with null payload will clear all existing
+ * payloads on that item and prevent future payload until
+ * {@link #onBindViewHolder(ViewHolder, int, List)} is called. Adapter should not assume
+ * that the payload will always be passed to onBindViewHolder(), e.g. when the view is not
+ * attached, the payload will be simply dropped.
+ *
+ * @param position Position of the item that has changed
+ * @param payload Optional parameter, use null to identify a "full" update
+ *
+ * @see #notifyItemRangeChanged(int, int)
+ */
+ public final void notifyItemChanged(int position, Object payload) {
+ mObservable.notifyItemRangeChanged(position, 1, payload);
+ }
+
+ /**
+ * Notify any registered observers that the <code>itemCount</code> items starting at
+ * position <code>positionStart</code> have changed.
+ * Equivalent to calling <code>notifyItemRangeChanged(position, itemCount, null);</code>.
+ *
+ * <p>This is an item change event, not a structural change event. It indicates that
+ * any reflection of the data in the given position range is out of date and should
+ * be updated. The items in the given range retain the same identity.</p>
+ *
+ * @param positionStart Position of the first item that has changed
+ * @param itemCount Number of items that have changed
+ *
+ * @see #notifyItemChanged(int)
+ */
+ public final void notifyItemRangeChanged(int positionStart, int itemCount) {
+ mObservable.notifyItemRangeChanged(positionStart, itemCount);
+ }
+
+ /**
+ * Notify any registered observers that the <code>itemCount</code> items starting at
+ * position <code>positionStart</code> have changed. An optional payload can be
+ * passed to each changed item.
+ *
+ * <p>This is an item change event, not a structural change event. It indicates that any
+ * reflection of the data in the given position range is out of date and should be updated.
+ * The items in the given range retain the same identity.
+ * </p>
+ *
+ * <p>
+ * Client can optionally pass a payload for partial change. These payloads will be merged
+ * and may be passed to adapter's {@link #onBindViewHolder(ViewHolder, int, List)} if the
+ * item is already represented by a ViewHolder and it will be rebound to the same
+ * ViewHolder. A notifyItemRangeChanged() with null payload will clear all existing
+ * payloads on that item and prevent future payload until
+ * {@link #onBindViewHolder(ViewHolder, int, List)} is called. Adapter should not assume
+ * that the payload will always be passed to onBindViewHolder(), e.g. when the view is not
+ * attached, the payload will be simply dropped.
+ *
+ * @param positionStart Position of the first item that has changed
+ * @param itemCount Number of items that have changed
+ * @param payload Optional parameter, use null to identify a "full" update
+ *
+ * @see #notifyItemChanged(int)
+ */
+ public final void notifyItemRangeChanged(int positionStart, int itemCount, Object payload) {
+ mObservable.notifyItemRangeChanged(positionStart, itemCount, payload);
+ }
+
+ /**
+ * Notify any registered observers that the item reflected at <code>position</code>
+ * has been newly inserted. The item previously at <code>position</code> is now at
+ * position <code>position + 1</code>.
+ *
+ * <p>This is a structural change event. Representations of other existing items in the
+ * data set are still considered up to date and will not be rebound, though their
+ * positions may be altered.</p>
+ *
+ * @param position Position of the newly inserted item in the data set
+ *
+ * @see #notifyItemRangeInserted(int, int)
+ */
+ public final void notifyItemInserted(int position) {
+ mObservable.notifyItemRangeInserted(position, 1);
+ }
+
+ /**
+ * Notify any registered observers that the item reflected at <code>fromPosition</code>
+ * has been moved to <code>toPosition</code>.
+ *
+ * <p>This is a structural change event. Representations of other existing items in the
+ * data set are still considered up to date and will not be rebound, though their
+ * positions may be altered.</p>
+ *
+ * @param fromPosition Previous position of the item.
+ * @param toPosition New position of the item.
+ */
+ public final void notifyItemMoved(int fromPosition, int toPosition) {
+ mObservable.notifyItemMoved(fromPosition, toPosition);
+ }
+
+ /**
+ * Notify any registered observers that the currently reflected <code>itemCount</code>
+ * items starting at <code>positionStart</code> have been newly inserted. The items
+ * previously located at <code>positionStart</code> and beyond can now be found starting
+ * at position <code>positionStart + itemCount</code>.
+ *
+ * <p>This is a structural change event. Representations of other existing items in the
+ * data set are still considered up to date and will not be rebound, though their positions
+ * may be altered.</p>
+ *
+ * @param positionStart Position of the first item that was inserted
+ * @param itemCount Number of items inserted
+ *
+ * @see #notifyItemInserted(int)
+ */
+ public final void notifyItemRangeInserted(int positionStart, int itemCount) {
+ mObservable.notifyItemRangeInserted(positionStart, itemCount);
+ }
+
+ /**
+ * Notify any registered observers that the item previously located at <code>position</code>
+ * has been removed from the data set. The items previously located at and after
+ * <code>position</code> may now be found at <code>oldPosition - 1</code>.
+ *
+ * <p>This is a structural change event. Representations of other existing items in the
+ * data set are still considered up to date and will not be rebound, though their positions
+ * may be altered.</p>
+ *
+ * @param position Position of the item that has now been removed
+ *
+ * @see #notifyItemRangeRemoved(int, int)
+ */
+ public final void notifyItemRemoved(int position) {
+ mObservable.notifyItemRangeRemoved(position, 1);
+ }
+
+ /**
+ * Notify any registered observers that the <code>itemCount</code> items previously
+ * located at <code>positionStart</code> have been removed from the data set. The items
+ * previously located at and after <code>positionStart + itemCount</code> may now be found
+ * at <code>oldPosition - itemCount</code>.
+ *
+ * <p>This is a structural change event. Representations of other existing items in the data
+ * set are still considered up to date and will not be rebound, though their positions
+ * may be altered.</p>
+ *
+ * @param positionStart Previous position of the first item that was removed
+ * @param itemCount Number of items removed from the data set
+ */
+ public final void notifyItemRangeRemoved(int positionStart, int itemCount) {
+ mObservable.notifyItemRangeRemoved(positionStart, itemCount);
+ }
+ }
+
+ void dispatchChildDetached(View child) {
+ final ViewHolder viewHolder = getChildViewHolderInt(child);
+ onChildDetachedFromWindow(child);
+ if (mAdapter != null && viewHolder != null) {
+ mAdapter.onViewDetachedFromWindow(viewHolder);
+ }
+ if (mOnChildAttachStateListeners != null) {
+ final int cnt = mOnChildAttachStateListeners.size();
+ for (int i = cnt - 1; i >= 0; i--) {
+ mOnChildAttachStateListeners.get(i).onChildViewDetachedFromWindow(child);
+ }
+ }
+ }
+
+ void dispatchChildAttached(View child) {
+ final ViewHolder viewHolder = getChildViewHolderInt(child);
+ onChildAttachedToWindow(child);
+ if (mAdapter != null && viewHolder != null) {
+ mAdapter.onViewAttachedToWindow(viewHolder);
+ }
+ if (mOnChildAttachStateListeners != null) {
+ final int cnt = mOnChildAttachStateListeners.size();
+ for (int i = cnt - 1; i >= 0; i--) {
+ mOnChildAttachStateListeners.get(i).onChildViewAttachedToWindow(child);
+ }
+ }
+ }
+
+ /**
+ * A <code>LayoutManager</code> is responsible for measuring and positioning item views
+ * within a <code>RecyclerView</code> as well as determining the policy for when to recycle
+ * item views that are no longer visible to the user. By changing the <code>LayoutManager</code>
+ * a <code>RecyclerView</code> can be used to implement a standard vertically scrolling list,
+ * a uniform grid, staggered grids, horizontally scrolling collections and more. Several stock
+ * layout managers are provided for general use.
+ * <p/>
+ * If the LayoutManager specifies a default constructor or one with the signature
+ * ({@link Context}, {@link AttributeSet}, {@code int}, {@code int}), RecyclerView will
+ * instantiate and set the LayoutManager when being inflated. Most used properties can
+ * be then obtained from {@link #getProperties(Context, AttributeSet, int, int)}. In case
+ * a LayoutManager specifies both constructors, the non-default constructor will take
+ * precedence.
+ *
+ */
+ public abstract static class LayoutManager {
+ ChildHelper mChildHelper;
+ RecyclerView mRecyclerView;
+
+ @Nullable
+ SmoothScroller mSmoothScroller;
+
+ boolean mRequestedSimpleAnimations = false;
+
+ boolean mIsAttachedToWindow = false;
+
+ boolean mAutoMeasure = false;
+
+ /**
+ * LayoutManager has its own more strict measurement cache to avoid re-measuring a child
+ * if the space that will be given to it is already larger than what it has measured before.
+ */
+ private boolean mMeasurementCacheEnabled = true;
+
+ private boolean mItemPrefetchEnabled = true;
+
+ /**
+ * Written by {@link GapWorker} when prefetches occur to track largest number of view ever
+ * requested by a {@link #collectInitialPrefetchPositions(int, LayoutPrefetchRegistry)} or
+ * {@link #collectAdjacentPrefetchPositions(int, int, State, LayoutPrefetchRegistry)} call.
+ *
+ * If expanded by a {@link #collectInitialPrefetchPositions(int, LayoutPrefetchRegistry)},
+ * will be reset upon layout to prevent initial prefetches (often large, since they're
+ * proportional to expected child count) from expanding cache permanently.
+ */
+ int mPrefetchMaxCountObserved;
+
+ /**
+ * If true, mPrefetchMaxCountObserved is only valid until next layout, and should be reset.
+ */
+ boolean mPrefetchMaxObservedInInitialPrefetch;
+
+ /**
+ * These measure specs might be the measure specs that were passed into RecyclerView's
+ * onMeasure method OR fake measure specs created by the RecyclerView.
+ * For example, when a layout is run, RecyclerView always sets these specs to be
+ * EXACTLY because a LayoutManager cannot resize RecyclerView during a layout pass.
+ * <p>
+ * Also, to be able to use the hint in unspecified measure specs, RecyclerView checks the
+ * API level and sets the size to 0 pre-M to avoid any issue that might be caused by
+ * corrupt values. Older platforms have no responsibility to provide a size if they set
+ * mode to unspecified.
+ */
+ private int mWidthMode, mHeightMode;
+ private int mWidth, mHeight;
+
+
+ /**
+ * Interface for LayoutManagers to request items to be prefetched, based on position, with
+ * specified distance from viewport, which indicates priority.
+ *
+ * @see LayoutManager#collectAdjacentPrefetchPositions(int, int, State, LayoutPrefetchRegistry)
+ * @see LayoutManager#collectInitialPrefetchPositions(int, LayoutPrefetchRegistry)
+ */
+ public interface LayoutPrefetchRegistry {
+ /**
+ * Requests an an item to be prefetched, based on position, with a specified distance,
+ * indicating priority.
+ *
+ * @param layoutPosition Position of the item to prefetch.
+ * @param pixelDistance Distance from the current viewport to the bounds of the item,
+ * must be non-negative.
+ */
+ void addPosition(int layoutPosition, int pixelDistance);
+ }
+
+ void setRecyclerView(RecyclerView recyclerView) {
+ if (recyclerView == null) {
+ mRecyclerView = null;
+ mChildHelper = null;
+ mWidth = 0;
+ mHeight = 0;
+ } else {
+ mRecyclerView = recyclerView;
+ mChildHelper = recyclerView.mChildHelper;
+ mWidth = recyclerView.getWidth();
+ mHeight = recyclerView.getHeight();
+ }
+ mWidthMode = MeasureSpec.EXACTLY;
+ mHeightMode = MeasureSpec.EXACTLY;
+ }
+
+ void setMeasureSpecs(int wSpec, int hSpec) {
+ mWidth = MeasureSpec.getSize(wSpec);
+ mWidthMode = MeasureSpec.getMode(wSpec);
+ if (mWidthMode == MeasureSpec.UNSPECIFIED && !ALLOW_SIZE_IN_UNSPECIFIED_SPEC) {
+ mWidth = 0;
+ }
+
+ mHeight = MeasureSpec.getSize(hSpec);
+ mHeightMode = MeasureSpec.getMode(hSpec);
+ if (mHeightMode == MeasureSpec.UNSPECIFIED && !ALLOW_SIZE_IN_UNSPECIFIED_SPEC) {
+ mHeight = 0;
+ }
+ }
+
+ /**
+ * Called after a layout is calculated during a measure pass when using auto-measure.
+ * <p>
+ * It simply traverses all children to calculate a bounding box then calls
+ * {@link #setMeasuredDimension(Rect, int, int)}. LayoutManagers can override that method
+ * if they need to handle the bounding box differently.
+ * <p>
+ * For example, GridLayoutManager override that method to ensure that even if a column is
+ * empty, the GridLayoutManager still measures wide enough to include it.
+ *
+ * @param widthSpec The widthSpec that was passing into RecyclerView's onMeasure
+ * @param heightSpec The heightSpec that was passing into RecyclerView's onMeasure
+ */
+ void setMeasuredDimensionFromChildren(int widthSpec, int heightSpec) {
+ final int count = getChildCount();
+ if (count == 0) {
+ mRecyclerView.defaultOnMeasure(widthSpec, heightSpec);
+ return;
+ }
+ int minX = Integer.MAX_VALUE;
+ int minY = Integer.MAX_VALUE;
+ int maxX = Integer.MIN_VALUE;
+ int maxY = Integer.MIN_VALUE;
+
+ for (int i = 0; i < count; i++) {
+ View child = getChildAt(i);
+ final Rect bounds = mRecyclerView.mTempRect;
+ getDecoratedBoundsWithMargins(child, bounds);
+ if (bounds.left < minX) {
+ minX = bounds.left;
+ }
+ if (bounds.right > maxX) {
+ maxX = bounds.right;
+ }
+ if (bounds.top < minY) {
+ minY = bounds.top;
+ }
+ if (bounds.bottom > maxY) {
+ maxY = bounds.bottom;
+ }
+ }
+ mRecyclerView.mTempRect.set(minX, minY, maxX, maxY);
+ setMeasuredDimension(mRecyclerView.mTempRect, widthSpec, heightSpec);
+ }
+
+ /**
+ * Sets the measured dimensions from the given bounding box of the children and the
+ * measurement specs that were passed into {@link RecyclerView#onMeasure(int, int)}. It is
+ * called after the RecyclerView calls
+ * {@link LayoutManager#onLayoutChildren(Recycler, State)} during a measurement pass.
+ * <p>
+ * This method should call {@link #setMeasuredDimension(int, int)}.
+ * <p>
+ * The default implementation adds the RecyclerView's padding to the given bounding box
+ * then caps the value to be within the given measurement specs.
+ * <p>
+ * This method is only called if the LayoutManager opted into the auto measurement API.
+ *
+ * @param childrenBounds The bounding box of all children
+ * @param wSpec The widthMeasureSpec that was passed into the RecyclerView.
+ * @param hSpec The heightMeasureSpec that was passed into the RecyclerView.
+ *
+ * @see #setAutoMeasureEnabled(boolean)
+ */
+ public void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec) {
+ int usedWidth = childrenBounds.width() + getPaddingLeft() + getPaddingRight();
+ int usedHeight = childrenBounds.height() + getPaddingTop() + getPaddingBottom();
+ int width = chooseSize(wSpec, usedWidth, getMinimumWidth());
+ int height = chooseSize(hSpec, usedHeight, getMinimumHeight());
+ setMeasuredDimension(width, height);
+ }
+
+ /**
+ * Calls {@code RecyclerView#requestLayout} on the underlying RecyclerView
+ */
+ public void requestLayout() {
+ if (mRecyclerView != null) {
+ mRecyclerView.requestLayout();
+ }
+ }
+
+ /**
+ * Checks if RecyclerView is in the middle of a layout or scroll and throws an
+ * {@link IllegalStateException} if it <b>is not</b>.
+ *
+ * @param message The message for the exception. Can be null.
+ * @see #assertNotInLayoutOrScroll(String)
+ */
+ public void assertInLayoutOrScroll(String message) {
+ if (mRecyclerView != null) {
+ mRecyclerView.assertInLayoutOrScroll(message);
+ }
+ }
+
+ /**
+ * Chooses a size from the given specs and parameters that is closest to the desired size
+ * and also complies with the spec.
+ *
+ * @param spec The measureSpec
+ * @param desired The preferred measurement
+ * @param min The minimum value
+ *
+ * @return A size that fits to the given specs
+ */
+ public static int chooseSize(int spec, int desired, int min) {
+ final int mode = View.MeasureSpec.getMode(spec);
+ final int size = View.MeasureSpec.getSize(spec);
+ switch (mode) {
+ case View.MeasureSpec.EXACTLY:
+ return size;
+ case View.MeasureSpec.AT_MOST:
+ return Math.min(size, Math.max(desired, min));
+ case View.MeasureSpec.UNSPECIFIED:
+ default:
+ return Math.max(desired, min);
+ }
+ }
+
+ /**
+ * Checks if RecyclerView is in the middle of a layout or scroll and throws an
+ * {@link IllegalStateException} if it <b>is</b>.
+ *
+ * @param message The message for the exception. Can be null.
+ * @see #assertInLayoutOrScroll(String)
+ */
+ public void assertNotInLayoutOrScroll(String message) {
+ if (mRecyclerView != null) {
+ mRecyclerView.assertNotInLayoutOrScroll(message);
+ }
+ }
+
+ /**
+ * Defines whether the layout should be measured by the RecyclerView or the LayoutManager
+ * wants to handle the layout measurements itself.
+ * <p>
+ * This method is usually called by the LayoutManager with value {@code true} if it wants
+ * to support WRAP_CONTENT. If you are using a public LayoutManager but want to customize
+ * the measurement logic, you can call this method with {@code false} and override
+ * {@link LayoutManager#onMeasure(int, int)} to implement your custom measurement logic.
+ * <p>
+ * AutoMeasure is a convenience mechanism for LayoutManagers to easily wrap their content or
+ * handle various specs provided by the RecyclerView's parent.
+ * It works by calling {@link LayoutManager#onLayoutChildren(Recycler, State)} during an
+ * {@link RecyclerView#onMeasure(int, int)} call, then calculating desired dimensions based
+ * on children's positions. It does this while supporting all existing animation
+ * capabilities of the RecyclerView.
+ * <p>
+ * AutoMeasure works as follows:
+ * <ol>
+ * <li>LayoutManager should call {@code setAutoMeasureEnabled(true)} to enable it. All of
+ * the framework LayoutManagers use {@code auto-measure}.</li>
+ * <li>When {@link RecyclerView#onMeasure(int, int)} is called, if the provided specs are
+ * exact, RecyclerView will only call LayoutManager's {@code onMeasure} and return without
+ * doing any layout calculation.</li>
+ * <li>If one of the layout specs is not {@code EXACT}, the RecyclerView will start the
+ * layout process in {@code onMeasure} call. It will process all pending Adapter updates and
+ * decide whether to run a predictive layout or not. If it decides to do so, it will first
+ * call {@link #onLayoutChildren(Recycler, State)} with {@link State#isPreLayout()} set to
+ * {@code true}. At this stage, {@link #getWidth()} and {@link #getHeight()} will still
+ * return the width and height of the RecyclerView as of the last layout calculation.
+ * <p>
+ * After handling the predictive case, RecyclerView will call
+ * {@link #onLayoutChildren(Recycler, State)} with {@link State#isMeasuring()} set to
+ * {@code true} and {@link State#isPreLayout()} set to {@code false}. The LayoutManager can
+ * access the measurement specs via {@link #getHeight()}, {@link #getHeightMode()},
+ * {@link #getWidth()} and {@link #getWidthMode()}.</li>
+ * <li>After the layout calculation, RecyclerView sets the measured width & height by
+ * calculating the bounding box for the children (+ RecyclerView's padding). The
+ * LayoutManagers can override {@link #setMeasuredDimension(Rect, int, int)} to choose
+ * different values. For instance, GridLayoutManager overrides this value to handle the case
+ * where if it is vertical and has 3 columns but only 2 items, it should still measure its
+ * width to fit 3 items, not 2.</li>
+ * <li>Any following on measure call to the RecyclerView will run
+ * {@link #onLayoutChildren(Recycler, State)} with {@link State#isMeasuring()} set to
+ * {@code true} and {@link State#isPreLayout()} set to {@code false}. RecyclerView will
+ * take care of which views are actually added / removed / moved / changed for animations so
+ * that the LayoutManager should not worry about them and handle each
+ * {@link #onLayoutChildren(Recycler, State)} call as if it is the last one.
+ * </li>
+ * <li>When measure is complete and RecyclerView's
+ * {@link #onLayout(boolean, int, int, int, int)} method is called, RecyclerView checks
+ * whether it already did layout calculations during the measure pass and if so, it re-uses
+ * that information. It may still decide to call {@link #onLayoutChildren(Recycler, State)}
+ * if the last measure spec was different from the final dimensions or adapter contents
+ * have changed between the measure call and the layout call.</li>
+ * <li>Finally, animations are calculated and run as usual.</li>
+ * </ol>
+ *
+ * @param enabled <code>True</code> if the Layout should be measured by the
+ * RecyclerView, <code>false</code> if the LayoutManager wants
+ * to measure itself.
+ *
+ * @see #setMeasuredDimension(Rect, int, int)
+ * @see #isAutoMeasureEnabled()
+ */
+ public void setAutoMeasureEnabled(boolean enabled) {
+ mAutoMeasure = enabled;
+ }
+
+ /**
+ * Returns whether the LayoutManager uses the automatic measurement API or not.
+ *
+ * @return <code>True</code> if the LayoutManager is measured by the RecyclerView or
+ * <code>false</code> if it measures itself.
+ *
+ * @see #setAutoMeasureEnabled(boolean)
+ */
+ public boolean isAutoMeasureEnabled() {
+ return mAutoMeasure;
+ }
+
+ /**
+ * Returns whether this LayoutManager supports automatic item animations.
+ * A LayoutManager wishing to support item animations should obey certain
+ * rules as outlined in {@link #onLayoutChildren(Recycler, State)}.
+ * The default return value is <code>false</code>, so subclasses of LayoutManager
+ * will not get predictive item animations by default.
+ *
+ * <p>Whether item animations are enabled in a RecyclerView is determined both
+ * by the return value from this method and the
+ * {@link RecyclerView#setItemAnimator(ItemAnimator) ItemAnimator} set on the
+ * RecyclerView itself. If the RecyclerView has a non-null ItemAnimator but this
+ * method returns false, then simple item animations will be enabled, in which
+ * views that are moving onto or off of the screen are simply faded in/out. If
+ * the RecyclerView has a non-null ItemAnimator and this method returns true,
+ * then there will be two calls to {@link #onLayoutChildren(Recycler, State)} to
+ * setup up the information needed to more intelligently predict where appearing
+ * and disappearing views should be animated from/to.</p>
+ *
+ * @return true if predictive item animations should be enabled, false otherwise
+ */
+ public boolean supportsPredictiveItemAnimations() {
+ return false;
+ }
+
+ /**
+ * Sets whether the LayoutManager should be queried for views outside of
+ * its viewport while the UI thread is idle between frames.
+ *
+ * <p>If enabled, the LayoutManager will be queried for items to inflate/bind in between
+ * view system traversals on devices running API 21 or greater. Default value is true.</p>
+ *
+ * <p>On platforms API level 21 and higher, the UI thread is idle between passing a frame
+ * to RenderThread and the starting up its next frame at the next VSync pulse. By
+ * prefetching out of window views in this time period, delays from inflation and view
+ * binding are much less likely to cause jank and stuttering during scrolls and flings.</p>
+ *
+ * <p>While prefetch is enabled, it will have the side effect of expanding the effective
+ * size of the View cache to hold prefetched views.</p>
+ *
+ * @param enabled <code>True</code> if items should be prefetched in between traversals.
+ *
+ * @see #isItemPrefetchEnabled()
+ */
+ public final void setItemPrefetchEnabled(boolean enabled) {
+ if (enabled != mItemPrefetchEnabled) {
+ mItemPrefetchEnabled = enabled;
+ mPrefetchMaxCountObserved = 0;
+ if (mRecyclerView != null) {
+ mRecyclerView.mRecycler.updateViewCacheSize();
+ }
+ }
+ }
+
+ /**
+ * Sets whether the LayoutManager should be queried for views outside of
+ * its viewport while the UI thread is idle between frames.
+ *
+ * @see #setItemPrefetchEnabled(boolean)
+ *
+ * @return true if item prefetch is enabled, false otherwise
+ */
+ public final boolean isItemPrefetchEnabled() {
+ return mItemPrefetchEnabled;
+ }
+
+ /**
+ * Gather all positions from the LayoutManager to be prefetched, given specified momentum.
+ *
+ * <p>If item prefetch is enabled, this method is called in between traversals to gather
+ * which positions the LayoutManager will soon need, given upcoming movement in subsequent
+ * traversals.</p>
+ *
+ * <p>The LayoutManager should call {@link LayoutPrefetchRegistry#addPosition(int, int)} for
+ * each item to be prepared, and these positions will have their ViewHolders created and
+ * bound, if there is sufficient time available, in advance of being needed by a
+ * scroll or layout.</p>
+ *
+ * @param dx X movement component.
+ * @param dy Y movement component.
+ * @param state State of RecyclerView
+ * @param layoutPrefetchRegistry PrefetchRegistry to add prefetch entries into.
+ *
+ * @see #isItemPrefetchEnabled()
+ * @see #collectInitialPrefetchPositions(int, LayoutPrefetchRegistry)
+ */
+ public void collectAdjacentPrefetchPositions(int dx, int dy, State state,
+ LayoutPrefetchRegistry layoutPrefetchRegistry) {}
+
+ /**
+ * Gather all positions from the LayoutManager to be prefetched in preperation for its
+ * RecyclerView to come on screen, due to the movement of another, containing RecyclerView.
+ *
+ * <p>This method is only called when a RecyclerView is nested in another RecyclerView.</p>
+ *
+ * <p>If item prefetch is enabled for this LayoutManager, as well in another containing
+ * LayoutManager, this method is called in between draw traversals to gather
+ * which positions this LayoutManager will first need, once it appears on the screen.</p>
+ *
+ * <p>For example, if this LayoutManager represents a horizontally scrolling list within a
+ * vertically scrolling LayoutManager, this method would be called when the horizontal list
+ * is about to come onscreen.</p>
+ *
+ * <p>The LayoutManager should call {@link LayoutPrefetchRegistry#addPosition(int, int)} for
+ * each item to be prepared, and these positions will have their ViewHolders created and
+ * bound, if there is sufficient time available, in advance of being needed by a
+ * scroll or layout.</p>
+ *
+ * @param adapterItemCount number of items in the associated adapter.
+ * @param layoutPrefetchRegistry PrefetchRegistry to add prefetch entries into.
+ *
+ * @see #isItemPrefetchEnabled()
+ * @see #collectAdjacentPrefetchPositions(int, int, State, LayoutPrefetchRegistry)
+ */
+ public void collectInitialPrefetchPositions(int adapterItemCount,
+ LayoutPrefetchRegistry layoutPrefetchRegistry) {}
+
+ void dispatchAttachedToWindow(RecyclerView view) {
+ mIsAttachedToWindow = true;
+ onAttachedToWindow(view);
+ }
+
+ void dispatchDetachedFromWindow(RecyclerView view, Recycler recycler) {
+ mIsAttachedToWindow = false;
+ onDetachedFromWindow(view, recycler);
+ }
+
+ /**
+ * Returns whether LayoutManager is currently attached to a RecyclerView which is attached
+ * to a window.
+ *
+ * @return True if this LayoutManager is controlling a RecyclerView and the RecyclerView
+ * is attached to window.
+ */
+ public boolean isAttachedToWindow() {
+ return mIsAttachedToWindow;
+ }
+
+ /**
+ * Causes the Runnable to execute on the next animation time step.
+ * The runnable will be run on the user interface thread.
+ * <p>
+ * Calling this method when LayoutManager is not attached to a RecyclerView has no effect.
+ *
+ * @param action The Runnable that will be executed.
+ *
+ * @see #removeCallbacks
+ */
+ public void postOnAnimation(Runnable action) {
+ if (mRecyclerView != null) {
+ mRecyclerView.postOnAnimation(action);
+ }
+ }
+
+ /**
+ * Removes the specified Runnable from the message queue.
+ * <p>
+ * Calling this method when LayoutManager is not attached to a RecyclerView has no effect.
+ *
+ * @param action The Runnable to remove from the message handling queue
+ *
+ * @return true if RecyclerView could ask the Handler to remove the Runnable,
+ * false otherwise. When the returned value is true, the Runnable
+ * may or may not have been actually removed from the message queue
+ * (for instance, if the Runnable was not in the queue already.)
+ *
+ * @see #postOnAnimation
+ */
+ public boolean removeCallbacks(Runnable action) {
+ if (mRecyclerView != null) {
+ return mRecyclerView.removeCallbacks(action);
+ }
+ return false;
+ }
+ /**
+ * Called when this LayoutManager is both attached to a RecyclerView and that RecyclerView
+ * is attached to a window.
+ * <p>
+ * If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not
+ * call {@link #onLayoutChildren(Recycler, State)} if nothing has changed and a layout was
+ * not requested on the RecyclerView while it was detached.
+ * <p>
+ * Subclass implementations should always call through to the superclass implementation.
+ *
+ * @param view The RecyclerView this LayoutManager is bound to
+ *
+ * @see #onDetachedFromWindow(RecyclerView, Recycler)
+ */
+ @CallSuper
+ public void onAttachedToWindow(RecyclerView view) {
+ }
+
+ /**
+ * @deprecated
+ * override {@link #onDetachedFromWindow(RecyclerView, Recycler)}
+ */
+ @Deprecated
+ public void onDetachedFromWindow(RecyclerView view) {
+
+ }
+
+ /**
+ * Called when this LayoutManager is detached from its parent RecyclerView or when
+ * its parent RecyclerView is detached from its window.
+ * <p>
+ * LayoutManager should clear all of its View references as another LayoutManager might be
+ * assigned to the RecyclerView.
+ * <p>
+ * If the RecyclerView is re-attached with the same LayoutManager and Adapter, it may not
+ * call {@link #onLayoutChildren(Recycler, State)} if nothing has changed and a layout was
+ * not requested on the RecyclerView while it was detached.
+ * <p>
+ * If your LayoutManager has View references that it cleans in on-detach, it should also
+ * call {@link RecyclerView#requestLayout()} to ensure that it is re-laid out when
+ * RecyclerView is re-attached.
+ * <p>
+ * Subclass implementations should always call through to the superclass implementation.
+ *
+ * @param view The RecyclerView this LayoutManager is bound to
+ * @param recycler The recycler to use if you prefer to recycle your children instead of
+ * keeping them around.
+ *
+ * @see #onAttachedToWindow(RecyclerView)
+ */
+ @CallSuper
+ public void onDetachedFromWindow(RecyclerView view, Recycler recycler) {
+ onDetachedFromWindow(view);
+ }
+
+ /**
+ * Check if the RecyclerView is configured to clip child views to its padding.
+ *
+ * @return true if this RecyclerView clips children to its padding, false otherwise
+ */
+ public boolean getClipToPadding() {
+ return mRecyclerView != null && mRecyclerView.mClipToPadding;
+ }
+
+ /**
+ * Lay out all relevant child views from the given adapter.
+ *
+ * The LayoutManager is in charge of the behavior of item animations. By default,
+ * RecyclerView has a non-null {@link #getItemAnimator() ItemAnimator}, and simple
+ * item animations are enabled. This means that add/remove operations on the
+ * adapter will result in animations to add new or appearing items, removed or
+ * disappearing items, and moved items. If a LayoutManager returns false from
+ * {@link #supportsPredictiveItemAnimations()}, which is the default, and runs a
+ * normal layout operation during {@link #onLayoutChildren(Recycler, State)}, the
+ * RecyclerView will have enough information to run those animations in a simple
+ * way. For example, the default ItemAnimator, {@link DefaultItemAnimator}, will
+ * simply fade views in and out, whether they are actually added/removed or whether
+ * they are moved on or off the screen due to other add/remove operations.
+ *
+ * <p>A LayoutManager wanting a better item animation experience, where items can be
+ * animated onto and off of the screen according to where the items exist when they
+ * are not on screen, then the LayoutManager should return true from
+ * {@link #supportsPredictiveItemAnimations()} and add additional logic to
+ * {@link #onLayoutChildren(Recycler, State)}. Supporting predictive animations
+ * means that {@link #onLayoutChildren(Recycler, State)} will be called twice;
+ * once as a "pre" layout step to determine where items would have been prior to
+ * a real layout, and again to do the "real" layout. In the pre-layout phase,
+ * items will remember their pre-layout positions to allow them to be laid out
+ * appropriately. Also, {@link LayoutParams#isItemRemoved() removed} items will
+ * be returned from the scrap to help determine correct placement of other items.
+ * These removed items should not be added to the child list, but should be used
+ * to help calculate correct positioning of other views, including views that
+ * were not previously onscreen (referred to as APPEARING views), but whose
+ * pre-layout offscreen position can be determined given the extra
+ * information about the pre-layout removed views.</p>
+ *
+ * <p>The second layout pass is the real layout in which only non-removed views
+ * will be used. The only additional requirement during this pass is, if
+ * {@link #supportsPredictiveItemAnimations()} returns true, to note which
+ * views exist in the child list prior to layout and which are not there after
+ * layout (referred to as DISAPPEARING views), and to position/layout those views
+ * appropriately, without regard to the actual bounds of the RecyclerView. This allows
+ * the animation system to know the location to which to animate these disappearing
+ * views.</p>
+ *
+ * <p>The default LayoutManager implementations for RecyclerView handle all of these
+ * requirements for animations already. Clients of RecyclerView can either use one
+ * of these layout managers directly or look at their implementations of
+ * onLayoutChildren() to see how they account for the APPEARING and
+ * DISAPPEARING views.</p>
+ *
+ * @param recycler Recycler to use for fetching potentially cached views for a
+ * position
+ * @param state Transient state of RecyclerView
+ */
+ public void onLayoutChildren(Recycler recycler, State state) {
+ Log.e(TAG, "You must override onLayoutChildren(Recycler recycler, State state) ");
+ }
+
+ /**
+ * Called after a full layout calculation is finished. The layout calculation may include
+ * multiple {@link #onLayoutChildren(Recycler, State)} calls due to animations or
+ * layout measurement but it will include only one {@link #onLayoutCompleted(State)} call.
+ * This method will be called at the end of {@link View#layout(int, int, int, int)} call.
+ * <p>
+ * This is a good place for the LayoutManager to do some cleanup like pending scroll
+ * position, saved state etc.
+ *
+ * @param state Transient state of RecyclerView
+ */
+ public void onLayoutCompleted(State state) {
+ }
+
+ /**
+ * Create a default <code>LayoutParams</code> object for a child of the RecyclerView.
+ *
+ * <p>LayoutManagers will often want to use a custom <code>LayoutParams</code> type
+ * to store extra information specific to the layout. Client code should subclass
+ * {@link RecyclerView.LayoutParams} for this purpose.</p>
+ *
+ * <p><em>Important:</em> if you use your own custom <code>LayoutParams</code> type
+ * you must also override
+ * {@link #checkLayoutParams(LayoutParams)},
+ * {@link #generateLayoutParams(android.view.ViewGroup.LayoutParams)} and
+ * {@link #generateLayoutParams(android.content.Context, android.util.AttributeSet)}.</p>
+ *
+ * @return A new LayoutParams for a child view
+ */
+ public abstract LayoutParams generateDefaultLayoutParams();
+
+ /**
+ * Determines the validity of the supplied LayoutParams object.
+ *
+ * <p>This should check to make sure that the object is of the correct type
+ * and all values are within acceptable ranges. The default implementation
+ * returns <code>true</code> for non-null params.</p>
+ *
+ * @param lp LayoutParams object to check
+ * @return true if this LayoutParams object is valid, false otherwise
+ */
+ public boolean checkLayoutParams(LayoutParams lp) {
+ return lp != null;
+ }
+
+ /**
+ * Create a LayoutParams object suitable for this LayoutManager, copying relevant
+ * values from the supplied LayoutParams object if possible.
+ *
+ * <p><em>Important:</em> if you use your own custom <code>LayoutParams</code> type
+ * you must also override
+ * {@link #checkLayoutParams(LayoutParams)},
+ * {@link #generateLayoutParams(android.view.ViewGroup.LayoutParams)} and
+ * {@link #generateLayoutParams(android.content.Context, android.util.AttributeSet)}.</p>
+ *
+ * @param lp Source LayoutParams object to copy values from
+ * @return a new LayoutParams object
+ */
+ public LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp) {
+ if (lp instanceof LayoutParams) {
+ return new LayoutParams((LayoutParams) lp);
+ } else if (lp instanceof MarginLayoutParams) {
+ return new LayoutParams((MarginLayoutParams) lp);
+ } else {
+ return new LayoutParams(lp);
+ }
+ }
+
+ /**
+ * Create a LayoutParams object suitable for this LayoutManager from
+ * an inflated layout resource.
+ *
+ * <p><em>Important:</em> if you use your own custom <code>LayoutParams</code> type
+ * you must also override
+ * {@link #checkLayoutParams(LayoutParams)},
+ * {@link #generateLayoutParams(android.view.ViewGroup.LayoutParams)} and
+ * {@link #generateLayoutParams(android.content.Context, android.util.AttributeSet)}.</p>
+ *
+ * @param c Context for obtaining styled attributes
+ * @param attrs AttributeSet describing the supplied arguments
+ * @return a new LayoutParams object
+ */
+ public LayoutParams generateLayoutParams(Context c, AttributeSet attrs) {
+ return new LayoutParams(c, attrs);
+ }
+
+ /**
+ * Scroll horizontally by dx pixels in screen coordinates and return the distance traveled.
+ * The default implementation does nothing and returns 0.
+ *
+ * @param dx distance to scroll by in pixels. X increases as scroll position
+ * approaches the right.
+ * @param recycler Recycler to use for fetching potentially cached views for a
+ * position
+ * @param state Transient state of RecyclerView
+ * @return The actual distance scrolled. The return value will be negative if dx was
+ * negative and scrolling proceeeded in that direction.
+ * <code>Math.abs(result)</code> may be less than dx if a boundary was reached.
+ */
+ public int scrollHorizontallyBy(int dx, Recycler recycler, State state) {
+ return 0;
+ }
+
+ /**
+ * Scroll vertically by dy pixels in screen coordinates and return the distance traveled.
+ * The default implementation does nothing and returns 0.
+ *
+ * @param dy distance to scroll in pixels. Y increases as scroll position
+ * approaches the bottom.
+ * @param recycler Recycler to use for fetching potentially cached views for a
+ * position
+ * @param state Transient state of RecyclerView
+ * @return The actual distance scrolled. The return value will be negative if dy was
+ * negative and scrolling proceeeded in that direction.
+ * <code>Math.abs(result)</code> may be less than dy if a boundary was reached.
+ */
+ public int scrollVerticallyBy(int dy, Recycler recycler, State state) {
+ return 0;
+ }
+
+ /**
+ * Query if horizontal scrolling is currently supported. The default implementation
+ * returns false.
+ *
+ * @return True if this LayoutManager can scroll the current contents horizontally
+ */
+ public boolean canScrollHorizontally() {
+ return false;
+ }
+
+ /**
+ * Query if vertical scrolling is currently supported. The default implementation
+ * returns false.
+ *
+ * @return True if this LayoutManager can scroll the current contents vertically
+ */
+ public boolean canScrollVertically() {
+ return false;
+ }
+
+ /**
+ * Scroll to the specified adapter position.
+ *
+ * Actual position of the item on the screen depends on the LayoutManager implementation.
+ * @param position Scroll to this adapter position.
+ */
+ public void scrollToPosition(int position) {
+ if (DEBUG) {
+ Log.e(TAG, "You MUST implement scrollToPosition. It will soon become abstract");
+ }
+ }
+
+ /**
+ * <p>Smooth scroll to the specified adapter position.</p>
+ * <p>To support smooth scrolling, override this method, create your {@link SmoothScroller}
+ * instance and call {@link #startSmoothScroll(SmoothScroller)}.
+ * </p>
+ * @param recyclerView The RecyclerView to which this layout manager is attached
+ * @param state Current State of RecyclerView
+ * @param position Scroll to this adapter position.
+ */
+ public void smoothScrollToPosition(RecyclerView recyclerView, State state,
+ int position) {
+ Log.e(TAG, "You must override smoothScrollToPosition to support smooth scrolling");
+ }
+
+ /**
+ * <p>Starts a smooth scroll using the provided SmoothScroller.</p>
+ * <p>Calling this method will cancel any previous smooth scroll request.</p>
+ * @param smoothScroller Instance which defines how smooth scroll should be animated
+ */
+ public void startSmoothScroll(SmoothScroller smoothScroller) {
+ if (mSmoothScroller != null && smoothScroller != mSmoothScroller
+ && mSmoothScroller.isRunning()) {
+ mSmoothScroller.stop();
+ }
+ mSmoothScroller = smoothScroller;
+ mSmoothScroller.start(mRecyclerView, this);
+ }
+
+ /**
+ * @return true if RecycylerView is currently in the state of smooth scrolling.
+ */
+ public boolean isSmoothScrolling() {
+ return mSmoothScroller != null && mSmoothScroller.isRunning();
+ }
+
+
+ /**
+ * Returns the resolved layout direction for this RecyclerView.
+ *
+ * @return {@link android.view.View#LAYOUT_DIRECTION_RTL} if the layout
+ * direction is RTL or returns
+ * {@link android.view.View#LAYOUT_DIRECTION_LTR} if the layout direction
+ * is not RTL.
+ */
+ public int getLayoutDirection() {
+ return mRecyclerView.getLayoutDirection();
+ }
+
+ /**
+ * Ends all animations on the view created by the {@link ItemAnimator}.
+ *
+ * @param view The View for which the animations should be ended.
+ * @see RecyclerView.ItemAnimator#endAnimations()
+ */
+ public void endAnimation(View view) {
+ if (mRecyclerView.mItemAnimator != null) {
+ mRecyclerView.mItemAnimator.endAnimation(getChildViewHolderInt(view));
+ }
+ }
+
+ /**
+ * To be called only during {@link #onLayoutChildren(Recycler, State)} to add a view
+ * to the layout that is known to be going away, either because it has been
+ * {@link Adapter#notifyItemRemoved(int) removed} or because it is actually not in the
+ * visible portion of the container but is being laid out in order to inform RecyclerView
+ * in how to animate the item out of view.
+ * <p>
+ * Views added via this method are going to be invisible to LayoutManager after the
+ * dispatchLayout pass is complete. They cannot be retrieved via {@link #getChildAt(int)}
+ * or won't be included in {@link #getChildCount()} method.
+ *
+ * @param child View to add and then remove with animation.
+ */
+ public void addDisappearingView(View child) {
+ addDisappearingView(child, -1);
+ }
+
+ /**
+ * To be called only during {@link #onLayoutChildren(Recycler, State)} to add a view
+ * to the layout that is known to be going away, either because it has been
+ * {@link Adapter#notifyItemRemoved(int) removed} or because it is actually not in the
+ * visible portion of the container but is being laid out in order to inform RecyclerView
+ * in how to animate the item out of view.
+ * <p>
+ * Views added via this method are going to be invisible to LayoutManager after the
+ * dispatchLayout pass is complete. They cannot be retrieved via {@link #getChildAt(int)}
+ * or won't be included in {@link #getChildCount()} method.
+ *
+ * @param child View to add and then remove with animation.
+ * @param index Index of the view.
+ */
+ public void addDisappearingView(View child, int index) {
+ addViewInt(child, index, true);
+ }
+
+ /**
+ * Add a view to the currently attached RecyclerView if needed. LayoutManagers should
+ * use this method to add views obtained from a {@link Recycler} using
+ * {@link Recycler#getViewForPosition(int)}.
+ *
+ * @param child View to add
+ */
+ public void addView(View child) {
+ addView(child, -1);
+ }
+
+ /**
+ * Add a view to the currently attached RecyclerView if needed. LayoutManagers should
+ * use this method to add views obtained from a {@link Recycler} using
+ * {@link Recycler#getViewForPosition(int)}.
+ *
+ * @param child View to add
+ * @param index Index to add child at
+ */
+ public void addView(View child, int index) {
+ addViewInt(child, index, false);
+ }
+
+ private void addViewInt(View child, int index, boolean disappearing) {
+ final ViewHolder holder = getChildViewHolderInt(child);
+ if (disappearing || holder.isRemoved()) {
+ // these views will be hidden at the end of the layout pass.
+ mRecyclerView.mViewInfoStore.addToDisappearedInLayout(holder);
+ } else {
+ // This may look like unnecessary but may happen if layout manager supports
+ // predictive layouts and adapter removed then re-added the same item.
+ // In this case, added version will be visible in the post layout (because add is
+ // deferred) but RV will still bind it to the same View.
+ // So if a View re-appears in post layout pass, remove it from disappearing list.
+ mRecyclerView.mViewInfoStore.removeFromDisappearedInLayout(holder);
+ }
+ final LayoutParams lp = (LayoutParams) child.getLayoutParams();
+ if (holder.wasReturnedFromScrap() || holder.isScrap()) {
+ if (holder.isScrap()) {
+ holder.unScrap();
+ } else {
+ holder.clearReturnedFromScrapFlag();
+ }
+ mChildHelper.attachViewToParent(child, index, child.getLayoutParams(), false);
+ if (DISPATCH_TEMP_DETACH) {
+ child.dispatchFinishTemporaryDetach();
+ }
+ } else if (child.getParent() == mRecyclerView) { // it was not a scrap but a valid child
+ // ensure in correct position
+ int currentIndex = mChildHelper.indexOfChild(child);
+ if (index == -1) {
+ index = mChildHelper.getChildCount();
+ }
+ if (currentIndex == -1) {
+ throw new IllegalStateException("Added View has RecyclerView as parent but"
+ + " view is not a real child. Unfiltered index:"
+ + mRecyclerView.indexOfChild(child));
+ }
+ if (currentIndex != index) {
+ mRecyclerView.mLayout.moveView(currentIndex, index);
+ }
+ } else {
+ mChildHelper.addView(child, index, false);
+ lp.mInsetsDirty = true;
+ if (mSmoothScroller != null && mSmoothScroller.isRunning()) {
+ mSmoothScroller.onChildAttachedToWindow(child);
+ }
+ }
+ if (lp.mPendingInvalidate) {
+ if (DEBUG) {
+ Log.d(TAG, "consuming pending invalidate on child " + lp.mViewHolder);
+ }
+ holder.itemView.invalidate();
+ lp.mPendingInvalidate = false;
+ }
+ }
+
+ /**
+ * Remove a view from the currently attached RecyclerView if needed. LayoutManagers should
+ * use this method to completely remove a child view that is no longer needed.
+ * LayoutManagers should strongly consider recycling removed views using
+ * {@link Recycler#recycleView(android.view.View)}.
+ *
+ * @param child View to remove
+ */
+ public void removeView(View child) {
+ mChildHelper.removeView(child);
+ }
+
+ /**
+ * Remove a view from the currently attached RecyclerView if needed. LayoutManagers should
+ * use this method to completely remove a child view that is no longer needed.
+ * LayoutManagers should strongly consider recycling removed views using
+ * {@link Recycler#recycleView(android.view.View)}.
+ *
+ * @param index Index of the child view to remove
+ */
+ public void removeViewAt(int index) {
+ final View child = getChildAt(index);
+ if (child != null) {
+ mChildHelper.removeViewAt(index);
+ }
+ }
+
+ /**
+ * Remove all views from the currently attached RecyclerView. This will not recycle
+ * any of the affected views; the LayoutManager is responsible for doing so if desired.
+ */
+ public void removeAllViews() {
+ // Only remove non-animating views
+ final int childCount = getChildCount();
+ for (int i = childCount - 1; i >= 0; i--) {
+ mChildHelper.removeViewAt(i);
+ }
+ }
+
+ /**
+ * Returns offset of the RecyclerView's text baseline from the its top boundary.
+ *
+ * @return The offset of the RecyclerView's text baseline from the its top boundary; -1 if
+ * there is no baseline.
+ */
+ public int getBaseline() {
+ return -1;
+ }
+
+ /**
+ * Returns the adapter position of the item represented by the given View. This does not
+ * contain any adapter changes that might have happened after the last layout.
+ *
+ * @param view The view to query
+ * @return The adapter position of the item which is rendered by this View.
+ */
+ public int getPosition(View view) {
+ return ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewLayoutPosition();
+ }
+
+ /**
+ * Returns the View type defined by the adapter.
+ *
+ * @param view The view to query
+ * @return The type of the view assigned by the adapter.
+ */
+ public int getItemViewType(View view) {
+ return getChildViewHolderInt(view).getItemViewType();
+ }
+
+ /**
+ * Traverses the ancestors of the given view and returns the item view that contains it
+ * and also a direct child of the LayoutManager.
+ * <p>
+ * Note that this method may return null if the view is a child of the RecyclerView but
+ * not a child of the LayoutManager (e.g. running a disappear animation).
+ *
+ * @param view The view that is a descendant of the LayoutManager.
+ *
+ * @return The direct child of the LayoutManager which contains the given view or null if
+ * the provided view is not a descendant of this LayoutManager.
+ *
+ * @see RecyclerView#getChildViewHolder(View)
+ * @see RecyclerView#findContainingViewHolder(View)
+ */
+ @Nullable
+ public View findContainingItemView(View view) {
+ if (mRecyclerView == null) {
+ return null;
+ }
+ View found = mRecyclerView.findContainingItemView(view);
+ if (found == null) {
+ return null;
+ }
+ if (mChildHelper.isHidden(found)) {
+ return null;
+ }
+ return found;
+ }
+
+ /**
+ * Finds the view which represents the given adapter position.
+ * <p>
+ * This method traverses each child since it has no information about child order.
+ * Override this method to improve performance if your LayoutManager keeps data about
+ * child views.
+ * <p>
+ * If a view is ignored via {@link #ignoreView(View)}, it is also ignored by this method.
+ *
+ * @param position Position of the item in adapter
+ * @return The child view that represents the given position or null if the position is not
+ * laid out
+ */
+ public View findViewByPosition(int position) {
+ final int childCount = getChildCount();
+ for (int i = 0; i < childCount; i++) {
+ View child = getChildAt(i);
+ ViewHolder vh = getChildViewHolderInt(child);
+ if (vh == null) {
+ continue;
+ }
+ if (vh.getLayoutPosition() == position && !vh.shouldIgnore()
+ && (mRecyclerView.mState.isPreLayout() || !vh.isRemoved())) {
+ return child;
+ }
+ }
+ return null;
+ }
+
+ /**
+ * Temporarily detach a child view.
+ *
+ * <p>LayoutManagers may want to perform a lightweight detach operation to rearrange
+ * views currently attached to the RecyclerView. Generally LayoutManager implementations
+ * will want to use {@link #detachAndScrapView(android.view.View, RecyclerView.Recycler)}
+ * so that the detached view may be rebound and reused.</p>
+ *
+ * <p>If a LayoutManager uses this method to detach a view, it <em>must</em>
+ * {@link #attachView(android.view.View, int, RecyclerView.LayoutParams) reattach}
+ * or {@link #removeDetachedView(android.view.View) fully remove} the detached view
+ * before the LayoutManager entry point method called by RecyclerView returns.</p>
+ *
+ * @param child Child to detach
+ */
+ public void detachView(View child) {
+ final int ind = mChildHelper.indexOfChild(child);
+ if (ind >= 0) {
+ detachViewInternal(ind, child);
+ }
+ }
+
+ /**
+ * Temporarily detach a child view.
+ *
+ * <p>LayoutManagers may want to perform a lightweight detach operation to rearrange
+ * views currently attached to the RecyclerView. Generally LayoutManager implementations
+ * will want to use {@link #detachAndScrapView(android.view.View, RecyclerView.Recycler)}
+ * so that the detached view may be rebound and reused.</p>
+ *
+ * <p>If a LayoutManager uses this method to detach a view, it <em>must</em>
+ * {@link #attachView(android.view.View, int, RecyclerView.LayoutParams) reattach}
+ * or {@link #removeDetachedView(android.view.View) fully remove} the detached view
+ * before the LayoutManager entry point method called by RecyclerView returns.</p>
+ *
+ * @param index Index of the child to detach
+ */
+ public void detachViewAt(int index) {
+ detachViewInternal(index, getChildAt(index));
+ }
+
+ private void detachViewInternal(int index, View view) {
+ if (DISPATCH_TEMP_DETACH) {
+ view.dispatchStartTemporaryDetach();
+ }
+ mChildHelper.detachViewFromParent(index);
+ }
+
+ /**
+ * Reattach a previously {@link #detachView(android.view.View) detached} view.
+ * This method should not be used to reattach views that were previously
+ * {@link #detachAndScrapView(android.view.View, RecyclerView.Recycler)} scrapped}.
+ *
+ * @param child Child to reattach
+ * @param index Intended child index for child
+ * @param lp LayoutParams for child
+ */
+ public void attachView(View child, int index, LayoutParams lp) {
+ ViewHolder vh = getChildViewHolderInt(child);
+ if (vh.isRemoved()) {
+ mRecyclerView.mViewInfoStore.addToDisappearedInLayout(vh);
+ } else {
+ mRecyclerView.mViewInfoStore.removeFromDisappearedInLayout(vh);
+ }
+ mChildHelper.attachViewToParent(child, index, lp, vh.isRemoved());
+ if (DISPATCH_TEMP_DETACH) {
+ child.dispatchFinishTemporaryDetach();
+ }
+ }
+
+ /**
+ * Reattach a previously {@link #detachView(android.view.View) detached} view.
+ * This method should not be used to reattach views that were previously
+ * {@link #detachAndScrapView(android.view.View, RecyclerView.Recycler)} scrapped}.
+ *
+ * @param child Child to reattach
+ * @param index Intended child index for child
+ */
+ public void attachView(View child, int index) {
+ attachView(child, index, (LayoutParams) child.getLayoutParams());
+ }
+
+ /**
+ * Reattach a previously {@link #detachView(android.view.View) detached} view.
+ * This method should not be used to reattach views that were previously
+ * {@link #detachAndScrapView(android.view.View, RecyclerView.Recycler)} scrapped}.
+ *
+ * @param child Child to reattach
+ */
+ public void attachView(View child) {
+ attachView(child, -1);
+ }
+
+ /**
+ * Finish removing a view that was previously temporarily
+ * {@link #detachView(android.view.View) detached}.
+ *
+ * @param child Detached child to remove
+ */
+ public void removeDetachedView(View child) {
+ mRecyclerView.removeDetachedView(child, false);
+ }
+
+ /**
+ * Moves a View from one position to another.
+ *
+ * @param fromIndex The View's initial index
+ * @param toIndex The View's target index
+ */
+ public void moveView(int fromIndex, int toIndex) {
+ View view = getChildAt(fromIndex);
+ if (view == null) {
+ throw new IllegalArgumentException("Cannot move a child from non-existing index:"
+ + fromIndex);
+ }
+ detachViewAt(fromIndex);
+ attachView(view, toIndex);
+ }
+
+ /**
+ * Detach a child view and add it to a {@link Recycler Recycler's} scrap heap.
+ *
+ * <p>Scrapping a view allows it to be rebound and reused to show updated or
+ * different data.</p>
+ *
+ * @param child Child to detach and scrap
+ * @param recycler Recycler to deposit the new scrap view into
+ */
+ public void detachAndScrapView(View child, Recycler recycler) {
+ int index = mChildHelper.indexOfChild(child);
+ scrapOrRecycleView(recycler, index, child);
+ }
+
+ /**
+ * Detach a child view and add it to a {@link Recycler Recycler's} scrap heap.
+ *
+ * <p>Scrapping a view allows it to be rebound and reused to show updated or
+ * different data.</p>
+ *
+ * @param index Index of child to detach and scrap
+ * @param recycler Recycler to deposit the new scrap view into
+ */
+ public void detachAndScrapViewAt(int index, Recycler recycler) {
+ final View child = getChildAt(index);
+ scrapOrRecycleView(recycler, index, child);
+ }
+
+ /**
+ * Remove a child view and recycle it using the given Recycler.
+ *
+ * @param child Child to remove and recycle
+ * @param recycler Recycler to use to recycle child
+ */
+ public void removeAndRecycleView(View child, Recycler recycler) {
+ removeView(child);
+ recycler.recycleView(child);
+ }
+
+ /**
+ * Remove a child view and recycle it using the given Recycler.
+ *
+ * @param index Index of child to remove and recycle
+ * @param recycler Recycler to use to recycle child
+ */
+ public void removeAndRecycleViewAt(int index, Recycler recycler) {
+ final View view = getChildAt(index);
+ removeViewAt(index);
+ recycler.recycleView(view);
+ }
+
+ /**
+ * Return the current number of child views attached to the parent RecyclerView.
+ * This does not include child views that were temporarily detached and/or scrapped.
+ *
+ * @return Number of attached children
+ */
+ public int getChildCount() {
+ return mChildHelper != null ? mChildHelper.getChildCount() : 0;
+ }
+
+ /**
+ * Return the child view at the given index
+ * @param index Index of child to return
+ * @return Child view at index
+ */
+ public View getChildAt(int index) {
+ return mChildHelper != null ? mChildHelper.getChildAt(index) : null;
+ }
+
+ /**
+ * Return the width measurement spec mode of the RecyclerView.
+ * <p>
+ * This value is set only if the LayoutManager opts into the auto measure api via
+ * {@link #setAutoMeasureEnabled(boolean)}.
+ * <p>
+ * When RecyclerView is running a layout, this value is always set to
+ * {@link View.MeasureSpec#EXACTLY} even if it was measured with a different spec mode.
+ *
+ * @return Width measure spec mode.
+ *
+ * @see View.MeasureSpec#getMode(int)
+ * @see View#onMeasure(int, int)
+ */
+ public int getWidthMode() {
+ return mWidthMode;
+ }
+
+ /**
+ * Return the height measurement spec mode of the RecyclerView.
+ * <p>
+ * This value is set only if the LayoutManager opts into the auto measure api via
+ * {@link #setAutoMeasureEnabled(boolean)}.
+ * <p>
+ * When RecyclerView is running a layout, this value is always set to
+ * {@link View.MeasureSpec#EXACTLY} even if it was measured with a different spec mode.
+ *
+ * @return Height measure spec mode.
+ *
+ * @see View.MeasureSpec#getMode(int)
+ * @see View#onMeasure(int, int)
+ */
+ public int getHeightMode() {
+ return mHeightMode;
+ }
+
+ /**
+ * Return the width of the parent RecyclerView
+ *
+ * @return Width in pixels
+ */
+ public int getWidth() {
+ return mWidth;
+ }
+
+ /**
+ * Return the height of the parent RecyclerView
+ *
+ * @return Height in pixels
+ */
+ public int getHeight() {
+ return mHeight;
+ }
+
+ /**
+ * Return the left padding of the parent RecyclerView
+ *
+ * @return Padding in pixels
+ */
+ public int getPaddingLeft() {
+ return mRecyclerView != null ? mRecyclerView.getPaddingLeft() : 0;
+ }
+
+ /**
+ * Return the top padding of the parent RecyclerView
+ *
+ * @return Padding in pixels
+ */
+ public int getPaddingTop() {
+ return mRecyclerView != null ? mRecyclerView.getPaddingTop() : 0;
+ }
+
+ /**
+ * Return the right padding of the parent RecyclerView
+ *
+ * @return Padding in pixels
+ */
+ public int getPaddingRight() {
+ return mRecyclerView != null ? mRecyclerView.getPaddingRight() : 0;
+ }
+
+ /**
+ * Return the bottom padding of the parent RecyclerView
+ *
+ * @return Padding in pixels
+ */
+ public int getPaddingBottom() {
+ return mRecyclerView != null ? mRecyclerView.getPaddingBottom() : 0;
+ }
+
+ /**
+ * Return the start padding of the parent RecyclerView
+ *
+ * @return Padding in pixels
+ */
+ public int getPaddingStart() {
+ return mRecyclerView != null ? mRecyclerView.getPaddingStart() : 0;
+ }
+
+ /**
+ * Return the end padding of the parent RecyclerView
+ *
+ * @return Padding in pixels
+ */
+ public int getPaddingEnd() {
+ return mRecyclerView != null ? mRecyclerView.getPaddingEnd() : 0;
+ }
+
+ /**
+ * Returns true if the RecyclerView this LayoutManager is bound to has focus.
+ *
+ * @return True if the RecyclerView has focus, false otherwise.
+ * @see View#isFocused()
+ */
+ public boolean isFocused() {
+ return mRecyclerView != null && mRecyclerView.isFocused();
+ }
+
+ /**
+ * Returns true if the RecyclerView this LayoutManager is bound to has or contains focus.
+ *
+ * @return true if the RecyclerView has or contains focus
+ * @see View#hasFocus()
+ */
+ public boolean hasFocus() {
+ return mRecyclerView != null && mRecyclerView.hasFocus();
+ }
+
+ /**
+ * Returns the item View which has or contains focus.
+ *
+ * @return A direct child of RecyclerView which has focus or contains the focused child.
+ */
+ public View getFocusedChild() {
+ if (mRecyclerView == null) {
+ return null;
+ }
+ final View focused = mRecyclerView.getFocusedChild();
+ if (focused == null || mChildHelper.isHidden(focused)) {
+ return null;
+ }
+ return focused;
+ }
+
+ /**
+ * Returns the number of items in the adapter bound to the parent RecyclerView.
+ * <p>
+ * Note that this number is not necessarily equal to
+ * {@link State#getItemCount() State#getItemCount()}. In methods where {@link State} is
+ * available, you should use {@link State#getItemCount() State#getItemCount()} instead.
+ * For more details, check the documentation for
+ * {@link State#getItemCount() State#getItemCount()}.
+ *
+ * @return The number of items in the bound adapter
+ * @see State#getItemCount()
+ */
+ public int getItemCount() {
+ final Adapter a = mRecyclerView != null ? mRecyclerView.getAdapter() : null;
+ return a != null ? a.getItemCount() : 0;
+ }
+
+ /**
+ * Offset all child views attached to the parent RecyclerView by dx pixels along
+ * the horizontal axis.
+ *
+ * @param dx Pixels to offset by
+ */
+ public void offsetChildrenHorizontal(int dx) {
+ if (mRecyclerView != null) {
+ mRecyclerView.offsetChildrenHorizontal(dx);
+ }
+ }
+
+ /**
+ * Offset all child views attached to the parent RecyclerView by dy pixels along
+ * the vertical axis.
+ *
+ * @param dy Pixels to offset by
+ */
+ public void offsetChildrenVertical(int dy) {
+ if (mRecyclerView != null) {
+ mRecyclerView.offsetChildrenVertical(dy);
+ }
+ }
+
+ /**
+ * Flags a view so that it will not be scrapped or recycled.
+ * <p>
+ * Scope of ignoring a child is strictly restricted to position tracking, scrapping and
+ * recyling. Methods like {@link #removeAndRecycleAllViews(Recycler)} will ignore the child
+ * whereas {@link #removeAllViews()} or {@link #offsetChildrenHorizontal(int)} will not
+ * ignore the child.
+ * <p>
+ * Before this child can be recycled again, you have to call
+ * {@link #stopIgnoringView(View)}.
+ * <p>
+ * You can call this method only if your LayoutManger is in onLayout or onScroll callback.
+ *
+ * @param view View to ignore.
+ * @see #stopIgnoringView(View)
+ */
+ public void ignoreView(View view) {
+ if (view.getParent() != mRecyclerView || mRecyclerView.indexOfChild(view) == -1) {
+ // checking this because calling this method on a recycled or detached view may
+ // cause loss of state.
+ throw new IllegalArgumentException("View should be fully attached to be ignored");
+ }
+ final ViewHolder vh = getChildViewHolderInt(view);
+ vh.addFlags(ViewHolder.FLAG_IGNORE);
+ mRecyclerView.mViewInfoStore.removeViewHolder(vh);
+ }
+
+ /**
+ * View can be scrapped and recycled again.
+ * <p>
+ * Note that calling this method removes all information in the view holder.
+ * <p>
+ * You can call this method only if your LayoutManger is in onLayout or onScroll callback.
+ *
+ * @param view View to ignore.
+ */
+ public void stopIgnoringView(View view) {
+ final ViewHolder vh = getChildViewHolderInt(view);
+ vh.stopIgnoring();
+ vh.resetInternal();
+ vh.addFlags(ViewHolder.FLAG_INVALID);
+ }
+
+ /**
+ * Temporarily detach and scrap all currently attached child views. Views will be scrapped
+ * into the given Recycler. The Recycler may prefer to reuse scrap views before
+ * other views that were previously recycled.
+ *
+ * @param recycler Recycler to scrap views into
+ */
+ public void detachAndScrapAttachedViews(Recycler recycler) {
+ final int childCount = getChildCount();
+ for (int i = childCount - 1; i >= 0; i--) {
+ final View v = getChildAt(i);
+ scrapOrRecycleView(recycler, i, v);
+ }
+ }
+
+ private void scrapOrRecycleView(Recycler recycler, int index, View view) {
+ final ViewHolder viewHolder = getChildViewHolderInt(view);
+ if (viewHolder.shouldIgnore()) {
+ if (DEBUG) {
+ Log.d(TAG, "ignoring view " + viewHolder);
+ }
+ return;
+ }
+ if (viewHolder.isInvalid() && !viewHolder.isRemoved()
+ && !mRecyclerView.mAdapter.hasStableIds()) {
+ removeViewAt(index);
+ recycler.recycleViewHolderInternal(viewHolder);
+ } else {
+ detachViewAt(index);
+ recycler.scrapView(view);
+ mRecyclerView.mViewInfoStore.onViewDetached(viewHolder);
+ }
+ }
+
+ /**
+ * Recycles the scrapped views.
+ * <p>
+ * When a view is detached and removed, it does not trigger a ViewGroup invalidate. This is
+ * the expected behavior if scrapped views are used for animations. Otherwise, we need to
+ * call remove and invalidate RecyclerView to ensure UI update.
+ *
+ * @param recycler Recycler
+ */
+ void removeAndRecycleScrapInt(Recycler recycler) {
+ final int scrapCount = recycler.getScrapCount();
+ // Loop backward, recycler might be changed by removeDetachedView()
+ for (int i = scrapCount - 1; i >= 0; i--) {
+ final View scrap = recycler.getScrapViewAt(i);
+ final ViewHolder vh = getChildViewHolderInt(scrap);
+ if (vh.shouldIgnore()) {
+ continue;
+ }
+ // If the scrap view is animating, we need to cancel them first. If we cancel it
+ // here, ItemAnimator callback may recycle it which will cause double recycling.
+ // To avoid this, we mark it as not recycleable before calling the item animator.
+ // Since removeDetachedView calls a user API, a common mistake (ending animations on
+ // the view) may recycle it too, so we guard it before we call user APIs.
+ vh.setIsRecyclable(false);
+ if (vh.isTmpDetached()) {
+ mRecyclerView.removeDetachedView(scrap, false);
+ }
+ if (mRecyclerView.mItemAnimator != null) {
+ mRecyclerView.mItemAnimator.endAnimation(vh);
+ }
+ vh.setIsRecyclable(true);
+ recycler.quickRecycleScrapView(scrap);
+ }
+ recycler.clearScrap();
+ if (scrapCount > 0) {
+ mRecyclerView.invalidate();
+ }
+ }
+
+
+ /**
+ * Measure a child view using standard measurement policy, taking the padding
+ * of the parent RecyclerView and any added item decorations into account.
+ *
+ * <p>If the RecyclerView can be scrolled in either dimension the caller may
+ * pass 0 as the widthUsed or heightUsed parameters as they will be irrelevant.</p>
+ *
+ * @param child Child view to measure
+ * @param widthUsed Width in pixels currently consumed by other views, if relevant
+ * @param heightUsed Height in pixels currently consumed by other views, if relevant
+ */
+ public void measureChild(View child, int widthUsed, int heightUsed) {
+ final LayoutParams lp = (LayoutParams) child.getLayoutParams();
+
+ final Rect insets = mRecyclerView.getItemDecorInsetsForChild(child);
+ widthUsed += insets.left + insets.right;
+ heightUsed += insets.top + insets.bottom;
+ final int widthSpec = getChildMeasureSpec(getWidth(), getWidthMode(),
+ getPaddingLeft() + getPaddingRight() + widthUsed, lp.width,
+ canScrollHorizontally());
+ final int heightSpec = getChildMeasureSpec(getHeight(), getHeightMode(),
+ getPaddingTop() + getPaddingBottom() + heightUsed, lp.height,
+ canScrollVertically());
+ if (shouldMeasureChild(child, widthSpec, heightSpec, lp)) {
+ child.measure(widthSpec, heightSpec);
+ }
+ }
+
+ /**
+ * RecyclerView internally does its own View measurement caching which should help with
+ * WRAP_CONTENT.
+ * <p>
+ * Use this method if the View is already measured once in this layout pass.
+ */
+ boolean shouldReMeasureChild(View child, int widthSpec, int heightSpec, LayoutParams lp) {
+ return !mMeasurementCacheEnabled
+ || !isMeasurementUpToDate(child.getMeasuredWidth(), widthSpec, lp.width)
+ || !isMeasurementUpToDate(child.getMeasuredHeight(), heightSpec, lp.height);
+ }
+
+ // we may consider making this public
+ /**
+ * RecyclerView internally does its own View measurement caching which should help with
+ * WRAP_CONTENT.
+ * <p>
+ * Use this method if the View is not yet measured and you need to decide whether to
+ * measure this View or not.
+ */
+ boolean shouldMeasureChild(View child, int widthSpec, int heightSpec, LayoutParams lp) {
+ return child.isLayoutRequested()
+ || !mMeasurementCacheEnabled
+ || !isMeasurementUpToDate(child.getWidth(), widthSpec, lp.width)
+ || !isMeasurementUpToDate(child.getHeight(), heightSpec, lp.height);
+ }
+
+ /**
+ * In addition to the View Framework's measurement cache, RecyclerView uses its own
+ * additional measurement cache for its children to avoid re-measuring them when not
+ * necessary. It is on by default but it can be turned off via
+ * {@link #setMeasurementCacheEnabled(boolean)}.
+ *
+ * @return True if measurement cache is enabled, false otherwise.
+ *
+ * @see #setMeasurementCacheEnabled(boolean)
+ */
+ public boolean isMeasurementCacheEnabled() {
+ return mMeasurementCacheEnabled;
+ }
+
+ /**
+ * Sets whether RecyclerView should use its own measurement cache for the children. This is
+ * a more aggressive cache than the framework uses.
+ *
+ * @param measurementCacheEnabled True to enable the measurement cache, false otherwise.
+ *
+ * @see #isMeasurementCacheEnabled()
+ */
+ public void setMeasurementCacheEnabled(boolean measurementCacheEnabled) {
+ mMeasurementCacheEnabled = measurementCacheEnabled;
+ }
+
+ private static boolean isMeasurementUpToDate(int childSize, int spec, int dimension) {
+ final int specMode = MeasureSpec.getMode(spec);
+ final int specSize = MeasureSpec.getSize(spec);
+ if (dimension > 0 && childSize != dimension) {
+ return false;
+ }
+ switch (specMode) {
+ case MeasureSpec.UNSPECIFIED:
+ return true;
+ case MeasureSpec.AT_MOST:
+ return specSize >= childSize;
+ case MeasureSpec.EXACTLY:
+ return specSize == childSize;
+ }
+ return false;
+ }
+
+ /**
+ * Measure a child view using standard measurement policy, taking the padding
+ * of the parent RecyclerView, any added item decorations and the child margins
+ * into account.
+ *
+ * <p>If the RecyclerView can be scrolled in either dimension the caller may
+ * pass 0 as the widthUsed or heightUsed parameters as they will be irrelevant.</p>
+ *
+ * @param child Child view to measure
+ * @param widthUsed Width in pixels currently consumed by other views, if relevant
+ * @param heightUsed Height in pixels currently consumed by other views, if relevant
+ */
+ public void measureChildWithMargins(View child, int widthUsed, int heightUsed) {
+ final LayoutParams lp = (LayoutParams) child.getLayoutParams();
+
+ final Rect insets = mRecyclerView.getItemDecorInsetsForChild(child);
+ widthUsed += insets.left + insets.right;
+ heightUsed += insets.top + insets.bottom;
+
+ final int widthSpec = getChildMeasureSpec(getWidth(), getWidthMode(),
+ getPaddingLeft() + getPaddingRight()
+ + lp.leftMargin + lp.rightMargin + widthUsed, lp.width,
+ canScrollHorizontally());
+ final int heightSpec = getChildMeasureSpec(getHeight(), getHeightMode(),
+ getPaddingTop() + getPaddingBottom()
+ + lp.topMargin + lp.bottomMargin + heightUsed, lp.height,
+ canScrollVertically());
+ if (shouldMeasureChild(child, widthSpec, heightSpec, lp)) {
+ child.measure(widthSpec, heightSpec);
+ }
+ }
+
+ /**
+ * Calculate a MeasureSpec value for measuring a child view in one dimension.
+ *
+ * @param parentSize Size of the parent view where the child will be placed
+ * @param padding Total space currently consumed by other elements of the parent
+ * @param childDimension Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT.
+ * Generally obtained from the child view's LayoutParams
+ * @param canScroll true if the parent RecyclerView can scroll in this dimension
+ *
+ * @return a MeasureSpec value for the child view
+ * @deprecated use {@link #getChildMeasureSpec(int, int, int, int, boolean)}
+ */
+ @Deprecated
+ public static int getChildMeasureSpec(int parentSize, int padding, int childDimension,
+ boolean canScroll) {
+ int size = Math.max(0, parentSize - padding);
+ int resultSize = 0;
+ int resultMode = 0;
+ if (canScroll) {
+ if (childDimension >= 0) {
+ resultSize = childDimension;
+ resultMode = MeasureSpec.EXACTLY;
+ } else {
+ // MATCH_PARENT can't be applied since we can scroll in this dimension, wrap
+ // instead using UNSPECIFIED.
+ resultSize = 0;
+ resultMode = MeasureSpec.UNSPECIFIED;
+ }
+ } else {
+ if (childDimension >= 0) {
+ resultSize = childDimension;
+ resultMode = MeasureSpec.EXACTLY;
+ } else if (childDimension == LayoutParams.MATCH_PARENT) {
+ resultSize = size;
+ // TODO this should be my spec.
+ resultMode = MeasureSpec.EXACTLY;
+ } else if (childDimension == LayoutParams.WRAP_CONTENT) {
+ resultSize = size;
+ resultMode = MeasureSpec.AT_MOST;
+ }
+ }
+ return MeasureSpec.makeMeasureSpec(resultSize, resultMode);
+ }
+
+ /**
+ * Calculate a MeasureSpec value for measuring a child view in one dimension.
+ *
+ * @param parentSize Size of the parent view where the child will be placed
+ * @param parentMode The measurement spec mode of the parent
+ * @param padding Total space currently consumed by other elements of parent
+ * @param childDimension Desired size of the child view, or MATCH_PARENT/WRAP_CONTENT.
+ * Generally obtained from the child view's LayoutParams
+ * @param canScroll true if the parent RecyclerView can scroll in this dimension
+ *
+ * @return a MeasureSpec value for the child view
+ */
+ public static int getChildMeasureSpec(int parentSize, int parentMode, int padding,
+ int childDimension, boolean canScroll) {
+ int size = Math.max(0, parentSize - padding);
+ int resultSize = 0;
+ int resultMode = 0;
+ if (canScroll) {
+ if (childDimension >= 0) {
+ resultSize = childDimension;
+ resultMode = MeasureSpec.EXACTLY;
+ } else if (childDimension == LayoutParams.MATCH_PARENT) {
+ switch (parentMode) {
+ case MeasureSpec.AT_MOST:
+ case MeasureSpec.EXACTLY:
+ resultSize = size;
+ resultMode = parentMode;
+ break;
+ case MeasureSpec.UNSPECIFIED:
+ resultSize = 0;
+ resultMode = MeasureSpec.UNSPECIFIED;
+ break;
+ }
+ } else if (childDimension == LayoutParams.WRAP_CONTENT) {
+ resultSize = 0;
+ resultMode = MeasureSpec.UNSPECIFIED;
+ }
+ } else {
+ if (childDimension >= 0) {
+ resultSize = childDimension;
+ resultMode = MeasureSpec.EXACTLY;
+ } else if (childDimension == LayoutParams.MATCH_PARENT) {
+ resultSize = size;
+ resultMode = parentMode;
+ } else if (childDimension == LayoutParams.WRAP_CONTENT) {
+ resultSize = size;
+ if (parentMode == MeasureSpec.AT_MOST || parentMode == MeasureSpec.EXACTLY) {
+ resultMode = MeasureSpec.AT_MOST;
+ } else {
+ resultMode = MeasureSpec.UNSPECIFIED;
+ }
+
+ }
+ }
+ //noinspection WrongConstant
+ return MeasureSpec.makeMeasureSpec(resultSize, resultMode);
+ }
+
+ /**
+ * Returns the measured width of the given child, plus the additional size of
+ * any insets applied by {@link ItemDecoration ItemDecorations}.
+ *
+ * @param child Child view to query
+ * @return child's measured width plus <code>ItemDecoration</code> insets
+ *
+ * @see View#getMeasuredWidth()
+ */
+ public int getDecoratedMeasuredWidth(View child) {
+ final Rect insets = ((LayoutParams) child.getLayoutParams()).mDecorInsets;
+ return child.getMeasuredWidth() + insets.left + insets.right;
+ }
+
+ /**
+ * Returns the measured height of the given child, plus the additional size of
+ * any insets applied by {@link ItemDecoration ItemDecorations}.
+ *
+ * @param child Child view to query
+ * @return child's measured height plus <code>ItemDecoration</code> insets
+ *
+ * @see View#getMeasuredHeight()
+ */
+ public int getDecoratedMeasuredHeight(View child) {
+ final Rect insets = ((LayoutParams) child.getLayoutParams()).mDecorInsets;
+ return child.getMeasuredHeight() + insets.top + insets.bottom;
+ }
+
+ /**
+ * Lay out the given child view within the RecyclerView using coordinates that
+ * include any current {@link ItemDecoration ItemDecorations}.
+ *
+ * <p>LayoutManagers should prefer working in sizes and coordinates that include
+ * item decoration insets whenever possible. This allows the LayoutManager to effectively
+ * ignore decoration insets within measurement and layout code. See the following
+ * methods:</p>
+ * <ul>
+ * <li>{@link #layoutDecoratedWithMargins(View, int, int, int, int)}</li>
+ * <li>{@link #getDecoratedBoundsWithMargins(View, Rect)}</li>
+ * <li>{@link #measureChild(View, int, int)}</li>
+ * <li>{@link #measureChildWithMargins(View, int, int)}</li>
+ * <li>{@link #getDecoratedLeft(View)}</li>
+ * <li>{@link #getDecoratedTop(View)}</li>
+ * <li>{@link #getDecoratedRight(View)}</li>
+ * <li>{@link #getDecoratedBottom(View)}</li>
+ * <li>{@link #getDecoratedMeasuredWidth(View)}</li>
+ * <li>{@link #getDecoratedMeasuredHeight(View)}</li>
+ * </ul>
+ *
+ * @param child Child to lay out
+ * @param left Left edge, with item decoration insets included
+ * @param top Top edge, with item decoration insets included
+ * @param right Right edge, with item decoration insets included
+ * @param bottom Bottom edge, with item decoration insets included
+ *
+ * @see View#layout(int, int, int, int)
+ * @see #layoutDecoratedWithMargins(View, int, int, int, int)
+ */
+ public void layoutDecorated(View child, int left, int top, int right, int bottom) {
+ final Rect insets = ((LayoutParams) child.getLayoutParams()).mDecorInsets;
+ child.layout(left + insets.left, top + insets.top, right - insets.right,
+ bottom - insets.bottom);
+ }
+
+ /**
+ * Lay out the given child view within the RecyclerView using coordinates that
+ * include any current {@link ItemDecoration ItemDecorations} and margins.
+ *
+ * <p>LayoutManagers should prefer working in sizes and coordinates that include
+ * item decoration insets whenever possible. This allows the LayoutManager to effectively
+ * ignore decoration insets within measurement and layout code. See the following
+ * methods:</p>
+ * <ul>
+ * <li>{@link #layoutDecorated(View, int, int, int, int)}</li>
+ * <li>{@link #measureChild(View, int, int)}</li>
+ * <li>{@link #measureChildWithMargins(View, int, int)}</li>
+ * <li>{@link #getDecoratedLeft(View)}</li>
+ * <li>{@link #getDecoratedTop(View)}</li>
+ * <li>{@link #getDecoratedRight(View)}</li>
+ * <li>{@link #getDecoratedBottom(View)}</li>
+ * <li>{@link #getDecoratedMeasuredWidth(View)}</li>
+ * <li>{@link #getDecoratedMeasuredHeight(View)}</li>
+ * </ul>
+ *
+ * @param child Child to lay out
+ * @param left Left edge, with item decoration insets and left margin included
+ * @param top Top edge, with item decoration insets and top margin included
+ * @param right Right edge, with item decoration insets and right margin included
+ * @param bottom Bottom edge, with item decoration insets and bottom margin included
+ *
+ * @see View#layout(int, int, int, int)
+ * @see #layoutDecorated(View, int, int, int, int)
+ */
+ public void layoutDecoratedWithMargins(View child, int left, int top, int right,
+ int bottom) {
+ final LayoutParams lp = (LayoutParams) child.getLayoutParams();
+ final Rect insets = lp.mDecorInsets;
+ child.layout(left + insets.left + lp.leftMargin, top + insets.top + lp.topMargin,
+ right - insets.right - lp.rightMargin,
+ bottom - insets.bottom - lp.bottomMargin);
+ }
+
+ /**
+ * Calculates the bounding box of the View while taking into account its matrix changes
+ * (translation, scale etc) with respect to the RecyclerView.
+ * <p>
+ * If {@code includeDecorInsets} is {@code true}, they are applied first before applying
+ * the View's matrix so that the decor offsets also go through the same transformation.
+ *
+ * @param child The ItemView whose bounding box should be calculated.
+ * @param includeDecorInsets True if the decor insets should be included in the bounding box
+ * @param out The rectangle into which the output will be written.
+ */
+ public void getTransformedBoundingBox(View child, boolean includeDecorInsets, Rect out) {
+ if (includeDecorInsets) {
+ Rect insets = ((LayoutParams) child.getLayoutParams()).mDecorInsets;
+ out.set(-insets.left, -insets.top,
+ child.getWidth() + insets.right, child.getHeight() + insets.bottom);
+ } else {
+ out.set(0, 0, child.getWidth(), child.getHeight());
+ }
+
+ if (mRecyclerView != null) {
+ final Matrix childMatrix = child.getMatrix();
+ if (childMatrix != null && !childMatrix.isIdentity()) {
+ final RectF tempRectF = mRecyclerView.mTempRectF;
+ tempRectF.set(out);
+ childMatrix.mapRect(tempRectF);
+ out.set(
+ (int) Math.floor(tempRectF.left),
+ (int) Math.floor(tempRectF.top),
+ (int) Math.ceil(tempRectF.right),
+ (int) Math.ceil(tempRectF.bottom)
+ );
+ }
+ }
+ out.offset(child.getLeft(), child.getTop());
+ }
+
+ /**
+ * Returns the bounds of the view including its decoration and margins.
+ *
+ * @param view The view element to check
+ * @param outBounds A rect that will receive the bounds of the element including its
+ * decoration and margins.
+ */
+ public void getDecoratedBoundsWithMargins(View view, Rect outBounds) {
+ RecyclerView.getDecoratedBoundsWithMarginsInt(view, outBounds);
+ }
+
+ /**
+ * Returns the left edge of the given child view within its parent, offset by any applied
+ * {@link ItemDecoration ItemDecorations}.
+ *
+ * @param child Child to query
+ * @return Child left edge with offsets applied
+ * @see #getLeftDecorationWidth(View)
+ */
+ public int getDecoratedLeft(View child) {
+ return child.getLeft() - getLeftDecorationWidth(child);
+ }
+
+ /**
+ * Returns the top edge of the given child view within its parent, offset by any applied
+ * {@link ItemDecoration ItemDecorations}.
+ *
+ * @param child Child to query
+ * @return Child top edge with offsets applied
+ * @see #getTopDecorationHeight(View)
+ */
+ public int getDecoratedTop(View child) {
+ return child.getTop() - getTopDecorationHeight(child);
+ }
+
+ /**
+ * Returns the right edge of the given child view within its parent, offset by any applied
+ * {@link ItemDecoration ItemDecorations}.
+ *
+ * @param child Child to query
+ * @return Child right edge with offsets applied
+ * @see #getRightDecorationWidth(View)
+ */
+ public int getDecoratedRight(View child) {
+ return child.getRight() + getRightDecorationWidth(child);
+ }
+
+ /**
+ * Returns the bottom edge of the given child view within its parent, offset by any applied
+ * {@link ItemDecoration ItemDecorations}.
+ *
+ * @param child Child to query
+ * @return Child bottom edge with offsets applied
+ * @see #getBottomDecorationHeight(View)
+ */
+ public int getDecoratedBottom(View child) {
+ return child.getBottom() + getBottomDecorationHeight(child);
+ }
+
+ /**
+ * Calculates the item decor insets applied to the given child and updates the provided
+ * Rect instance with the inset values.
+ * <ul>
+ * <li>The Rect's left is set to the total width of left decorations.</li>
+ * <li>The Rect's top is set to the total height of top decorations.</li>
+ * <li>The Rect's right is set to the total width of right decorations.</li>
+ * <li>The Rect's bottom is set to total height of bottom decorations.</li>
+ * </ul>
+ * <p>
+ * Note that item decorations are automatically calculated when one of the LayoutManager's
+ * measure child methods is called. If you need to measure the child with custom specs via
+ * {@link View#measure(int, int)}, you can use this method to get decorations.
+ *
+ * @param child The child view whose decorations should be calculated
+ * @param outRect The Rect to hold result values
+ */
+ public void calculateItemDecorationsForChild(View child, Rect outRect) {
+ if (mRecyclerView == null) {
+ outRect.set(0, 0, 0, 0);
+ return;
+ }
+ Rect insets = mRecyclerView.getItemDecorInsetsForChild(child);
+ outRect.set(insets);
+ }
+
+ /**
+ * Returns the total height of item decorations applied to child's top.
+ * <p>
+ * Note that this value is not updated until the View is measured or
+ * {@link #calculateItemDecorationsForChild(View, Rect)} is called.
+ *
+ * @param child Child to query
+ * @return The total height of item decorations applied to the child's top.
+ * @see #getDecoratedTop(View)
+ * @see #calculateItemDecorationsForChild(View, Rect)
+ */
+ public int getTopDecorationHeight(View child) {
+ return ((LayoutParams) child.getLayoutParams()).mDecorInsets.top;
+ }
+
+ /**
+ * Returns the total height of item decorations applied to child's bottom.
+ * <p>
+ * Note that this value is not updated until the View is measured or
+ * {@link #calculateItemDecorationsForChild(View, Rect)} is called.
+ *
+ * @param child Child to query
+ * @return The total height of item decorations applied to the child's bottom.
+ * @see #getDecoratedBottom(View)
+ * @see #calculateItemDecorationsForChild(View, Rect)
+ */
+ public int getBottomDecorationHeight(View child) {
+ return ((LayoutParams) child.getLayoutParams()).mDecorInsets.bottom;
+ }
+
+ /**
+ * Returns the total width of item decorations applied to child's left.
+ * <p>
+ * Note that this value is not updated until the View is measured or
+ * {@link #calculateItemDecorationsForChild(View, Rect)} is called.
+ *
+ * @param child Child to query
+ * @return The total width of item decorations applied to the child's left.
+ * @see #getDecoratedLeft(View)
+ * @see #calculateItemDecorationsForChild(View, Rect)
+ */
+ public int getLeftDecorationWidth(View child) {
+ return ((LayoutParams) child.getLayoutParams()).mDecorInsets.left;
+ }
+
+ /**
+ * Returns the total width of item decorations applied to child's right.
+ * <p>
+ * Note that this value is not updated until the View is measured or
+ * {@link #calculateItemDecorationsForChild(View, Rect)} is called.
+ *
+ * @param child Child to query
+ * @return The total width of item decorations applied to the child's right.
+ * @see #getDecoratedRight(View)
+ * @see #calculateItemDecorationsForChild(View, Rect)
+ */
+ public int getRightDecorationWidth(View child) {
+ return ((LayoutParams) child.getLayoutParams()).mDecorInsets.right;
+ }
+
+ /**
+ * Called when searching for a focusable view in the given direction has failed
+ * for the current content of the RecyclerView.
+ *
+ * <p>This is the LayoutManager's opportunity to populate views in the given direction
+ * to fulfill the request if it can. The LayoutManager should attach and return
+ * the view to be focused. The default implementation returns null.</p>
+ *
+ * @param focused The currently focused view
+ * @param direction One of {@link View#FOCUS_UP}, {@link View#FOCUS_DOWN},
+ * {@link View#FOCUS_LEFT}, {@link View#FOCUS_RIGHT},
+ * {@link View#FOCUS_BACKWARD}, {@link View#FOCUS_FORWARD}
+ * or 0 for not applicable
+ * @param recycler The recycler to use for obtaining views for currently offscreen items
+ * @param state Transient state of RecyclerView
+ * @return The chosen view to be focused
+ */
+ @Nullable
+ public View onFocusSearchFailed(View focused, int direction, Recycler recycler,
+ State state) {
+ return null;
+ }
+
+ /**
+ * This method gives a LayoutManager an opportunity to intercept the initial focus search
+ * before the default behavior of {@link FocusFinder} is used. If this method returns
+ * null FocusFinder will attempt to find a focusable child view. If it fails
+ * then {@link #onFocusSearchFailed(View, int, RecyclerView.Recycler, RecyclerView.State)}
+ * will be called to give the LayoutManager an opportunity to add new views for items
+ * that did not have attached views representing them. The LayoutManager should not add
+ * or remove views from this method.
+ *
+ * @param focused The currently focused view
+ * @param direction One of {@link View#FOCUS_UP}, {@link View#FOCUS_DOWN},
+ * {@link View#FOCUS_LEFT}, {@link View#FOCUS_RIGHT},
+ * {@link View#FOCUS_BACKWARD}, {@link View#FOCUS_FORWARD}
+ * @return A descendant view to focus or null to fall back to default behavior.
+ * The default implementation returns null.
+ */
+ public View onInterceptFocusSearch(View focused, int direction) {
+ return null;
+ }
+
+ /**
+ * Called when a child of the RecyclerView wants a particular rectangle to be positioned
+ * onto the screen. See {@link ViewParent#requestChildRectangleOnScreen(android.view.View,
+ * android.graphics.Rect, boolean)} for more details.
+ *
+ * <p>The base implementation will attempt to perform a standard programmatic scroll
+ * to bring the given rect into view, within the padded area of the RecyclerView.</p>
+ *
+ * @param child The direct child making the request.
+ * @param rect The rectangle in the child's coordinates the child
+ * wishes to be on the screen.
+ * @param immediate True to forbid animated or delayed scrolling,
+ * false otherwise
+ * @return Whether the group scrolled to handle the operation
+ */
+ public boolean requestChildRectangleOnScreen(RecyclerView parent, View child, Rect rect,
+ boolean immediate) {
+ final int parentLeft = getPaddingLeft();
+ final int parentTop = getPaddingTop();
+ final int parentRight = getWidth() - getPaddingRight();
+ final int parentBottom = getHeight() - getPaddingBottom();
+ final int childLeft = child.getLeft() + rect.left - child.getScrollX();
+ final int childTop = child.getTop() + rect.top - child.getScrollY();
+ final int childRight = childLeft + rect.width();
+ final int childBottom = childTop + rect.height();
+
+ final int offScreenLeft = Math.min(0, childLeft - parentLeft);
+ final int offScreenTop = Math.min(0, childTop - parentTop);
+ final int offScreenRight = Math.max(0, childRight - parentRight);
+ final int offScreenBottom = Math.max(0, childBottom - parentBottom);
+
+ // Favor the "start" layout direction over the end when bringing one side or the other
+ // of a large rect into view. If we decide to bring in end because start is already
+ // visible, limit the scroll such that start won't go out of bounds.
+ final int dx;
+ if (getLayoutDirection() == View.LAYOUT_DIRECTION_RTL) {
+ dx = offScreenRight != 0 ? offScreenRight
+ : Math.max(offScreenLeft, childRight - parentRight);
+ } else {
+ dx = offScreenLeft != 0 ? offScreenLeft
+ : Math.min(childLeft - parentLeft, offScreenRight);
+ }
+
+ // Favor bringing the top into view over the bottom. If top is already visible and
+ // we should scroll to make bottom visible, make sure top does not go out of bounds.
+ final int dy = offScreenTop != 0 ? offScreenTop
+ : Math.min(childTop - parentTop, offScreenBottom);
+
+ if (dx != 0 || dy != 0) {
+ if (immediate) {
+ parent.scrollBy(dx, dy);
+ } else {
+ parent.smoothScrollBy(dx, dy);
+ }
+ return true;
+ }
+ return false;
+ }
+
+ /**
+ * @deprecated Use {@link #onRequestChildFocus(RecyclerView, State, View, View)}
+ */
+ @Deprecated
+ public boolean onRequestChildFocus(RecyclerView parent, View child, View focused) {
+ // eat the request if we are in the middle of a scroll or layout
+ return isSmoothScrolling() || parent.isComputingLayout();
+ }
+
+ /**
+ * Called when a descendant view of the RecyclerView requests focus.
+ *
+ * <p>A LayoutManager wishing to keep focused views aligned in a specific
+ * portion of the view may implement that behavior in an override of this method.</p>
+ *
+ * <p>If the LayoutManager executes different behavior that should override the default
+ * behavior of scrolling the focused child on screen instead of running alongside it,
+ * this method should return true.</p>
+ *
+ * @param parent The RecyclerView hosting this LayoutManager
+ * @param state Current state of RecyclerView
+ * @param child Direct child of the RecyclerView containing the newly focused view
+ * @param focused The newly focused view. This may be the same view as child or it may be
+ * null
+ * @return true if the default scroll behavior should be suppressed
+ */
+ public boolean onRequestChildFocus(RecyclerView parent, State state, View child,
+ View focused) {
+ return onRequestChildFocus(parent, child, focused);
+ }
+
+ /**
+ * Called if the RecyclerView this LayoutManager is bound to has a different adapter set.
+ * The LayoutManager may use this opportunity to clear caches and configure state such
+ * that it can relayout appropriately with the new data and potentially new view types.
+ *
+ * <p>The default implementation removes all currently attached views.</p>
+ *
+ * @param oldAdapter The previous adapter instance. Will be null if there was previously no
+ * adapter.
+ * @param newAdapter The new adapter instance. Might be null if
+ * {@link #setAdapter(RecyclerView.Adapter)} is called with {@code null}.
+ */
+ public void onAdapterChanged(Adapter oldAdapter, Adapter newAdapter) {
+ }
+
+ /**
+ * Called to populate focusable views within the RecyclerView.
+ *
+ * <p>The LayoutManager implementation should return <code>true</code> if the default
+ * behavior of {@link ViewGroup#addFocusables(java.util.ArrayList, int)} should be
+ * suppressed.</p>
+ *
+ * <p>The default implementation returns <code>false</code> to trigger RecyclerView
+ * to fall back to the default ViewGroup behavior.</p>
+ *
+ * @param recyclerView The RecyclerView hosting this LayoutManager
+ * @param views List of output views. This method should add valid focusable views
+ * to this list.
+ * @param direction One of {@link View#FOCUS_UP}, {@link View#FOCUS_DOWN},
+ * {@link View#FOCUS_LEFT}, {@link View#FOCUS_RIGHT},
+ * {@link View#FOCUS_BACKWARD}, {@link View#FOCUS_FORWARD}
+ * @param focusableMode The type of focusables to be added.
+ *
+ * @return true to suppress the default behavior, false to add default focusables after
+ * this method returns.
+ *
+ * @see #FOCUSABLES_ALL
+ * @see #FOCUSABLES_TOUCH_MODE
+ */
+ public boolean onAddFocusables(RecyclerView recyclerView, ArrayList<View> views,
+ int direction, int focusableMode) {
+ return false;
+ }
+
+ /**
+ * Called when {@link Adapter#notifyDataSetChanged()} is triggered instead of giving
+ * detailed information on what has actually changed.
+ *
+ * @param recyclerView
+ */
+ public void onItemsChanged(RecyclerView recyclerView) {
+ }
+
+ /**
+ * Called when items have been added to the adapter. The LayoutManager may choose to
+ * requestLayout if the inserted items would require refreshing the currently visible set
+ * of child views. (e.g. currently empty space would be filled by appended items, etc.)
+ *
+ * @param recyclerView
+ * @param positionStart
+ * @param itemCount
+ */
+ public void onItemsAdded(RecyclerView recyclerView, int positionStart, int itemCount) {
+ }
+
+ /**
+ * Called when items have been removed from the adapter.
+ *
+ * @param recyclerView
+ * @param positionStart
+ * @param itemCount
+ */
+ public void onItemsRemoved(RecyclerView recyclerView, int positionStart, int itemCount) {
+ }
+
+ /**
+ * Called when items have been changed in the adapter.
+ * To receive payload, override {@link #onItemsUpdated(RecyclerView, int, int, Object)}
+ * instead, then this callback will not be invoked.
+ *
+ * @param recyclerView
+ * @param positionStart
+ * @param itemCount
+ */
+ public void onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount) {
+ }
+
+ /**
+ * Called when items have been changed in the adapter and with optional payload.
+ * Default implementation calls {@link #onItemsUpdated(RecyclerView, int, int)}.
+ *
+ * @param recyclerView
+ * @param positionStart
+ * @param itemCount
+ * @param payload
+ */
+ public void onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount,
+ Object payload) {
+ onItemsUpdated(recyclerView, positionStart, itemCount);
+ }
+
+ /**
+ * Called when an item is moved withing the adapter.
+ * <p>
+ * Note that, an item may also change position in response to another ADD/REMOVE/MOVE
+ * operation. This callback is only called if and only if {@link Adapter#notifyItemMoved}
+ * is called.
+ *
+ * @param recyclerView
+ * @param from
+ * @param to
+ * @param itemCount
+ */
+ public void onItemsMoved(RecyclerView recyclerView, int from, int to, int itemCount) {
+
+ }
+
+
+ /**
+ * <p>Override this method if you want to support scroll bars.</p>
+ *
+ * <p>Read {@link RecyclerView#computeHorizontalScrollExtent()} for details.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * @param state Current state of RecyclerView
+ * @return The horizontal extent of the scrollbar's thumb
+ * @see RecyclerView#computeHorizontalScrollExtent()
+ */
+ public int computeHorizontalScrollExtent(State state) {
+ return 0;
+ }
+
+ /**
+ * <p>Override this method if you want to support scroll bars.</p>
+ *
+ * <p>Read {@link RecyclerView#computeHorizontalScrollOffset()} for details.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * @param state Current State of RecyclerView where you can find total item count
+ * @return The horizontal offset of the scrollbar's thumb
+ * @see RecyclerView#computeHorizontalScrollOffset()
+ */
+ public int computeHorizontalScrollOffset(State state) {
+ return 0;
+ }
+
+ /**
+ * <p>Override this method if you want to support scroll bars.</p>
+ *
+ * <p>Read {@link RecyclerView#computeHorizontalScrollRange()} for details.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * @param state Current State of RecyclerView where you can find total item count
+ * @return The total horizontal range represented by the vertical scrollbar
+ * @see RecyclerView#computeHorizontalScrollRange()
+ */
+ public int computeHorizontalScrollRange(State state) {
+ return 0;
+ }
+
+ /**
+ * <p>Override this method if you want to support scroll bars.</p>
+ *
+ * <p>Read {@link RecyclerView#computeVerticalScrollExtent()} for details.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * @param state Current state of RecyclerView
+ * @return The vertical extent of the scrollbar's thumb
+ * @see RecyclerView#computeVerticalScrollExtent()
+ */
+ public int computeVerticalScrollExtent(State state) {
+ return 0;
+ }
+
+ /**
+ * <p>Override this method if you want to support scroll bars.</p>
+ *
+ * <p>Read {@link RecyclerView#computeVerticalScrollOffset()} for details.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * @param state Current State of RecyclerView where you can find total item count
+ * @return The vertical offset of the scrollbar's thumb
+ * @see RecyclerView#computeVerticalScrollOffset()
+ */
+ public int computeVerticalScrollOffset(State state) {
+ return 0;
+ }
+
+ /**
+ * <p>Override this method if you want to support scroll bars.</p>
+ *
+ * <p>Read {@link RecyclerView#computeVerticalScrollRange()} for details.</p>
+ *
+ * <p>Default implementation returns 0.</p>
+ *
+ * @param state Current State of RecyclerView where you can find total item count
+ * @return The total vertical range represented by the vertical scrollbar
+ * @see RecyclerView#computeVerticalScrollRange()
+ */
+ public int computeVerticalScrollRange(State state) {
+ return 0;
+ }
+
+ /**
+ * Measure the attached RecyclerView. Implementations must call
+ * {@link #setMeasuredDimension(int, int)} before returning.
+ *
+ * <p>The default implementation will handle EXACTLY measurements and respect
+ * the minimum width and height properties of the host RecyclerView if measured
+ * as UNSPECIFIED. AT_MOST measurements will be treated as EXACTLY and the RecyclerView
+ * will consume all available space.</p>
+ *
+ * @param recycler Recycler
+ * @param state Transient state of RecyclerView
+ * @param widthSpec Width {@link android.view.View.MeasureSpec}
+ * @param heightSpec Height {@link android.view.View.MeasureSpec}
+ */
+ public void onMeasure(Recycler recycler, State state, int widthSpec, int heightSpec) {
+ mRecyclerView.defaultOnMeasure(widthSpec, heightSpec);
+ }
+
+ /**
+ * {@link View#setMeasuredDimension(int, int) Set the measured dimensions} of the
+ * host RecyclerView.
+ *
+ * @param widthSize Measured width
+ * @param heightSize Measured height
+ */
+ public void setMeasuredDimension(int widthSize, int heightSize) {
+ mRecyclerView.setMeasuredDimension(widthSize, heightSize);
+ }
+
+ /**
+ * @return The host RecyclerView's {@link View#getMinimumWidth()}
+ */
+ public int getMinimumWidth() {
+ return mRecyclerView.getMinimumWidth();
+ }
+
+ /**
+ * @return The host RecyclerView's {@link View#getMinimumHeight()}
+ */
+ public int getMinimumHeight() {
+ return mRecyclerView.getMinimumHeight();
+ }
+ /**
+ * <p>Called when the LayoutManager should save its state. This is a good time to save your
+ * scroll position, configuration and anything else that may be required to restore the same
+ * layout state if the LayoutManager is recreated.</p>
+ * <p>RecyclerView does NOT verify if the LayoutManager has changed between state save and
+ * restore. This will let you share information between your LayoutManagers but it is also
+ * your responsibility to make sure they use the same parcelable class.</p>
+ *
+ * @return Necessary information for LayoutManager to be able to restore its state
+ */
+ public Parcelable onSaveInstanceState() {
+ return null;
+ }
+
+
+ public void onRestoreInstanceState(Parcelable state) {
+
+ }
+
+ void stopSmoothScroller() {
+ if (mSmoothScroller != null) {
+ mSmoothScroller.stop();
+ }
+ }
+
+ private void onSmoothScrollerStopped(SmoothScroller smoothScroller) {
+ if (mSmoothScroller == smoothScroller) {
+ mSmoothScroller = null;
+ }
+ }
+
+ /**
+ * RecyclerView calls this method to notify LayoutManager that scroll state has changed.
+ *
+ * @param state The new scroll state for RecyclerView
+ */
+ public void onScrollStateChanged(int state) {
+ }
+
+ /**
+ * Removes all views and recycles them using the given recycler.
+ * <p>
+ * If you want to clean cached views as well, you should call {@link Recycler#clear()} too.
+ * <p>
+ * If a View is marked as "ignored", it is not removed nor recycled.
+ *
+ * @param recycler Recycler to use to recycle children
+ * @see #removeAndRecycleView(View, Recycler)
+ * @see #removeAndRecycleViewAt(int, Recycler)
+ * @see #ignoreView(View)
+ */
+ public void removeAndRecycleAllViews(Recycler recycler) {
+ for (int i = getChildCount() - 1; i >= 0; i--) {
+ final View view = getChildAt(i);
+ if (!getChildViewHolderInt(view).shouldIgnore()) {
+ removeAndRecycleViewAt(i, recycler);
+ }
+ }
+ }
+
+ // called by accessibility delegate
+ void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
+ onInitializeAccessibilityNodeInfo(mRecyclerView.mRecycler, mRecyclerView.mState, info);
+ }
+
+ /**
+ * Called by the AccessibilityDelegate when the information about the current layout should
+ * be populated.
+ * <p>
+ * Default implementation adds a {@link
+ * android.view.accessibility.AccessibilityNodeInfo.CollectionInfo}.
+ * <p>
+ * You should override
+ * {@link #getRowCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)},
+ * {@link #getColumnCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)},
+ * {@link #isLayoutHierarchical(RecyclerView.Recycler, RecyclerView.State)} and
+ * {@link #getSelectionModeForAccessibility(RecyclerView.Recycler, RecyclerView.State)} for
+ * more accurate accessibility information.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @param info The info that should be filled by the LayoutManager
+ * @see View#onInitializeAccessibilityNodeInfo(
+ *android.view.accessibility.AccessibilityNodeInfo)
+ * @see #getRowCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
+ * @see #getColumnCountForAccessibility(RecyclerView.Recycler, RecyclerView.State)
+ * @see #isLayoutHierarchical(RecyclerView.Recycler, RecyclerView.State)
+ * @see #getSelectionModeForAccessibility(RecyclerView.Recycler, RecyclerView.State)
+ */
+ public void onInitializeAccessibilityNodeInfo(Recycler recycler, State state,
+ AccessibilityNodeInfo info) {
+ if (mRecyclerView.canScrollVertically(-1)
+ || mRecyclerView.canScrollHorizontally(-1)) {
+ info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD);
+ info.setScrollable(true);
+ }
+ if (mRecyclerView.canScrollVertically(1)
+ || mRecyclerView.canScrollHorizontally(1)) {
+ info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_FORWARD);
+ info.setScrollable(true);
+ }
+ final AccessibilityNodeInfo.CollectionInfo collectionInfo =
+ AccessibilityNodeInfo.CollectionInfo
+ .obtain(getRowCountForAccessibility(recycler, state),
+ getColumnCountForAccessibility(recycler, state),
+ isLayoutHierarchical(recycler, state),
+ getSelectionModeForAccessibility(recycler, state));
+ info.setCollectionInfo(collectionInfo);
+ }
+
+ // called by accessibility delegate
+ public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
+ onInitializeAccessibilityEvent(mRecyclerView.mRecycler, mRecyclerView.mState, event);
+ }
+
+ /**
+ * Called by the accessibility delegate to initialize an accessibility event.
+ * <p>
+ * Default implementation adds item count and scroll information to the event.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @param event The event instance to initialize
+ * @see View#onInitializeAccessibilityEvent(android.view.accessibility.AccessibilityEvent)
+ */
+ public void onInitializeAccessibilityEvent(Recycler recycler, State state,
+ AccessibilityEvent event) {
+ if (mRecyclerView == null || event == null) {
+ return;
+ }
+ event.setScrollable(mRecyclerView.canScrollVertically(1)
+ || mRecyclerView.canScrollVertically(-1)
+ || mRecyclerView.canScrollHorizontally(-1)
+ || mRecyclerView.canScrollHorizontally(1));
+
+ if (mRecyclerView.mAdapter != null) {
+ event.setItemCount(mRecyclerView.mAdapter.getItemCount());
+ }
+ }
+
+ // called by accessibility delegate
+ void onInitializeAccessibilityNodeInfoForItem(View host, AccessibilityNodeInfo info) {
+ final ViewHolder vh = getChildViewHolderInt(host);
+ // avoid trying to create accessibility node info for removed children
+ if (vh != null && !vh.isRemoved() && !mChildHelper.isHidden(vh.itemView)) {
+ onInitializeAccessibilityNodeInfoForItem(mRecyclerView.mRecycler,
+ mRecyclerView.mState, host, info);
+ }
+ }
+
+ /**
+ * Called by the AccessibilityDelegate when the accessibility information for a specific
+ * item should be populated.
+ * <p>
+ * Default implementation adds basic positioning information about the item.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @param host The child for which accessibility node info should be populated
+ * @param info The info to fill out about the item
+ * @see android.widget.AbsListView#onInitializeAccessibilityNodeInfoForItem(View, int,
+ * android.view.accessibility.AccessibilityNodeInfo)
+ */
+ public void onInitializeAccessibilityNodeInfoForItem(Recycler recycler, State state,
+ View host, AccessibilityNodeInfo info) {
+ int rowIndexGuess = canScrollVertically() ? getPosition(host) : 0;
+ int columnIndexGuess = canScrollHorizontally() ? getPosition(host) : 0;
+ final AccessibilityNodeInfo.CollectionItemInfo itemInfo =
+ AccessibilityNodeInfo.CollectionItemInfo.obtain(rowIndexGuess, 1,
+ columnIndexGuess, 1, false, false);
+ info.setCollectionItemInfo(itemInfo);
+ }
+
+ /**
+ * A LayoutManager can call this method to force RecyclerView to run simple animations in
+ * the next layout pass, even if there is not any trigger to do so. (e.g. adapter data
+ * change).
+ * <p>
+ * Note that, calling this method will not guarantee that RecyclerView will run animations
+ * at all. For example, if there is not any {@link ItemAnimator} set, RecyclerView will
+ * not run any animations but will still clear this flag after the layout is complete.
+ *
+ */
+ public void requestSimpleAnimationsInNextLayout() {
+ mRequestedSimpleAnimations = true;
+ }
+
+ /**
+ * Returns the selection mode for accessibility. Should be
+ * {@link AccessibilityNodeInfo.CollectionInfo#SELECTION_MODE_NONE},
+ * {@link AccessibilityNodeInfo.CollectionInfo#SELECTION_MODE_SINGLE} or
+ * {@link AccessibilityNodeInfo.CollectionInfo#SELECTION_MODE_MULTIPLE}.
+ * <p>
+ * Default implementation returns
+ * {@link AccessibilityNodeInfo.CollectionInfo#SELECTION_MODE_NONE}.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @return Selection mode for accessibility. Default implementation returns
+ * {@link AccessibilityNodeInfo.CollectionInfo#SELECTION_MODE_NONE}.
+ */
+ public int getSelectionModeForAccessibility(Recycler recycler, State state) {
+ return AccessibilityNodeInfo.CollectionInfo.SELECTION_MODE_NONE;
+ }
+
+ /**
+ * Returns the number of rows for accessibility.
+ * <p>
+ * Default implementation returns the number of items in the adapter if LayoutManager
+ * supports vertical scrolling or 1 if LayoutManager does not support vertical
+ * scrolling.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @return The number of rows in LayoutManager for accessibility.
+ */
+ public int getRowCountForAccessibility(Recycler recycler, State state) {
+ if (mRecyclerView == null || mRecyclerView.mAdapter == null) {
+ return 1;
+ }
+ return canScrollVertically() ? mRecyclerView.mAdapter.getItemCount() : 1;
+ }
+
+ /**
+ * Returns the number of columns for accessibility.
+ * <p>
+ * Default implementation returns the number of items in the adapter if LayoutManager
+ * supports horizontal scrolling or 1 if LayoutManager does not support horizontal
+ * scrolling.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @return The number of rows in LayoutManager for accessibility.
+ */
+ public int getColumnCountForAccessibility(Recycler recycler, State state) {
+ if (mRecyclerView == null || mRecyclerView.mAdapter == null) {
+ return 1;
+ }
+ return canScrollHorizontally() ? mRecyclerView.mAdapter.getItemCount() : 1;
+ }
+
+ /**
+ * Returns whether layout is hierarchical or not to be used for accessibility.
+ * <p>
+ * Default implementation returns false.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @return True if layout is hierarchical.
+ */
+ public boolean isLayoutHierarchical(Recycler recycler, State state) {
+ return false;
+ }
+
+ // called by accessibility delegate
+ boolean performAccessibilityAction(int action, Bundle args) {
+ return performAccessibilityAction(mRecyclerView.mRecycler, mRecyclerView.mState,
+ action, args);
+ }
+
+ /**
+ * Called by AccessibilityDelegate when an action is requested from the RecyclerView.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @param action The action to perform
+ * @param args Optional action arguments
+ * @see View#performAccessibilityAction(int, android.os.Bundle)
+ */
+ public boolean performAccessibilityAction(Recycler recycler, State state, int action,
+ Bundle args) {
+ if (mRecyclerView == null) {
+ return false;
+ }
+ int vScroll = 0, hScroll = 0;
+ switch (action) {
+ case AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD:
+ if (mRecyclerView.canScrollVertically(-1)) {
+ vScroll = -(getHeight() - getPaddingTop() - getPaddingBottom());
+ }
+ if (mRecyclerView.canScrollHorizontally(-1)) {
+ hScroll = -(getWidth() - getPaddingLeft() - getPaddingRight());
+ }
+ break;
+ case AccessibilityNodeInfo.ACTION_SCROLL_FORWARD:
+ if (mRecyclerView.canScrollVertically(1)) {
+ vScroll = getHeight() - getPaddingTop() - getPaddingBottom();
+ }
+ if (mRecyclerView.canScrollHorizontally(1)) {
+ hScroll = getWidth() - getPaddingLeft() - getPaddingRight();
+ }
+ break;
+ }
+ if (vScroll == 0 && hScroll == 0) {
+ return false;
+ }
+ mRecyclerView.scrollBy(hScroll, vScroll);
+ return true;
+ }
+
+ // called by accessibility delegate
+ boolean performAccessibilityActionForItem(View view, int action, Bundle args) {
+ return performAccessibilityActionForItem(mRecyclerView.mRecycler, mRecyclerView.mState,
+ view, action, args);
+ }
+
+ /**
+ * Called by AccessibilityDelegate when an accessibility action is requested on one of the
+ * children of LayoutManager.
+ * <p>
+ * Default implementation does not do anything.
+ *
+ * @param recycler The Recycler that can be used to convert view positions into adapter
+ * positions
+ * @param state The current state of RecyclerView
+ * @param view The child view on which the action is performed
+ * @param action The action to perform
+ * @param args Optional action arguments
+ * @return true if action is handled
+ * @see View#performAccessibilityAction(int, android.os.Bundle)
+ */
+ public boolean performAccessibilityActionForItem(Recycler recycler, State state, View view,
+ int action, Bundle args) {
+ return false;
+ }
+
+ /**
+ * Parse the xml attributes to get the most common properties used by layout managers.
+ *
+ * @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_android_orientation
+ * @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_spanCount
+ * @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_reverseLayout
+ * @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_stackFromEnd
+ *
+ * @return an object containing the properties as specified in the attrs.
+ */
+ public static Properties getProperties(Context context, AttributeSet attrs,
+ int defStyleAttr, int defStyleRes) {
+ Properties properties = new Properties();
+ TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RecyclerView,
+ defStyleAttr, defStyleRes);
+ properties.orientation = a.getInt(R.styleable.RecyclerView_orientation, VERTICAL);
+ properties.spanCount = a.getInt(R.styleable.RecyclerView_spanCount, 1);
+ properties.reverseLayout = a.getBoolean(R.styleable.RecyclerView_reverseLayout, false);
+ properties.stackFromEnd = a.getBoolean(R.styleable.RecyclerView_stackFromEnd, false);
+ a.recycle();
+ return properties;
+ }
+
+ void setExactMeasureSpecsFrom(RecyclerView recyclerView) {
+ setMeasureSpecs(
+ MeasureSpec.makeMeasureSpec(recyclerView.getWidth(), MeasureSpec.EXACTLY),
+ MeasureSpec.makeMeasureSpec(recyclerView.getHeight(), MeasureSpec.EXACTLY)
+ );
+ }
+
+ /**
+ * Internal API to allow LayoutManagers to be measured twice.
+ * <p>
+ * This is not public because LayoutManagers should be able to handle their layouts in one
+ * pass but it is very convenient to make existing LayoutManagers support wrapping content
+ * when both orientations are undefined.
+ * <p>
+ * This API will be removed after default LayoutManagers properly implement wrap content in
+ * non-scroll orientation.
+ */
+ boolean shouldMeasureTwice() {
+ return false;
+ }
+
+ boolean hasFlexibleChildInBothOrientations() {
+ final int childCount = getChildCount();
+ for (int i = 0; i < childCount; i++) {
+ final View child = getChildAt(i);
+ final ViewGroup.LayoutParams lp = child.getLayoutParams();
+ if (lp.width < 0 && lp.height < 0) {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Some general properties that a LayoutManager may want to use.
+ */
+ public static class Properties {
+ /** @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_android_orientation */
+ public int orientation;
+ /** @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_spanCount */
+ public int spanCount;
+ /** @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_reverseLayout */
+ public boolean reverseLayout;
+ /** @attr ref android.support.v7.recyclerview.R.styleable#RecyclerView_stackFromEnd */
+ public boolean stackFromEnd;
+ }
+ }
+
+ /**
+ * An ItemDecoration allows the application to add a special drawing and layout offset
+ * to specific item views from the adapter's data set. This can be useful for drawing dividers
+ * between items, highlights, visual grouping boundaries and more.
+ *
+ * <p>All ItemDecorations are drawn in the order they were added, before the item
+ * views (in {@link ItemDecoration#onDraw(Canvas, RecyclerView, RecyclerView.State) onDraw()}
+ * and after the items (in {@link ItemDecoration#onDrawOver(Canvas, RecyclerView,
+ * RecyclerView.State)}.</p>
+ */
+ public abstract static class ItemDecoration {
+ /**
+ * Draw any appropriate decorations into the Canvas supplied to the RecyclerView.
+ * Any content drawn by this method will be drawn before the item views are drawn,
+ * and will thus appear underneath the views.
+ *
+ * @param c Canvas to draw into
+ * @param parent RecyclerView this ItemDecoration is drawing into
+ * @param state The current state of RecyclerView
+ */
+ public void onDraw(Canvas c, RecyclerView parent, State state) {
+ onDraw(c, parent);
+ }
+
+ /**
+ * @deprecated
+ * Override {@link #onDraw(Canvas, RecyclerView, RecyclerView.State)}
+ */
+ @Deprecated
+ public void onDraw(Canvas c, RecyclerView parent) {
+ }
+
+ /**
+ * Draw any appropriate decorations into the Canvas supplied to the RecyclerView.
+ * Any content drawn by this method will be drawn after the item views are drawn
+ * and will thus appear over the views.
+ *
+ * @param c Canvas to draw into
+ * @param parent RecyclerView this ItemDecoration is drawing into
+ * @param state The current state of RecyclerView.
+ */
+ public void onDrawOver(Canvas c, RecyclerView parent, State state) {
+ onDrawOver(c, parent);
+ }
+
+ /**
+ * @deprecated
+ * Override {@link #onDrawOver(Canvas, RecyclerView, RecyclerView.State)}
+ */
+ @Deprecated
+ public void onDrawOver(Canvas c, RecyclerView parent) {
+ }
+
+
+ /**
+ * @deprecated
+ * Use {@link #getItemOffsets(Rect, View, RecyclerView, State)}
+ */
+ @Deprecated
+ public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
+ outRect.set(0, 0, 0, 0);
+ }
+
+ /**
+ * Retrieve any offsets for the given item. Each field of <code>outRect</code> specifies
+ * the number of pixels that the item view should be inset by, similar to padding or margin.
+ * The default implementation sets the bounds of outRect to 0 and returns.
+ *
+ * <p>
+ * If this ItemDecoration does not affect the positioning of item views, it should set
+ * all four fields of <code>outRect</code> (left, top, right, bottom) to zero
+ * before returning.
+ *
+ * <p>
+ * If you need to access Adapter for additional data, you can call
+ * {@link RecyclerView#getChildAdapterPosition(View)} to get the adapter position of the
+ * View.
+ *
+ * @param outRect Rect to receive the output.
+ * @param view The child view to decorate
+ * @param parent RecyclerView this ItemDecoration is decorating
+ * @param state The current state of RecyclerView.
+ */
+ public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {
+ getItemOffsets(outRect, ((LayoutParams) view.getLayoutParams()).getViewLayoutPosition(),
+ parent);
+ }
+ }
+
+ /**
+ * An OnItemTouchListener allows the application to intercept touch events in progress at the
+ * view hierarchy level of the RecyclerView before those touch events are considered for
+ * RecyclerView's own scrolling behavior.
+ *
+ * <p>This can be useful for applications that wish to implement various forms of gestural
+ * manipulation of item views within the RecyclerView. OnItemTouchListeners may intercept
+ * a touch interaction already in progress even if the RecyclerView is already handling that
+ * gesture stream itself for the purposes of scrolling.</p>
+ *
+ * @see SimpleOnItemTouchListener
+ */
+ public interface OnItemTouchListener {
+ /**
+ * Silently observe and/or take over touch events sent to the RecyclerView
+ * before they are handled by either the RecyclerView itself or its child views.
+ *
+ * <p>The onInterceptTouchEvent methods of each attached OnItemTouchListener will be run
+ * in the order in which each listener was added, before any other touch processing
+ * by the RecyclerView itself or child views occurs.</p>
+ *
+ * @param e MotionEvent describing the touch event. All coordinates are in
+ * the RecyclerView's coordinate system.
+ * @return true if this OnItemTouchListener wishes to begin intercepting touch events, false
+ * to continue with the current behavior and continue observing future events in
+ * the gesture.
+ */
+ boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e);
+
+ /**
+ * Process a touch event as part of a gesture that was claimed by returning true from
+ * a previous call to {@link #onInterceptTouchEvent}.
+ *
+ * @param e MotionEvent describing the touch event. All coordinates are in
+ * the RecyclerView's coordinate system.
+ */
+ void onTouchEvent(RecyclerView rv, MotionEvent e);
+
+ /**
+ * Called when a child of RecyclerView does not want RecyclerView and its ancestors to
+ * intercept touch events with
+ * {@link ViewGroup#onInterceptTouchEvent(MotionEvent)}.
+ *
+ * @param disallowIntercept True if the child does not want the parent to
+ * intercept touch events.
+ * @see ViewParent#requestDisallowInterceptTouchEvent(boolean)
+ */
+ void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept);
+ }
+
+ /**
+ * An implementation of {@link RecyclerView.OnItemTouchListener} that has empty method bodies
+ * and default return values.
+ * <p>
+ * You may prefer to extend this class if you don't need to override all methods. Another
+ * benefit of using this class is future compatibility. As the interface may change, we'll
+ * always provide a default implementation on this class so that your code won't break when
+ * you update to a new version of the support library.
+ */
+ public static class SimpleOnItemTouchListener implements RecyclerView.OnItemTouchListener {
+ @Override
+ public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
+ return false;
+ }
+
+ @Override
+ public void onTouchEvent(RecyclerView rv, MotionEvent e) {
+ }
+
+ @Override
+ public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
+ }
+ }
+
+
+ /**
+ * An OnScrollListener can be added to a RecyclerView to receive messages when a scrolling event
+ * has occurred on that RecyclerView.
+ * <p>
+ * @see RecyclerView#addOnScrollListener(OnScrollListener)
+ * @see RecyclerView#clearOnChildAttachStateChangeListeners()
+ *
+ */
+ public abstract static class OnScrollListener {
+ /**
+ * Callback method to be invoked when RecyclerView's scroll state changes.
+ *
+ * @param recyclerView The RecyclerView whose scroll state has changed.
+ * @param newState The updated scroll state. One of {@link #SCROLL_STATE_IDLE},
+ * {@link #SCROLL_STATE_DRAGGING} or {@link #SCROLL_STATE_SETTLING}.
+ */
+ public void onScrollStateChanged(RecyclerView recyclerView, int newState){}
+
+ /**
+ * Callback method to be invoked when the RecyclerView has been scrolled. This will be
+ * called after the scroll has completed.
+ * <p>
+ * This callback will also be called if visible item range changes after a layout
+ * calculation. In that case, dx and dy will be 0.
+ *
+ * @param recyclerView The RecyclerView which scrolled.
+ * @param dx The amount of horizontal scroll.
+ * @param dy The amount of vertical scroll.
+ */
+ public void onScrolled(RecyclerView recyclerView, int dx, int dy){}
+ }
+
+ /**
+ * A RecyclerListener can be set on a RecyclerView to receive messages whenever
+ * a view is recycled.
+ *
+ * @see RecyclerView#setRecyclerListener(RecyclerListener)
+ */
+ public interface RecyclerListener {
+
+ /**
+ * This method is called whenever the view in the ViewHolder is recycled.
+ *
+ * RecyclerView calls this method right before clearing ViewHolder's internal data and
+ * sending it to RecycledViewPool. This way, if ViewHolder was holding valid information
+ * before being recycled, you can call {@link ViewHolder#getAdapterPosition()} to get
+ * its adapter position.
+ *
+ * @param holder The ViewHolder containing the view that was recycled
+ */
+ void onViewRecycled(ViewHolder holder);
+ }
+
+ /**
+ * A Listener interface that can be attached to a RecylcerView to get notified
+ * whenever a ViewHolder is attached to or detached from RecyclerView.
+ */
+ public interface OnChildAttachStateChangeListener {
+
+ /**
+ * Called when a view is attached to the RecyclerView.
+ *
+ * @param view The View which is attached to the RecyclerView
+ */
+ void onChildViewAttachedToWindow(View view);
+
+ /**
+ * Called when a view is detached from RecyclerView.
+ *
+ * @param view The View which is being detached from the RecyclerView
+ */
+ void onChildViewDetachedFromWindow(View view);
+ }
+
+ /**
+ * A ViewHolder describes an item view and metadata about its place within the RecyclerView.
+ *
+ * <p>{@link Adapter} implementations should subclass ViewHolder and add fields for caching
+ * potentially expensive {@link View#findViewById(int)} results.</p>
+ *
+ * <p>While {@link LayoutParams} belong to the {@link LayoutManager},
+ * {@link ViewHolder ViewHolders} belong to the adapter. Adapters should feel free to use
+ * their own custom ViewHolder implementations to store data that makes binding view contents
+ * easier. Implementations should assume that individual item views will hold strong references
+ * to <code>ViewHolder</code> objects and that <code>RecyclerView</code> instances may hold
+ * strong references to extra off-screen item views for caching purposes</p>
+ */
+ public abstract static class ViewHolder {
+ public final View itemView;
+ WeakReference<RecyclerView> mNestedRecyclerView;
+ int mPosition = NO_POSITION;
+ int mOldPosition = NO_POSITION;
+ long mItemId = NO_ID;
+ int mItemViewType = INVALID_TYPE;
+ int mPreLayoutPosition = NO_POSITION;
+
+ // The item that this holder is shadowing during an item change event/animation
+ ViewHolder mShadowedHolder = null;
+ // The item that is shadowing this holder during an item change event/animation
+ ViewHolder mShadowingHolder = null;
+
+ /**
+ * This ViewHolder has been bound to a position; mPosition, mItemId and mItemViewType
+ * are all valid.
+ */
+ static final int FLAG_BOUND = 1 << 0;
+
+ /**
+ * The data this ViewHolder's view reflects is stale and needs to be rebound
+ * by the adapter. mPosition and mItemId are consistent.
+ */
+ static final int FLAG_UPDATE = 1 << 1;
+
+ /**
+ * This ViewHolder's data is invalid. The identity implied by mPosition and mItemId
+ * are not to be trusted and may no longer match the item view type.
+ * This ViewHolder must be fully rebound to different data.
+ */
+ static final int FLAG_INVALID = 1 << 2;
+
+ /**
+ * This ViewHolder points at data that represents an item previously removed from the
+ * data set. Its view may still be used for things like outgoing animations.
+ */
+ static final int FLAG_REMOVED = 1 << 3;
+
+ /**
+ * This ViewHolder should not be recycled. This flag is set via setIsRecyclable()
+ * and is intended to keep views around during animations.
+ */
+ static final int FLAG_NOT_RECYCLABLE = 1 << 4;
+
+ /**
+ * This ViewHolder is returned from scrap which means we are expecting an addView call
+ * for this itemView. When returned from scrap, ViewHolder stays in the scrap list until
+ * the end of the layout pass and then recycled by RecyclerView if it is not added back to
+ * the RecyclerView.
+ */
+ static final int FLAG_RETURNED_FROM_SCRAP = 1 << 5;
+
+ /**
+ * This ViewHolder is fully managed by the LayoutManager. We do not scrap, recycle or remove
+ * it unless LayoutManager is replaced.
+ * It is still fully visible to the LayoutManager.
+ */
+ static final int FLAG_IGNORE = 1 << 7;
+
+ /**
+ * When the View is detached form the parent, we set this flag so that we can take correct
+ * action when we need to remove it or add it back.
+ */
+ static final int FLAG_TMP_DETACHED = 1 << 8;
+
+ /**
+ * Set when we can no longer determine the adapter position of this ViewHolder until it is
+ * rebound to a new position. It is different than FLAG_INVALID because FLAG_INVALID is
+ * set even when the type does not match. Also, FLAG_ADAPTER_POSITION_UNKNOWN is set as soon
+ * as adapter notification arrives vs FLAG_INVALID is set lazily before layout is
+ * re-calculated.
+ */
+ static final int FLAG_ADAPTER_POSITION_UNKNOWN = 1 << 9;
+
+ /**
+ * Set when a addChangePayload(null) is called
+ */
+ static final int FLAG_ADAPTER_FULLUPDATE = 1 << 10;
+
+ /**
+ * Used by ItemAnimator when a ViewHolder's position changes
+ */
+ static final int FLAG_MOVED = 1 << 11;
+
+ /**
+ * Used by ItemAnimator when a ViewHolder appears in pre-layout
+ */
+ static final int FLAG_APPEARED_IN_PRE_LAYOUT = 1 << 12;
+
+ static final int PENDING_ACCESSIBILITY_STATE_NOT_SET = -1;
+
+ /**
+ * Used when a ViewHolder starts the layout pass as a hidden ViewHolder but is re-used from
+ * hidden list (as if it was scrap) without being recycled in between.
+ *
+ * When a ViewHolder is hidden, there are 2 paths it can be re-used:
+ * a) Animation ends, view is recycled and used from the recycle pool.
+ * b) LayoutManager asks for the View for that position while the ViewHolder is hidden.
+ *
+ * This flag is used to represent "case b" where the ViewHolder is reused without being
+ * recycled (thus "bounced" from the hidden list). This state requires special handling
+ * because the ViewHolder must be added to pre layout maps for animations as if it was
+ * already there.
+ */
+ static final int FLAG_BOUNCED_FROM_HIDDEN_LIST = 1 << 13;
+
+ private int mFlags;
+
+ private static final List<Object> FULLUPDATE_PAYLOADS = Collections.EMPTY_LIST;
+
+ List<Object> mPayloads = null;
+ List<Object> mUnmodifiedPayloads = null;
+
+ private int mIsRecyclableCount = 0;
+
+ // If non-null, view is currently considered scrap and may be reused for other data by the
+ // scrap container.
+ private Recycler mScrapContainer = null;
+ // Keeps whether this ViewHolder lives in Change scrap or Attached scrap
+ private boolean mInChangeScrap = false;
+
+ // Saves isImportantForAccessibility value for the view item while it's in hidden state and
+ // marked as unimportant for accessibility.
+ private int mWasImportantForAccessibilityBeforeHidden =
+ View.IMPORTANT_FOR_ACCESSIBILITY_AUTO;
+ // set if we defer the accessibility state change of the view holder
+ @VisibleForTesting
+ int mPendingAccessibilityState = PENDING_ACCESSIBILITY_STATE_NOT_SET;
+
+ /**
+ * Is set when VH is bound from the adapter and cleaned right before it is sent to
+ * {@link RecycledViewPool}.
+ */
+ RecyclerView mOwnerRecyclerView;
+
+ public ViewHolder(View itemView) {
+ if (itemView == null) {
+ throw new IllegalArgumentException("itemView may not be null");
+ }
+ this.itemView = itemView;
+ }
+
+ void flagRemovedAndOffsetPosition(int mNewPosition, int offset, boolean applyToPreLayout) {
+ addFlags(ViewHolder.FLAG_REMOVED);
+ offsetPosition(offset, applyToPreLayout);
+ mPosition = mNewPosition;
+ }
+
+ void offsetPosition(int offset, boolean applyToPreLayout) {
+ if (mOldPosition == NO_POSITION) {
+ mOldPosition = mPosition;
+ }
+ if (mPreLayoutPosition == NO_POSITION) {
+ mPreLayoutPosition = mPosition;
+ }
+ if (applyToPreLayout) {
+ mPreLayoutPosition += offset;
+ }
+ mPosition += offset;
+ if (itemView.getLayoutParams() != null) {
+ ((LayoutParams) itemView.getLayoutParams()).mInsetsDirty = true;
+ }
+ }
+
+ void clearOldPosition() {
+ mOldPosition = NO_POSITION;
+ mPreLayoutPosition = NO_POSITION;
+ }
+
+ void saveOldPosition() {
+ if (mOldPosition == NO_POSITION) {
+ mOldPosition = mPosition;
+ }
+ }
+
+ boolean shouldIgnore() {
+ return (mFlags & FLAG_IGNORE) != 0;
+ }
+
+ /**
+ * @deprecated This method is deprecated because its meaning is ambiguous due to the async
+ * handling of adapter updates. Please use {@link #getLayoutPosition()} or
+ * {@link #getAdapterPosition()} depending on your use case.
+ *
+ * @see #getLayoutPosition()
+ * @see #getAdapterPosition()
+ */
+ @Deprecated
+ public final int getPosition() {
+ return mPreLayoutPosition == NO_POSITION ? mPosition : mPreLayoutPosition;
+ }
+
+ /**
+ * Returns the position of the ViewHolder in terms of the latest layout pass.
+ * <p>
+ * This position is mostly used by RecyclerView components to be consistent while
+ * RecyclerView lazily processes adapter updates.
+ * <p>
+ * For performance and animation reasons, RecyclerView batches all adapter updates until the
+ * next layout pass. This may cause mismatches between the Adapter position of the item and
+ * the position it had in the latest layout calculations.
+ * <p>
+ * LayoutManagers should always call this method while doing calculations based on item
+ * positions. All methods in {@link RecyclerView.LayoutManager}, {@link RecyclerView.State},
+ * {@link RecyclerView.Recycler} that receive a position expect it to be the layout position
+ * of the item.
+ * <p>
+ * If LayoutManager needs to call an external method that requires the adapter position of
+ * the item, it can use {@link #getAdapterPosition()} or
+ * {@link RecyclerView.Recycler#convertPreLayoutPositionToPostLayout(int)}.
+ *
+ * @return Returns the adapter position of the ViewHolder in the latest layout pass.
+ * @see #getAdapterPosition()
+ */
+ public final int getLayoutPosition() {
+ return mPreLayoutPosition == NO_POSITION ? mPosition : mPreLayoutPosition;
+ }
+
+ /**
+ * Returns the Adapter position of the item represented by this ViewHolder.
+ * <p>
+ * Note that this might be different than the {@link #getLayoutPosition()} if there are
+ * pending adapter updates but a new layout pass has not happened yet.
+ * <p>
+ * RecyclerView does not handle any adapter updates until the next layout traversal. This
+ * may create temporary inconsistencies between what user sees on the screen and what
+ * adapter contents have. This inconsistency is not important since it will be less than
+ * 16ms but it might be a problem if you want to use ViewHolder position to access the
+ * adapter. Sometimes, you may need to get the exact adapter position to do
+ * some actions in response to user events. In that case, you should use this method which
+ * will calculate the Adapter position of the ViewHolder.
+ * <p>
+ * Note that if you've called {@link RecyclerView.Adapter#notifyDataSetChanged()}, until the
+ * next layout pass, the return value of this method will be {@link #NO_POSITION}.
+ *
+ * @return The adapter position of the item if it still exists in the adapter.
+ * {@link RecyclerView#NO_POSITION} if item has been removed from the adapter,
+ * {@link RecyclerView.Adapter#notifyDataSetChanged()} has been called after the last
+ * layout pass or the ViewHolder has already been recycled.
+ */
+ public final int getAdapterPosition() {
+ if (mOwnerRecyclerView == null) {
+ return NO_POSITION;
+ }
+ return mOwnerRecyclerView.getAdapterPositionFor(this);
+ }
+
+ /**
+ * When LayoutManager supports animations, RecyclerView tracks 3 positions for ViewHolders
+ * to perform animations.
+ * <p>
+ * If a ViewHolder was laid out in the previous onLayout call, old position will keep its
+ * adapter index in the previous layout.
+ *
+ * @return The previous adapter index of the Item represented by this ViewHolder or
+ * {@link #NO_POSITION} if old position does not exists or cleared (pre-layout is
+ * complete).
+ */
+ public final int getOldPosition() {
+ return mOldPosition;
+ }
+
+ /**
+ * Returns The itemId represented by this ViewHolder.
+ *
+ * @return The item's id if adapter has stable ids, {@link RecyclerView#NO_ID}
+ * otherwise
+ */
+ public final long getItemId() {
+ return mItemId;
+ }
+
+ /**
+ * @return The view type of this ViewHolder.
+ */
+ public final int getItemViewType() {
+ return mItemViewType;
+ }
+
+ boolean isScrap() {
+ return mScrapContainer != null;
+ }
+
+ void unScrap() {
+ mScrapContainer.unscrapView(this);
+ }
+
+ boolean wasReturnedFromScrap() {
+ return (mFlags & FLAG_RETURNED_FROM_SCRAP) != 0;
+ }
+
+ void clearReturnedFromScrapFlag() {
+ mFlags = mFlags & ~FLAG_RETURNED_FROM_SCRAP;
+ }
+
+ void clearTmpDetachFlag() {
+ mFlags = mFlags & ~FLAG_TMP_DETACHED;
+ }
+
+ void stopIgnoring() {
+ mFlags = mFlags & ~FLAG_IGNORE;
+ }
+
+ void setScrapContainer(Recycler recycler, boolean isChangeScrap) {
+ mScrapContainer = recycler;
+ mInChangeScrap = isChangeScrap;
+ }
+
+ boolean isInvalid() {
+ return (mFlags & FLAG_INVALID) != 0;
+ }
+
+ boolean needsUpdate() {
+ return (mFlags & FLAG_UPDATE) != 0;
+ }
+
+ boolean isBound() {
+ return (mFlags & FLAG_BOUND) != 0;
+ }
+
+ boolean isRemoved() {
+ return (mFlags & FLAG_REMOVED) != 0;
+ }
+
+ boolean hasAnyOfTheFlags(int flags) {
+ return (mFlags & flags) != 0;
+ }
+
+ boolean isTmpDetached() {
+ return (mFlags & FLAG_TMP_DETACHED) != 0;
+ }
+
+ boolean isAdapterPositionUnknown() {
+ return (mFlags & FLAG_ADAPTER_POSITION_UNKNOWN) != 0 || isInvalid();
+ }
+
+ void setFlags(int flags, int mask) {
+ mFlags = (mFlags & ~mask) | (flags & mask);
+ }
+
+ void addFlags(int flags) {
+ mFlags |= flags;
+ }
+
+ void addChangePayload(Object payload) {
+ if (payload == null) {
+ addFlags(FLAG_ADAPTER_FULLUPDATE);
+ } else if ((mFlags & FLAG_ADAPTER_FULLUPDATE) == 0) {
+ createPayloadsIfNeeded();
+ mPayloads.add(payload);
+ }
+ }
+
+ private void createPayloadsIfNeeded() {
+ if (mPayloads == null) {
+ mPayloads = new ArrayList<Object>();
+ mUnmodifiedPayloads = Collections.unmodifiableList(mPayloads);
+ }
+ }
+
+ void clearPayload() {
+ if (mPayloads != null) {
+ mPayloads.clear();
+ }
+ mFlags = mFlags & ~FLAG_ADAPTER_FULLUPDATE;
+ }
+
+ List<Object> getUnmodifiedPayloads() {
+ if ((mFlags & FLAG_ADAPTER_FULLUPDATE) == 0) {
+ if (mPayloads == null || mPayloads.size() == 0) {
+ // Initial state, no update being called.
+ return FULLUPDATE_PAYLOADS;
+ }
+ // there are none-null payloads
+ return mUnmodifiedPayloads;
+ } else {
+ // a full update has been called.
+ return FULLUPDATE_PAYLOADS;
+ }
+ }
+
+ void resetInternal() {
+ mFlags = 0;
+ mPosition = NO_POSITION;
+ mOldPosition = NO_POSITION;
+ mItemId = NO_ID;
+ mPreLayoutPosition = NO_POSITION;
+ mIsRecyclableCount = 0;
+ mShadowedHolder = null;
+ mShadowingHolder = null;
+ clearPayload();
+ mWasImportantForAccessibilityBeforeHidden = View.IMPORTANT_FOR_ACCESSIBILITY_AUTO;
+ mPendingAccessibilityState = PENDING_ACCESSIBILITY_STATE_NOT_SET;
+ clearNestedRecyclerViewIfNotNested(this);
+ }
+
+ /**
+ * Called when the child view enters the hidden state
+ */
+ private void onEnteredHiddenState(RecyclerView parent) {
+ // While the view item is in hidden state, make it invisible for the accessibility.
+ mWasImportantForAccessibilityBeforeHidden =
+ itemView.getImportantForAccessibility();
+ parent.setChildImportantForAccessibilityInternal(this,
+ View.IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS);
+ }
+
+ /**
+ * Called when the child view leaves the hidden state
+ */
+ private void onLeftHiddenState(RecyclerView parent) {
+ parent.setChildImportantForAccessibilityInternal(this,
+ mWasImportantForAccessibilityBeforeHidden);
+ mWasImportantForAccessibilityBeforeHidden = View.IMPORTANT_FOR_ACCESSIBILITY_AUTO;
+ }
+
+ @Override
+ public String toString() {
+ final StringBuilder sb = new StringBuilder("ViewHolder{"
+ + Integer.toHexString(hashCode()) + " position=" + mPosition + " id=" + mItemId
+ + ", oldPos=" + mOldPosition + ", pLpos:" + mPreLayoutPosition);
+ if (isScrap()) {
+ sb.append(" scrap ")
+ .append(mInChangeScrap ? "[changeScrap]" : "[attachedScrap]");
+ }
+ if (isInvalid()) sb.append(" invalid");
+ if (!isBound()) sb.append(" unbound");
+ if (needsUpdate()) sb.append(" update");
+ if (isRemoved()) sb.append(" removed");
+ if (shouldIgnore()) sb.append(" ignored");
+ if (isTmpDetached()) sb.append(" tmpDetached");
+ if (!isRecyclable()) sb.append(" not recyclable(" + mIsRecyclableCount + ")");
+ if (isAdapterPositionUnknown()) sb.append(" undefined adapter position");
+
+ if (itemView.getParent() == null) sb.append(" no parent");
+ sb.append("}");
+ return sb.toString();
+ }
+
+ /**
+ * Informs the recycler whether this item can be recycled. Views which are not
+ * recyclable will not be reused for other items until setIsRecyclable() is
+ * later set to true. Calls to setIsRecyclable() should always be paired (one
+ * call to setIsRecyclabe(false) should always be matched with a later call to
+ * setIsRecyclable(true)). Pairs of calls may be nested, as the state is internally
+ * reference-counted.
+ *
+ * @param recyclable Whether this item is available to be recycled. Default value
+ * is true.
+ *
+ * @see #isRecyclable()
+ */
+ public final void setIsRecyclable(boolean recyclable) {
+ mIsRecyclableCount = recyclable ? mIsRecyclableCount - 1 : mIsRecyclableCount + 1;
+ if (mIsRecyclableCount < 0) {
+ mIsRecyclableCount = 0;
+ if (DEBUG) {
+ throw new RuntimeException("isRecyclable decremented below 0: "
+ + "unmatched pair of setIsRecyable() calls for " + this);
+ }
+ Log.e(VIEW_LOG_TAG, "isRecyclable decremented below 0: "
+ + "unmatched pair of setIsRecyable() calls for " + this);
+ } else if (!recyclable && mIsRecyclableCount == 1) {
+ mFlags |= FLAG_NOT_RECYCLABLE;
+ } else if (recyclable && mIsRecyclableCount == 0) {
+ mFlags &= ~FLAG_NOT_RECYCLABLE;
+ }
+ if (DEBUG) {
+ Log.d(TAG, "setIsRecyclable val:" + recyclable + ":" + this);
+ }
+ }
+
+ /**
+ * @return true if this item is available to be recycled, false otherwise.
+ *
+ * @see #setIsRecyclable(boolean)
+ */
+ public final boolean isRecyclable() {
+ return (mFlags & FLAG_NOT_RECYCLABLE) == 0
+ && !itemView.hasTransientState();
+ }
+
+ /**
+ * Returns whether we have animations referring to this view holder or not.
+ * This is similar to isRecyclable flag but does not check transient state.
+ */
+ private boolean shouldBeKeptAsChild() {
+ return (mFlags & FLAG_NOT_RECYCLABLE) != 0;
+ }
+
+ /**
+ * @return True if ViewHolder is not referenced by RecyclerView animations but has
+ * transient state which will prevent it from being recycled.
+ */
+ private boolean doesTransientStatePreventRecycling() {
+ return (mFlags & FLAG_NOT_RECYCLABLE) == 0 && itemView.hasTransientState();
+ }
+
+ boolean isUpdated() {
+ return (mFlags & FLAG_UPDATE) != 0;
+ }
+ }
+
+ /**
+ * This method is here so that we can control the important for a11y changes and test it.
+ */
+ @VisibleForTesting
+ boolean setChildImportantForAccessibilityInternal(ViewHolder viewHolder,
+ int importantForAccessibility) {
+ if (isComputingLayout()) {
+ viewHolder.mPendingAccessibilityState = importantForAccessibility;
+ mPendingAccessibilityImportanceChange.add(viewHolder);
+ return false;
+ }
+ viewHolder.itemView.setImportantForAccessibility(importantForAccessibility);
+ return true;
+ }
+
+ void dispatchPendingImportantForAccessibilityChanges() {
+ for (int i = mPendingAccessibilityImportanceChange.size() - 1; i >= 0; i--) {
+ ViewHolder viewHolder = mPendingAccessibilityImportanceChange.get(i);
+ if (viewHolder.itemView.getParent() != this || viewHolder.shouldIgnore()) {
+ continue;
+ }
+ int state = viewHolder.mPendingAccessibilityState;
+ if (state != ViewHolder.PENDING_ACCESSIBILITY_STATE_NOT_SET) {
+ //noinspection WrongConstant
+ viewHolder.itemView.setImportantForAccessibility(state);
+ viewHolder.mPendingAccessibilityState =
+ ViewHolder.PENDING_ACCESSIBILITY_STATE_NOT_SET;
+ }
+ }
+ mPendingAccessibilityImportanceChange.clear();
+ }
+
+ int getAdapterPositionFor(ViewHolder viewHolder) {
+ if (viewHolder.hasAnyOfTheFlags(ViewHolder.FLAG_INVALID
+ | ViewHolder.FLAG_REMOVED | ViewHolder.FLAG_ADAPTER_POSITION_UNKNOWN)
+ || !viewHolder.isBound()) {
+ return RecyclerView.NO_POSITION;
+ }
+ return mAdapterHelper.applyPendingUpdatesToPosition(viewHolder.mPosition);
+ }
+
+ /**
+ * {@link android.view.ViewGroup.MarginLayoutParams LayoutParams} subclass for children of
+ * {@link RecyclerView}. Custom {@link LayoutManager layout managers} are encouraged
+ * to create their own subclass of this <code>LayoutParams</code> class
+ * to store any additional required per-child view metadata about the layout.
+ */
+ public static class LayoutParams extends android.view.ViewGroup.MarginLayoutParams {
+ ViewHolder mViewHolder;
+ final Rect mDecorInsets = new Rect();
+ boolean mInsetsDirty = true;
+ // Flag is set to true if the view is bound while it is detached from RV.
+ // In this case, we need to manually call invalidate after view is added to guarantee that
+ // invalidation is populated through the View hierarchy
+ boolean mPendingInvalidate = false;
+
+ public LayoutParams(Context c, AttributeSet attrs) {
+ super(c, attrs);
+ }
+
+ public LayoutParams(int width, int height) {
+ super(width, height);
+ }
+
+ public LayoutParams(MarginLayoutParams source) {
+ super(source);
+ }
+
+ public LayoutParams(ViewGroup.LayoutParams source) {
+ super(source);
+ }
+
+ public LayoutParams(LayoutParams source) {
+ super((ViewGroup.LayoutParams) source);
+ }
+
+ /**
+ * Returns true if the view this LayoutParams is attached to needs to have its content
+ * updated from the corresponding adapter.
+ *
+ * @return true if the view should have its content updated
+ */
+ public boolean viewNeedsUpdate() {
+ return mViewHolder.needsUpdate();
+ }
+
+ /**
+ * Returns true if the view this LayoutParams is attached to is now representing
+ * potentially invalid data. A LayoutManager should scrap/recycle it.
+ *
+ * @return true if the view is invalid
+ */
+ public boolean isViewInvalid() {
+ return mViewHolder.isInvalid();
+ }
+
+ /**
+ * Returns true if the adapter data item corresponding to the view this LayoutParams
+ * is attached to has been removed from the data set. A LayoutManager may choose to
+ * treat it differently in order to animate its outgoing or disappearing state.
+ *
+ * @return true if the item the view corresponds to was removed from the data set
+ */
+ public boolean isItemRemoved() {
+ return mViewHolder.isRemoved();
+ }
+
+ /**
+ * Returns true if the adapter data item corresponding to the view this LayoutParams
+ * is attached to has been changed in the data set. A LayoutManager may choose to
+ * treat it differently in order to animate its changing state.
+ *
+ * @return true if the item the view corresponds to was changed in the data set
+ */
+ public boolean isItemChanged() {
+ return mViewHolder.isUpdated();
+ }
+
+ /**
+ * @deprecated use {@link #getViewLayoutPosition()} or {@link #getViewAdapterPosition()}
+ */
+ @Deprecated
+ public int getViewPosition() {
+ return mViewHolder.getPosition();
+ }
+
+ /**
+ * Returns the adapter position that the view this LayoutParams is attached to corresponds
+ * to as of latest layout calculation.
+ *
+ * @return the adapter position this view as of latest layout pass
+ */
+ public int getViewLayoutPosition() {
+ return mViewHolder.getLayoutPosition();
+ }
+
+ /**
+ * Returns the up-to-date adapter position that the view this LayoutParams is attached to
+ * corresponds to.
+ *
+ * @return the up-to-date adapter position this view. It may return
+ * {@link RecyclerView#NO_POSITION} if item represented by this View has been removed or
+ * its up-to-date position cannot be calculated.
+ */
+ public int getViewAdapterPosition() {
+ return mViewHolder.getAdapterPosition();
+ }
+ }
+
+ /**
+ * Observer base class for watching changes to an {@link Adapter}.
+ * See {@link Adapter#registerAdapterDataObserver(AdapterDataObserver)}.
+ */
+ public abstract static class AdapterDataObserver {
+ public void onChanged() {
+ // Do nothing
+ }
+
+ public void onItemRangeChanged(int positionStart, int itemCount) {
+ // do nothing
+ }
+
+ public void onItemRangeChanged(int positionStart, int itemCount, Object payload) {
+ // fallback to onItemRangeChanged(positionStart, itemCount) if app
+ // does not override this method.
+ onItemRangeChanged(positionStart, itemCount);
+ }
+
+ public void onItemRangeInserted(int positionStart, int itemCount) {
+ // do nothing
+ }
+
+ public void onItemRangeRemoved(int positionStart, int itemCount) {
+ // do nothing
+ }
+
+ public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
+ // do nothing
+ }
+ }
+
+ /**
+ * <p>Base class for smooth scrolling. Handles basic tracking of the target view position and
+ * provides methods to trigger a programmatic scroll.</p>
+ *
+ * @see LinearSmoothScroller
+ */
+ public abstract static class SmoothScroller {
+
+ private int mTargetPosition = RecyclerView.NO_POSITION;
+
+ private RecyclerView mRecyclerView;
+
+ private LayoutManager mLayoutManager;
+
+ private boolean mPendingInitialRun;
+
+ private boolean mRunning;
+
+ private View mTargetView;
+
+ private final Action mRecyclingAction;
+
+ public SmoothScroller() {
+ mRecyclingAction = new Action(0, 0);
+ }
+
+ /**
+ * Starts a smooth scroll for the given target position.
+ * <p>In each animation step, {@link RecyclerView} will check
+ * for the target view and call either
+ * {@link #onTargetFound(android.view.View, RecyclerView.State, SmoothScroller.Action)} or
+ * {@link #onSeekTargetStep(int, int, RecyclerView.State, SmoothScroller.Action)} until
+ * SmoothScroller is stopped.</p>
+ *
+ * <p>Note that if RecyclerView finds the target view, it will automatically stop the
+ * SmoothScroller. This <b>does not</b> mean that scroll will stop, it only means it will
+ * stop calling SmoothScroller in each animation step.</p>
+ */
+ void start(RecyclerView recyclerView, LayoutManager layoutManager) {
+ mRecyclerView = recyclerView;
+ mLayoutManager = layoutManager;
+ if (mTargetPosition == RecyclerView.NO_POSITION) {
+ throw new IllegalArgumentException("Invalid target position");
+ }
+ mRecyclerView.mState.mTargetPosition = mTargetPosition;
+ mRunning = true;
+ mPendingInitialRun = true;
+ mTargetView = findViewByPosition(getTargetPosition());
+ onStart();
+ mRecyclerView.mViewFlinger.postOnAnimation();
+ }
+
+ public void setTargetPosition(int targetPosition) {
+ mTargetPosition = targetPosition;
+ }
+
+ /**
+ * @return The LayoutManager to which this SmoothScroller is attached. Will return
+ * <code>null</code> after the SmoothScroller is stopped.
+ */
+ @Nullable
+ public LayoutManager getLayoutManager() {
+ return mLayoutManager;
+ }
+
+ /**
+ * Stops running the SmoothScroller in each animation callback. Note that this does not
+ * cancel any existing {@link Action} updated by
+ * {@link #onTargetFound(android.view.View, RecyclerView.State, SmoothScroller.Action)} or
+ * {@link #onSeekTargetStep(int, int, RecyclerView.State, SmoothScroller.Action)}.
+ */
+ protected final void stop() {
+ if (!mRunning) {
+ return;
+ }
+ onStop();
+ mRecyclerView.mState.mTargetPosition = RecyclerView.NO_POSITION;
+ mTargetView = null;
+ mTargetPosition = RecyclerView.NO_POSITION;
+ mPendingInitialRun = false;
+ mRunning = false;
+ // trigger a cleanup
+ mLayoutManager.onSmoothScrollerStopped(this);
+ // clear references to avoid any potential leak by a custom smooth scroller
+ mLayoutManager = null;
+ mRecyclerView = null;
+ }
+
+ /**
+ * Returns true if SmoothScroller has been started but has not received the first
+ * animation
+ * callback yet.
+ *
+ * @return True if this SmoothScroller is waiting to start
+ */
+ public boolean isPendingInitialRun() {
+ return mPendingInitialRun;
+ }
+
+
+ /**
+ * @return True if SmoothScroller is currently active
+ */
+ public boolean isRunning() {
+ return mRunning;
+ }
+
+ /**
+ * Returns the adapter position of the target item
+ *
+ * @return Adapter position of the target item or
+ * {@link RecyclerView#NO_POSITION} if no target view is set.
+ */
+ public int getTargetPosition() {
+ return mTargetPosition;
+ }
+
+ private void onAnimation(int dx, int dy) {
+ final RecyclerView recyclerView = mRecyclerView;
+ if (!mRunning || mTargetPosition == RecyclerView.NO_POSITION || recyclerView == null) {
+ stop();
+ }
+ mPendingInitialRun = false;
+ if (mTargetView != null) {
+ // verify target position
+ if (getChildPosition(mTargetView) == mTargetPosition) {
+ onTargetFound(mTargetView, recyclerView.mState, mRecyclingAction);
+ mRecyclingAction.runIfNecessary(recyclerView);
+ stop();
+ } else {
+ Log.e(TAG, "Passed over target position while smooth scrolling.");
+ mTargetView = null;
+ }
+ }
+ if (mRunning) {
+ onSeekTargetStep(dx, dy, recyclerView.mState, mRecyclingAction);
+ boolean hadJumpTarget = mRecyclingAction.hasJumpTarget();
+ mRecyclingAction.runIfNecessary(recyclerView);
+ if (hadJumpTarget) {
+ // It is not stopped so needs to be restarted
+ if (mRunning) {
+ mPendingInitialRun = true;
+ recyclerView.mViewFlinger.postOnAnimation();
+ } else {
+ stop(); // done
+ }
+ }
+ }
+ }
+
+ /**
+ * @see RecyclerView#getChildLayoutPosition(android.view.View)
+ */
+ public int getChildPosition(View view) {
+ return mRecyclerView.getChildLayoutPosition(view);
+ }
+
+ /**
+ * @see RecyclerView.LayoutManager#getChildCount()
+ */
+ public int getChildCount() {
+ return mRecyclerView.mLayout.getChildCount();
+ }
+
+ /**
+ * @see RecyclerView.LayoutManager#findViewByPosition(int)
+ */
+ public View findViewByPosition(int position) {
+ return mRecyclerView.mLayout.findViewByPosition(position);
+ }
+
+ /**
+ * @see RecyclerView#scrollToPosition(int)
+ * @deprecated Use {@link Action#jumpTo(int)}.
+ */
+ @Deprecated
+ public void instantScrollToPosition(int position) {
+ mRecyclerView.scrollToPosition(position);
+ }
+
+ protected void onChildAttachedToWindow(View child) {
+ if (getChildPosition(child) == getTargetPosition()) {
+ mTargetView = child;
+ if (DEBUG) {
+ Log.d(TAG, "smooth scroll target view has been attached");
+ }
+ }
+ }
+
+ /**
+ * Normalizes the vector.
+ * @param scrollVector The vector that points to the target scroll position
+ */
+ protected void normalize(PointF scrollVector) {
+ final double magnitude = Math.sqrt(scrollVector.x * scrollVector.x + scrollVector.y
+ * scrollVector.y);
+ scrollVector.x /= magnitude;
+ scrollVector.y /= magnitude;
+ }
+
+ /**
+ * Called when smooth scroll is started. This might be a good time to do setup.
+ */
+ protected abstract void onStart();
+
+ /**
+ * Called when smooth scroller is stopped. This is a good place to cleanup your state etc.
+ * @see #stop()
+ */
+ protected abstract void onStop();
+
+ /**
+ * <p>RecyclerView will call this method each time it scrolls until it can find the target
+ * position in the layout.</p>
+ * <p>SmoothScroller should check dx, dy and if scroll should be changed, update the
+ * provided {@link Action} to define the next scroll.</p>
+ *
+ * @param dx Last scroll amount horizontally
+ * @param dy Last scroll amount vertically
+ * @param state Transient state of RecyclerView
+ * @param action If you want to trigger a new smooth scroll and cancel the previous one,
+ * update this object.
+ */
+ protected abstract void onSeekTargetStep(int dx, int dy, State state, Action action);
+
+ /**
+ * Called when the target position is laid out. This is the last callback SmoothScroller
+ * will receive and it should update the provided {@link Action} to define the scroll
+ * details towards the target view.
+ * @param targetView The view element which render the target position.
+ * @param state Transient state of RecyclerView
+ * @param action Action instance that you should update to define final scroll action
+ * towards the targetView
+ */
+ protected abstract void onTargetFound(View targetView, State state, Action action);
+
+ /**
+ * Holds information about a smooth scroll request by a {@link SmoothScroller}.
+ */
+ public static class Action {
+
+ public static final int UNDEFINED_DURATION = Integer.MIN_VALUE;
+
+ private int mDx;
+
+ private int mDy;
+
+ private int mDuration;
+
+ private int mJumpToPosition = NO_POSITION;
+
+ private Interpolator mInterpolator;
+
+ private boolean mChanged = false;
+
+ // we track this variable to inform custom implementer if they are updating the action
+ // in every animation callback
+ private int mConsecutiveUpdates = 0;
+
+ /**
+ * @param dx Pixels to scroll horizontally
+ * @param dy Pixels to scroll vertically
+ */
+ public Action(int dx, int dy) {
+ this(dx, dy, UNDEFINED_DURATION, null);
+ }
+
+ /**
+ * @param dx Pixels to scroll horizontally
+ * @param dy Pixels to scroll vertically
+ * @param duration Duration of the animation in milliseconds
+ */
+ public Action(int dx, int dy, int duration) {
+ this(dx, dy, duration, null);
+ }
+
+ /**
+ * @param dx Pixels to scroll horizontally
+ * @param dy Pixels to scroll vertically
+ * @param duration Duration of the animation in milliseconds
+ * @param interpolator Interpolator to be used when calculating scroll position in each
+ * animation step
+ */
+ public Action(int dx, int dy, int duration, Interpolator interpolator) {
+ mDx = dx;
+ mDy = dy;
+ mDuration = duration;
+ mInterpolator = interpolator;
+ }
+
+ /**
+ * Instead of specifying pixels to scroll, use the target position to jump using
+ * {@link RecyclerView#scrollToPosition(int)}.
+ * <p>
+ * You may prefer using this method if scroll target is really far away and you prefer
+ * to jump to a location and smooth scroll afterwards.
+ * <p>
+ * Note that calling this method takes priority over other update methods such as
+ * {@link #update(int, int, int, Interpolator)}, {@link #setX(float)},
+ * {@link #setY(float)} and #{@link #setInterpolator(Interpolator)}. If you call
+ * {@link #jumpTo(int)}, the other changes will not be considered for this animation
+ * frame.
+ *
+ * @param targetPosition The target item position to scroll to using instant scrolling.
+ */
+ public void jumpTo(int targetPosition) {
+ mJumpToPosition = targetPosition;
+ }
+
+ boolean hasJumpTarget() {
+ return mJumpToPosition >= 0;
+ }
+
+ void runIfNecessary(RecyclerView recyclerView) {
+ if (mJumpToPosition >= 0) {
+ final int position = mJumpToPosition;
+ mJumpToPosition = NO_POSITION;
+ recyclerView.jumpToPositionForSmoothScroller(position);
+ mChanged = false;
+ return;
+ }
+ if (mChanged) {
+ validate();
+ if (mInterpolator == null) {
+ if (mDuration == UNDEFINED_DURATION) {
+ recyclerView.mViewFlinger.smoothScrollBy(mDx, mDy);
+ } else {
+ recyclerView.mViewFlinger.smoothScrollBy(mDx, mDy, mDuration);
+ }
+ } else {
+ recyclerView.mViewFlinger.smoothScrollBy(
+ mDx, mDy, mDuration, mInterpolator);
+ }
+ mConsecutiveUpdates++;
+ if (mConsecutiveUpdates > 10) {
+ // A new action is being set in every animation step. This looks like a bad
+ // implementation. Inform developer.
+ Log.e(TAG, "Smooth Scroll action is being updated too frequently. Make sure"
+ + " you are not changing it unless necessary");
+ }
+ mChanged = false;
+ } else {
+ mConsecutiveUpdates = 0;
+ }
+ }
+
+ private void validate() {
+ if (mInterpolator != null && mDuration < 1) {
+ throw new IllegalStateException("If you provide an interpolator, you must"
+ + " set a positive duration");
+ } else if (mDuration < 1) {
+ throw new IllegalStateException("Scroll duration must be a positive number");
+ }
+ }
+
+ public int getDx() {
+ return mDx;
+ }
+
+ public void setDx(int dx) {
+ mChanged = true;
+ mDx = dx;
+ }
+
+ public int getDy() {
+ return mDy;
+ }
+
+ public void setDy(int dy) {
+ mChanged = true;
+ mDy = dy;
+ }
+
+ public int getDuration() {
+ return mDuration;
+ }
+
+ public void setDuration(int duration) {
+ mChanged = true;
+ mDuration = duration;
+ }
+
+ public Interpolator getInterpolator() {
+ return mInterpolator;
+ }
+
+ /**
+ * Sets the interpolator to calculate scroll steps
+ * @param interpolator The interpolator to use. If you specify an interpolator, you must
+ * also set the duration.
+ * @see #setDuration(int)
+ */
+ public void setInterpolator(Interpolator interpolator) {
+ mChanged = true;
+ mInterpolator = interpolator;
+ }
+
+ /**
+ * Updates the action with given parameters.
+ * @param dx Pixels to scroll horizontally
+ * @param dy Pixels to scroll vertically
+ * @param duration Duration of the animation in milliseconds
+ * @param interpolator Interpolator to be used when calculating scroll position in each
+ * animation step
+ */
+ public void update(int dx, int dy, int duration, Interpolator interpolator) {
+ mDx = dx;
+ mDy = dy;
+ mDuration = duration;
+ mInterpolator = interpolator;
+ mChanged = true;
+ }
+ }
+
+ /**
+ * An interface which is optionally implemented by custom {@link RecyclerView.LayoutManager}
+ * to provide a hint to a {@link SmoothScroller} about the location of the target position.
+ */
+ public interface ScrollVectorProvider {
+ /**
+ * Should calculate the vector that points to the direction where the target position
+ * can be found.
+ * <p>
+ * This method is used by the {@link LinearSmoothScroller} to initiate a scroll towards
+ * the target position.
+ * <p>
+ * The magnitude of the vector is not important. It is always normalized before being
+ * used by the {@link LinearSmoothScroller}.
+ * <p>
+ * LayoutManager should not check whether the position exists in the adapter or not.
+ *
+ * @param targetPosition the target position to which the returned vector should point
+ *
+ * @return the scroll vector for a given position.
+ */
+ PointF computeScrollVectorForPosition(int targetPosition);
+ }
+ }
+
+ static class AdapterDataObservable extends Observable<AdapterDataObserver> {
+ public boolean hasObservers() {
+ return !mObservers.isEmpty();
+ }
+
+ public void notifyChanged() {
+ // since onChanged() is implemented by the app, it could do anything, including
+ // removing itself from {@link mObservers} - and that could cause problems if
+ // an iterator is used on the ArrayList {@link mObservers}.
+ // to avoid such problems, just march thru the list in the reverse order.
+ for (int i = mObservers.size() - 1; i >= 0; i--) {
+ mObservers.get(i).onChanged();
+ }
+ }
+
+ public void notifyItemRangeChanged(int positionStart, int itemCount) {
+ notifyItemRangeChanged(positionStart, itemCount, null);
+ }
+
+ public void notifyItemRangeChanged(int positionStart, int itemCount, Object payload) {
+ // since onItemRangeChanged() is implemented by the app, it could do anything, including
+ // removing itself from {@link mObservers} - and that could cause problems if
+ // an iterator is used on the ArrayList {@link mObservers}.
+ // to avoid such problems, just march thru the list in the reverse order.
+ for (int i = mObservers.size() - 1; i >= 0; i--) {
+ mObservers.get(i).onItemRangeChanged(positionStart, itemCount, payload);
+ }
+ }
+
+ public void notifyItemRangeInserted(int positionStart, int itemCount) {
+ // since onItemRangeInserted() is implemented by the app, it could do anything,
+ // including removing itself from {@link mObservers} - and that could cause problems if
+ // an iterator is used on the ArrayList {@link mObservers}.
+ // to avoid such problems, just march thru the list in the reverse order.
+ for (int i = mObservers.size() - 1; i >= 0; i--) {
+ mObservers.get(i).onItemRangeInserted(positionStart, itemCount);
+ }
+ }
+
+ public void notifyItemRangeRemoved(int positionStart, int itemCount) {
+ // since onItemRangeRemoved() is implemented by the app, it could do anything, including
+ // removing itself from {@link mObservers} - and that could cause problems if
+ // an iterator is used on the ArrayList {@link mObservers}.
+ // to avoid such problems, just march thru the list in the reverse order.
+ for (int i = mObservers.size() - 1; i >= 0; i--) {
+ mObservers.get(i).onItemRangeRemoved(positionStart, itemCount);
+ }
+ }
+
+ public void notifyItemMoved(int fromPosition, int toPosition) {
+ for (int i = mObservers.size() - 1; i >= 0; i--) {
+ mObservers.get(i).onItemRangeMoved(fromPosition, toPosition, 1);
+ }
+ }
+ }
+
+ /**
+ * This is public so that the CREATOR can be access on cold launch.
+ * @hide
+ */
+ public static class SavedState extends AbsSavedState {
+
+ Parcelable mLayoutState;
+
+ /**
+ * called by CREATOR
+ */
+ SavedState(Parcel in) {
+ super(in);
+ mLayoutState = in.readParcelable(LayoutManager.class.getClassLoader());
+ }
+
+ /**
+ * Called by onSaveInstanceState
+ */
+ SavedState(Parcelable superState) {
+ super(superState);
+ }
+
+ @Override
+ public void writeToParcel(Parcel dest, int flags) {
+ super.writeToParcel(dest, flags);
+ dest.writeParcelable(mLayoutState, 0);
+ }
+
+ void copyFrom(SavedState other) {
+ mLayoutState = other.mLayoutState;
+ }
+
+ public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
+ @Override
+ public SavedState createFromParcel(Parcel in) {
+ return new SavedState(in);
+ }
+
+ @Override
+ public SavedState[] newArray(int size) {
+ return new SavedState[size];
+ }
+ };
+ }
+ /**
+ * <p>Contains useful information about the current RecyclerView state like target scroll
+ * position or view focus. State object can also keep arbitrary data, identified by resource
+ * ids.</p>
+ * <p>Often times, RecyclerView components will need to pass information between each other.
+ * To provide a well defined data bus between components, RecyclerView passes the same State
+ * object to component callbacks and these components can use it to exchange data.</p>
+ * <p>If you implement custom components, you can use State's put/get/remove methods to pass
+ * data between your components without needing to manage their lifecycles.</p>
+ */
+ public static class State {
+ static final int STEP_START = 1;
+ static final int STEP_LAYOUT = 1 << 1;
+ static final int STEP_ANIMATIONS = 1 << 2;
+
+ void assertLayoutStep(int accepted) {
+ if ((accepted & mLayoutStep) == 0) {
+ throw new IllegalStateException("Layout state should be one of "
+ + Integer.toBinaryString(accepted) + " but it is "
+ + Integer.toBinaryString(mLayoutStep));
+ }
+ }
+
+
+ /** Owned by SmoothScroller */
+ private int mTargetPosition = RecyclerView.NO_POSITION;
+
+ private SparseArray<Object> mData;
+
+ ////////////////////////////////////////////////////////////////////////////////////////////
+ // Fields below are carried from one layout pass to the next
+ ////////////////////////////////////////////////////////////////////////////////////////////
+
+ /**
+ * Number of items adapter had in the previous layout.
+ */
+ int mPreviousLayoutItemCount = 0;
+
+ /**
+ * Number of items that were NOT laid out but has been deleted from the adapter after the
+ * previous layout.
+ */
+ int mDeletedInvisibleItemCountSincePreviousLayout = 0;
+
+ ////////////////////////////////////////////////////////////////////////////////////////////
+ // Fields below must be updated or cleared before they are used (generally before a pass)
+ ////////////////////////////////////////////////////////////////////////////////////////////
+
+ @IntDef(flag = true, value = {
+ STEP_START, STEP_LAYOUT, STEP_ANIMATIONS
+ })
+ @Retention(RetentionPolicy.SOURCE)
+ @interface LayoutState {}
+
+ @LayoutState
+ int mLayoutStep = STEP_START;
+
+ /**
+ * Number of items adapter has.
+ */
+ int mItemCount = 0;
+
+ boolean mStructureChanged = false;
+
+ boolean mInPreLayout = false;
+
+ boolean mTrackOldChangeHolders = false;
+
+ boolean mIsMeasuring = false;
+
+ ////////////////////////////////////////////////////////////////////////////////////////////
+ // Fields below are always reset outside of the pass (or passes) that use them
+ ////////////////////////////////////////////////////////////////////////////////////////////
+
+ boolean mRunSimpleAnimations = false;
+
+ boolean mRunPredictiveAnimations = false;
+
+ /**
+ * This data is saved before a layout calculation happens. After the layout is finished,
+ * if the previously focused view has been replaced with another view for the same item, we
+ * move the focus to the new item automatically.
+ */
+ int mFocusedItemPosition;
+ long mFocusedItemId;
+ // when a sub child has focus, record its id and see if we can directly request focus on
+ // that one instead
+ int mFocusedSubChildId;
+
+ ////////////////////////////////////////////////////////////////////////////////////////////
+
+ State reset() {
+ mTargetPosition = RecyclerView.NO_POSITION;
+ if (mData != null) {
+ mData.clear();
+ }
+ mItemCount = 0;
+ mStructureChanged = false;
+ mIsMeasuring = false;
+ return this;
+ }
+
+ /**
+ * Prepare for a prefetch occurring on the RecyclerView in between traversals, potentially
+ * prior to any layout passes.
+ *
+ * <p>Don't touch any state stored between layout passes, only reset per-layout state, so
+ * that Recycler#getViewForPosition() can function safely.</p>
+ */
+ void prepareForNestedPrefetch(Adapter adapter) {
+ mLayoutStep = STEP_START;
+ mItemCount = adapter.getItemCount();
+ mStructureChanged = false;
+ mInPreLayout = false;
+ mTrackOldChangeHolders = false;
+ mIsMeasuring = false;
+ }
+
+ /**
+ * Returns true if the RecyclerView is currently measuring the layout. This value is
+ * {@code true} only if the LayoutManager opted into the auto measure API and RecyclerView
+ * has non-exact measurement specs.
+ * <p>
+ * Note that if the LayoutManager supports predictive animations and it is calculating the
+ * pre-layout step, this value will be {@code false} even if the RecyclerView is in
+ * {@code onMeasure} call. This is because pre-layout means the previous state of the
+ * RecyclerView and measurements made for that state cannot change the RecyclerView's size.
+ * LayoutManager is always guaranteed to receive another call to
+ * {@link LayoutManager#onLayoutChildren(Recycler, State)} when this happens.
+ *
+ * @return True if the RecyclerView is currently calculating its bounds, false otherwise.
+ */
+ public boolean isMeasuring() {
+ return mIsMeasuring;
+ }
+
+ /**
+ * Returns true if
+ * @return
+ */
+ public boolean isPreLayout() {
+ return mInPreLayout;
+ }
+
+ /**
+ * Returns whether RecyclerView will run predictive animations in this layout pass
+ * or not.
+ *
+ * @return true if RecyclerView is calculating predictive animations to be run at the end
+ * of the layout pass.
+ */
+ public boolean willRunPredictiveAnimations() {
+ return mRunPredictiveAnimations;
+ }
+
+ /**
+ * Returns whether RecyclerView will run simple animations in this layout pass
+ * or not.
+ *
+ * @return true if RecyclerView is calculating simple animations to be run at the end of
+ * the layout pass.
+ */
+ public boolean willRunSimpleAnimations() {
+ return mRunSimpleAnimations;
+ }
+
+ /**
+ * Removes the mapping from the specified id, if there was any.
+ * @param resourceId Id of the resource you want to remove. It is suggested to use R.id.* to
+ * preserve cross functionality and avoid conflicts.
+ */
+ public void remove(int resourceId) {
+ if (mData == null) {
+ return;
+ }
+ mData.remove(resourceId);
+ }
+
+ /**
+ * Gets the Object mapped from the specified id, or <code>null</code>
+ * if no such data exists.
+ *
+ * @param resourceId Id of the resource you want to remove. It is suggested to use R.id.*
+ * to
+ * preserve cross functionality and avoid conflicts.
+ */
+ public <T> T get(int resourceId) {
+ if (mData == null) {
+ return null;
+ }
+ return (T) mData.get(resourceId);
+ }
+
+ /**
+ * Adds a mapping from the specified id to the specified value, replacing the previous
+ * mapping from the specified key if there was one.
+ *
+ * @param resourceId Id of the resource you want to add. It is suggested to use R.id.* to
+ * preserve cross functionality and avoid conflicts.
+ * @param data The data you want to associate with the resourceId.
+ */
+ public void put(int resourceId, Object data) {
+ if (mData == null) {
+ mData = new SparseArray<Object>();
+ }
+ mData.put(resourceId, data);
+ }
+
+ /**
+ * If scroll is triggered to make a certain item visible, this value will return the
+ * adapter index of that item.
+ * @return Adapter index of the target item or
+ * {@link RecyclerView#NO_POSITION} if there is no target
+ * position.
+ */
+ public int getTargetScrollPosition() {
+ return mTargetPosition;
+ }
+
+ /**
+ * Returns if current scroll has a target position.
+ * @return true if scroll is being triggered to make a certain position visible
+ * @see #getTargetScrollPosition()
+ */
+ public boolean hasTargetScrollPosition() {
+ return mTargetPosition != RecyclerView.NO_POSITION;
+ }
+
+ /**
+ * @return true if the structure of the data set has changed since the last call to
+ * onLayoutChildren, false otherwise
+ */
+ public boolean didStructureChange() {
+ return mStructureChanged;
+ }
+
+ /**
+ * Returns the total number of items that can be laid out. Note that this number is not
+ * necessarily equal to the number of items in the adapter, so you should always use this
+ * number for your position calculations and never access the adapter directly.
+ * <p>
+ * RecyclerView listens for Adapter's notify events and calculates the effects of adapter
+ * data changes on existing Views. These calculations are used to decide which animations
+ * should be run.
+ * <p>
+ * To support predictive animations, RecyclerView may rewrite or reorder Adapter changes to
+ * present the correct state to LayoutManager in pre-layout pass.
+ * <p>
+ * For example, a newly added item is not included in pre-layout item count because
+ * pre-layout reflects the contents of the adapter before the item is added. Behind the
+ * scenes, RecyclerView offsets {@link Recycler#getViewForPosition(int)} calls such that
+ * LayoutManager does not know about the new item's existence in pre-layout. The item will
+ * be available in second layout pass and will be included in the item count. Similar
+ * adjustments are made for moved and removed items as well.
+ * <p>
+ * You can get the adapter's item count via {@link LayoutManager#getItemCount()} method.
+ *
+ * @return The number of items currently available
+ * @see LayoutManager#getItemCount()
+ */
+ public int getItemCount() {
+ return mInPreLayout
+ ? (mPreviousLayoutItemCount - mDeletedInvisibleItemCountSincePreviousLayout)
+ : mItemCount;
+ }
+
+ @Override
+ public String toString() {
+ return "State{"
+ + "mTargetPosition=" + mTargetPosition
+ + ", mData=" + mData
+ + ", mItemCount=" + mItemCount
+ + ", mPreviousLayoutItemCount=" + mPreviousLayoutItemCount
+ + ", mDeletedInvisibleItemCountSincePreviousLayout="
+ + mDeletedInvisibleItemCountSincePreviousLayout
+ + ", mStructureChanged=" + mStructureChanged
+ + ", mInPreLayout=" + mInPreLayout
+ + ", mRunSimpleAnimations=" + mRunSimpleAnimations
+ + ", mRunPredictiveAnimations=" + mRunPredictiveAnimations
+ + '}';
+ }
+ }
+
+ /**
+ * This class defines the behavior of fling if the developer wishes to handle it.
+ * <p>
+ * Subclasses of {@link OnFlingListener} can be used to implement custom fling behavior.
+ *
+ * @see #setOnFlingListener(OnFlingListener)
+ */
+ public abstract static class OnFlingListener {
+
+ /**
+ * Override this to handle a fling given the velocities in both x and y directions.
+ * Note that this method will only be called if the associated {@link LayoutManager}
+ * supports scrolling and the fling is not handled by nested scrolls first.
+ *
+ * @param velocityX the fling velocity on the X axis
+ * @param velocityY the fling velocity on the Y axis
+ *
+ * @return true if the fling washandled, false otherwise.
+ */
+ public abstract boolean onFling(int velocityX, int velocityY);
+ }
+
+ /**
+ * Internal listener that manages items after animations finish. This is how items are
+ * retained (not recycled) during animations, but allowed to be recycled afterwards.
+ * It depends on the contract with the ItemAnimator to call the appropriate dispatch*Finished()
+ * method on the animator's listener when it is done animating any item.
+ */
+ private class ItemAnimatorRestoreListener implements ItemAnimator.ItemAnimatorListener {
+
+ ItemAnimatorRestoreListener() {
+ }
+
+ @Override
+ public void onAnimationFinished(ViewHolder item) {
+ item.setIsRecyclable(true);
+ if (item.mShadowedHolder != null && item.mShadowingHolder == null) { // old vh
+ item.mShadowedHolder = null;
+ }
+ // always null this because an OldViewHolder can never become NewViewHolder w/o being
+ // recycled.
+ item.mShadowingHolder = null;
+ if (!item.shouldBeKeptAsChild()) {
+ if (!removeAnimatingView(item.itemView) && item.isTmpDetached()) {
+ removeDetachedView(item.itemView, false);
+ }
+ }
+ }
+ }
+
+ /**
+ * This class defines the animations that take place on items as changes are made
+ * to the adapter.
+ *
+ * Subclasses of ItemAnimator can be used to implement custom animations for actions on
+ * ViewHolder items. The RecyclerView will manage retaining these items while they
+ * are being animated, but implementors must call {@link #dispatchAnimationFinished(ViewHolder)}
+ * when a ViewHolder's animation is finished. In other words, there must be a matching
+ * {@link #dispatchAnimationFinished(ViewHolder)} call for each
+ * {@link #animateAppearance(ViewHolder, ItemHolderInfo, ItemHolderInfo) animateAppearance()},
+ * {@link #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateChange()}
+ * {@link #animatePersistence(ViewHolder, ItemHolderInfo, ItemHolderInfo) animatePersistence()},
+ * and
+ * {@link #animateDisappearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateDisappearance()} call.
+ *
+ * <p>By default, RecyclerView uses {@link DefaultItemAnimator}.</p>
+ *
+ * @see #setItemAnimator(ItemAnimator)
+ */
+ @SuppressWarnings("UnusedParameters")
+ public abstract static class ItemAnimator {
+
+ /**
+ * The Item represented by this ViewHolder is updated.
+ * <p>
+ * @see #recordPreLayoutInformation(State, ViewHolder, int, List)
+ */
+ public static final int FLAG_CHANGED = ViewHolder.FLAG_UPDATE;
+
+ /**
+ * The Item represented by this ViewHolder is removed from the adapter.
+ * <p>
+ * @see #recordPreLayoutInformation(State, ViewHolder, int, List)
+ */
+ public static final int FLAG_REMOVED = ViewHolder.FLAG_REMOVED;
+
+ /**
+ * Adapter {@link Adapter#notifyDataSetChanged()} has been called and the content
+ * represented by this ViewHolder is invalid.
+ * <p>
+ * @see #recordPreLayoutInformation(State, ViewHolder, int, List)
+ */
+ public static final int FLAG_INVALIDATED = ViewHolder.FLAG_INVALID;
+
+ /**
+ * The position of the Item represented by this ViewHolder has been changed. This flag is
+ * not bound to {@link Adapter#notifyItemMoved(int, int)}. It might be set in response to
+ * any adapter change that may have a side effect on this item. (e.g. The item before this
+ * one has been removed from the Adapter).
+ * <p>
+ * @see #recordPreLayoutInformation(State, ViewHolder, int, List)
+ */
+ public static final int FLAG_MOVED = ViewHolder.FLAG_MOVED;
+
+ /**
+ * This ViewHolder was not laid out but has been added to the layout in pre-layout state
+ * by the {@link LayoutManager}. This means that the item was already in the Adapter but
+ * invisible and it may become visible in the post layout phase. LayoutManagers may prefer
+ * to add new items in pre-layout to specify their virtual location when they are invisible
+ * (e.g. to specify the item should <i>animate in</i> from below the visible area).
+ * <p>
+ * @see #recordPreLayoutInformation(State, ViewHolder, int, List)
+ */
+ public static final int FLAG_APPEARED_IN_PRE_LAYOUT =
+ ViewHolder.FLAG_APPEARED_IN_PRE_LAYOUT;
+
+ /**
+ * The set of flags that might be passed to
+ * {@link #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ */
+ @IntDef(flag = true, value = {
+ FLAG_CHANGED, FLAG_REMOVED, FLAG_MOVED, FLAG_INVALIDATED,
+ FLAG_APPEARED_IN_PRE_LAYOUT
+ })
+ @Retention(RetentionPolicy.SOURCE)
+ public @interface AdapterChanges {}
+ private ItemAnimatorListener mListener = null;
+ private ArrayList<ItemAnimatorFinishedListener> mFinishedListeners =
+ new ArrayList<ItemAnimatorFinishedListener>();
+
+ private long mAddDuration = 120;
+ private long mRemoveDuration = 120;
+ private long mMoveDuration = 250;
+ private long mChangeDuration = 250;
+
+ /**
+ * Gets the current duration for which all move animations will run.
+ *
+ * @return The current move duration
+ */
+ public long getMoveDuration() {
+ return mMoveDuration;
+ }
+
+ /**
+ * Sets the duration for which all move animations will run.
+ *
+ * @param moveDuration The move duration
+ */
+ public void setMoveDuration(long moveDuration) {
+ mMoveDuration = moveDuration;
+ }
+
+ /**
+ * Gets the current duration for which all add animations will run.
+ *
+ * @return The current add duration
+ */
+ public long getAddDuration() {
+ return mAddDuration;
+ }
+
+ /**
+ * Sets the duration for which all add animations will run.
+ *
+ * @param addDuration The add duration
+ */
+ public void setAddDuration(long addDuration) {
+ mAddDuration = addDuration;
+ }
+
+ /**
+ * Gets the current duration for which all remove animations will run.
+ *
+ * @return The current remove duration
+ */
+ public long getRemoveDuration() {
+ return mRemoveDuration;
+ }
+
+ /**
+ * Sets the duration for which all remove animations will run.
+ *
+ * @param removeDuration The remove duration
+ */
+ public void setRemoveDuration(long removeDuration) {
+ mRemoveDuration = removeDuration;
+ }
+
+ /**
+ * Gets the current duration for which all change animations will run.
+ *
+ * @return The current change duration
+ */
+ public long getChangeDuration() {
+ return mChangeDuration;
+ }
+
+ /**
+ * Sets the duration for which all change animations will run.
+ *
+ * @param changeDuration The change duration
+ */
+ public void setChangeDuration(long changeDuration) {
+ mChangeDuration = changeDuration;
+ }
+
+ /**
+ * Internal only:
+ * Sets the listener that must be called when the animator is finished
+ * animating the item (or immediately if no animation happens). This is set
+ * internally and is not intended to be set by external code.
+ *
+ * @param listener The listener that must be called.
+ */
+ void setListener(ItemAnimatorListener listener) {
+ mListener = listener;
+ }
+
+ /**
+ * Called by the RecyclerView before the layout begins. Item animator should record
+ * necessary information about the View before it is potentially rebound, moved or removed.
+ * <p>
+ * The data returned from this method will be passed to the related <code>animate**</code>
+ * methods.
+ * <p>
+ * Note that this method may be called after pre-layout phase if LayoutManager adds new
+ * Views to the layout in pre-layout pass.
+ * <p>
+ * The default implementation returns an {@link ItemHolderInfo} which holds the bounds of
+ * the View and the adapter change flags.
+ *
+ * @param state The current State of RecyclerView which includes some useful data
+ * about the layout that will be calculated.
+ * @param viewHolder The ViewHolder whose information should be recorded.
+ * @param changeFlags Additional information about what changes happened in the Adapter
+ * about the Item represented by this ViewHolder. For instance, if
+ * item is deleted from the adapter, {@link #FLAG_REMOVED} will be set.
+ * @param payloads The payload list that was previously passed to
+ * {@link Adapter#notifyItemChanged(int, Object)} or
+ * {@link Adapter#notifyItemRangeChanged(int, int, Object)}.
+ *
+ * @return An ItemHolderInfo instance that preserves necessary information about the
+ * ViewHolder. This object will be passed back to related <code>animate**</code> methods
+ * after layout is complete.
+ *
+ * @see #recordPostLayoutInformation(State, ViewHolder)
+ * @see #animateAppearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * @see #animateDisappearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * @see #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * @see #animatePersistence(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ */
+ public @NonNull ItemHolderInfo recordPreLayoutInformation(@NonNull State state,
+ @NonNull ViewHolder viewHolder, @AdapterChanges int changeFlags,
+ @NonNull List<Object> payloads) {
+ return obtainHolderInfo().setFrom(viewHolder);
+ }
+
+ /**
+ * Called by the RecyclerView after the layout is complete. Item animator should record
+ * necessary information about the View's final state.
+ * <p>
+ * The data returned from this method will be passed to the related <code>animate**</code>
+ * methods.
+ * <p>
+ * The default implementation returns an {@link ItemHolderInfo} which holds the bounds of
+ * the View.
+ *
+ * @param state The current State of RecyclerView which includes some useful data about
+ * the layout that will be calculated.
+ * @param viewHolder The ViewHolder whose information should be recorded.
+ *
+ * @return An ItemHolderInfo that preserves necessary information about the ViewHolder.
+ * This object will be passed back to related <code>animate**</code> methods when
+ * RecyclerView decides how items should be animated.
+ *
+ * @see #recordPreLayoutInformation(State, ViewHolder, int, List)
+ * @see #animateAppearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * @see #animateDisappearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * @see #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * @see #animatePersistence(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ */
+ public @NonNull ItemHolderInfo recordPostLayoutInformation(@NonNull State state,
+ @NonNull ViewHolder viewHolder) {
+ return obtainHolderInfo().setFrom(viewHolder);
+ }
+
+ /**
+ * Called by the RecyclerView when a ViewHolder has disappeared from the layout.
+ * <p>
+ * This means that the View was a child of the LayoutManager when layout started but has
+ * been removed by the LayoutManager. It might have been removed from the adapter or simply
+ * become invisible due to other factors. You can distinguish these two cases by checking
+ * the change flags that were passed to
+ * {@link #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ * <p>
+ * Note that when a ViewHolder both changes and disappears in the same layout pass, the
+ * animation callback method which will be called by the RecyclerView depends on the
+ * ItemAnimator's decision whether to re-use the same ViewHolder or not, and also the
+ * LayoutManager's decision whether to layout the changed version of a disappearing
+ * ViewHolder or not. RecyclerView will call
+ * {@link #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateChange} instead of {@code animateDisappearance} if and only if the ItemAnimator
+ * returns {@code false} from
+ * {@link #canReuseUpdatedViewHolder(ViewHolder) canReuseUpdatedViewHolder} and the
+ * LayoutManager lays out a new disappearing view that holds the updated information.
+ * Built-in LayoutManagers try to avoid laying out updated versions of disappearing views.
+ * <p>
+ * If LayoutManager supports predictive animations, it might provide a target disappear
+ * location for the View by laying it out in that location. When that happens,
+ * RecyclerView will call {@link #recordPostLayoutInformation(State, ViewHolder)} and the
+ * response of that call will be passed to this method as the <code>postLayoutInfo</code>.
+ * <p>
+ * ItemAnimator must call {@link #dispatchAnimationFinished(ViewHolder)} when the animation
+ * is complete (or instantly call {@link #dispatchAnimationFinished(ViewHolder)} if it
+ * decides not to animate the view).
+ *
+ * @param viewHolder The ViewHolder which should be animated
+ * @param preLayoutInfo The information that was returned from
+ * {@link #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ * @param postLayoutInfo The information that was returned from
+ * {@link #recordPostLayoutInformation(State, ViewHolder)}. Might be
+ * null if the LayoutManager did not layout the item.
+ *
+ * @return true if a later call to {@link #runPendingAnimations()} is requested,
+ * false otherwise.
+ */
+ public abstract boolean animateDisappearance(@NonNull ViewHolder viewHolder,
+ @NonNull ItemHolderInfo preLayoutInfo, @Nullable ItemHolderInfo postLayoutInfo);
+
+ /**
+ * Called by the RecyclerView when a ViewHolder is added to the layout.
+ * <p>
+ * In detail, this means that the ViewHolder was <b>not</b> a child when the layout started
+ * but has been added by the LayoutManager. It might be newly added to the adapter or
+ * simply become visible due to other factors.
+ * <p>
+ * ItemAnimator must call {@link #dispatchAnimationFinished(ViewHolder)} when the animation
+ * is complete (or instantly call {@link #dispatchAnimationFinished(ViewHolder)} if it
+ * decides not to animate the view).
+ *
+ * @param viewHolder The ViewHolder which should be animated
+ * @param preLayoutInfo The information that was returned from
+ * {@link #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ * Might be null if Item was just added to the adapter or
+ * LayoutManager does not support predictive animations or it could
+ * not predict that this ViewHolder will become visible.
+ * @param postLayoutInfo The information that was returned from {@link
+ * #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ *
+ * @return true if a later call to {@link #runPendingAnimations()} is requested,
+ * false otherwise.
+ */
+ public abstract boolean animateAppearance(@NonNull ViewHolder viewHolder,
+ @Nullable ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo);
+
+ /**
+ * Called by the RecyclerView when a ViewHolder is present in both before and after the
+ * layout and RecyclerView has not received a {@link Adapter#notifyItemChanged(int)} call
+ * for it or a {@link Adapter#notifyDataSetChanged()} call.
+ * <p>
+ * This ViewHolder still represents the same data that it was representing when the layout
+ * started but its position / size may be changed by the LayoutManager.
+ * <p>
+ * If the Item's layout position didn't change, RecyclerView still calls this method because
+ * it does not track this information (or does not necessarily know that an animation is
+ * not required). Your ItemAnimator should handle this case and if there is nothing to
+ * animate, it should call {@link #dispatchAnimationFinished(ViewHolder)} and return
+ * <code>false</code>.
+ * <p>
+ * ItemAnimator must call {@link #dispatchAnimationFinished(ViewHolder)} when the animation
+ * is complete (or instantly call {@link #dispatchAnimationFinished(ViewHolder)} if it
+ * decides not to animate the view).
+ *
+ * @param viewHolder The ViewHolder which should be animated
+ * @param preLayoutInfo The information that was returned from
+ * {@link #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ * @param postLayoutInfo The information that was returned from {@link
+ * #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ *
+ * @return true if a later call to {@link #runPendingAnimations()} is requested,
+ * false otherwise.
+ */
+ public abstract boolean animatePersistence(@NonNull ViewHolder viewHolder,
+ @NonNull ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo);
+
+ /**
+ * Called by the RecyclerView when an adapter item is present both before and after the
+ * layout and RecyclerView has received a {@link Adapter#notifyItemChanged(int)} call
+ * for it. This method may also be called when
+ * {@link Adapter#notifyDataSetChanged()} is called and adapter has stable ids so that
+ * RecyclerView could still rebind views to the same ViewHolders. If viewType changes when
+ * {@link Adapter#notifyDataSetChanged()} is called, this method <b>will not</b> be called,
+ * instead, {@link #animateAppearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)} will be
+ * called for the new ViewHolder and the old one will be recycled.
+ * <p>
+ * If this method is called due to a {@link Adapter#notifyDataSetChanged()} call, there is
+ * a good possibility that item contents didn't really change but it is rebound from the
+ * adapter. {@link DefaultItemAnimator} will skip animating the View if its location on the
+ * screen didn't change and your animator should handle this case as well and avoid creating
+ * unnecessary animations.
+ * <p>
+ * When an item is updated, ItemAnimator has a chance to ask RecyclerView to keep the
+ * previous presentation of the item as-is and supply a new ViewHolder for the updated
+ * presentation (see: {@link #canReuseUpdatedViewHolder(ViewHolder, List)}.
+ * This is useful if you don't know the contents of the Item and would like
+ * to cross-fade the old and the new one ({@link DefaultItemAnimator} uses this technique).
+ * <p>
+ * When you are writing a custom item animator for your layout, it might be more performant
+ * and elegant to re-use the same ViewHolder and animate the content changes manually.
+ * <p>
+ * When {@link Adapter#notifyItemChanged(int)} is called, the Item's view type may change.
+ * If the Item's view type has changed or ItemAnimator returned <code>false</code> for
+ * this ViewHolder when {@link #canReuseUpdatedViewHolder(ViewHolder, List)} was called, the
+ * <code>oldHolder</code> and <code>newHolder</code> will be different ViewHolder instances
+ * which represent the same Item. In that case, only the new ViewHolder is visible
+ * to the LayoutManager but RecyclerView keeps old ViewHolder attached for animations.
+ * <p>
+ * ItemAnimator must call {@link #dispatchAnimationFinished(ViewHolder)} for each distinct
+ * ViewHolder when their animation is complete
+ * (or instantly call {@link #dispatchAnimationFinished(ViewHolder)} if it decides not to
+ * animate the view).
+ * <p>
+ * If oldHolder and newHolder are the same instance, you should call
+ * {@link #dispatchAnimationFinished(ViewHolder)} <b>only once</b>.
+ * <p>
+ * Note that when a ViewHolder both changes and disappears in the same layout pass, the
+ * animation callback method which will be called by the RecyclerView depends on the
+ * ItemAnimator's decision whether to re-use the same ViewHolder or not, and also the
+ * LayoutManager's decision whether to layout the changed version of a disappearing
+ * ViewHolder or not. RecyclerView will call
+ * {@code animateChange} instead of
+ * {@link #animateDisappearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateDisappearance} if and only if the ItemAnimator returns {@code false} from
+ * {@link #canReuseUpdatedViewHolder(ViewHolder) canReuseUpdatedViewHolder} and the
+ * LayoutManager lays out a new disappearing view that holds the updated information.
+ * Built-in LayoutManagers try to avoid laying out updated versions of disappearing views.
+ *
+ * @param oldHolder The ViewHolder before the layout is started, might be the same
+ * instance with newHolder.
+ * @param newHolder The ViewHolder after the layout is finished, might be the same
+ * instance with oldHolder.
+ * @param preLayoutInfo The information that was returned from
+ * {@link #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ * @param postLayoutInfo The information that was returned from {@link
+ * #recordPreLayoutInformation(State, ViewHolder, int, List)}.
+ *
+ * @return true if a later call to {@link #runPendingAnimations()} is requested,
+ * false otherwise.
+ */
+ public abstract boolean animateChange(@NonNull ViewHolder oldHolder,
+ @NonNull ViewHolder newHolder,
+ @NonNull ItemHolderInfo preLayoutInfo, @NonNull ItemHolderInfo postLayoutInfo);
+
+ @AdapterChanges static int buildAdapterChangeFlagsForAnimations(ViewHolder viewHolder) {
+ int flags = viewHolder.mFlags & (FLAG_INVALIDATED | FLAG_REMOVED | FLAG_CHANGED);
+ if (viewHolder.isInvalid()) {
+ return FLAG_INVALIDATED;
+ }
+ if ((flags & FLAG_INVALIDATED) == 0) {
+ final int oldPos = viewHolder.getOldPosition();
+ final int pos = viewHolder.getAdapterPosition();
+ if (oldPos != NO_POSITION && pos != NO_POSITION && oldPos != pos) {
+ flags |= FLAG_MOVED;
+ }
+ }
+ return flags;
+ }
+
+ /**
+ * Called when there are pending animations waiting to be started. This state
+ * is governed by the return values from
+ * {@link #animateAppearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateAppearance()},
+ * {@link #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateChange()}
+ * {@link #animatePersistence(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animatePersistence()}, and
+ * {@link #animateDisappearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateDisappearance()}, which inform the RecyclerView that the ItemAnimator wants to be
+ * called later to start the associated animations. runPendingAnimations() will be scheduled
+ * to be run on the next frame.
+ */
+ public abstract void runPendingAnimations();
+
+ /**
+ * Method called when an animation on a view should be ended immediately.
+ * This could happen when other events, like scrolling, occur, so that
+ * animating views can be quickly put into their proper end locations.
+ * Implementations should ensure that any animations running on the item
+ * are canceled and affected properties are set to their end values.
+ * Also, {@link #dispatchAnimationFinished(ViewHolder)} should be called for each finished
+ * animation since the animations are effectively done when this method is called.
+ *
+ * @param item The item for which an animation should be stopped.
+ */
+ public abstract void endAnimation(ViewHolder item);
+
+ /**
+ * Method called when all item animations should be ended immediately.
+ * This could happen when other events, like scrolling, occur, so that
+ * animating views can be quickly put into their proper end locations.
+ * Implementations should ensure that any animations running on any items
+ * are canceled and affected properties are set to their end values.
+ * Also, {@link #dispatchAnimationFinished(ViewHolder)} should be called for each finished
+ * animation since the animations are effectively done when this method is called.
+ */
+ public abstract void endAnimations();
+
+ /**
+ * Method which returns whether there are any item animations currently running.
+ * This method can be used to determine whether to delay other actions until
+ * animations end.
+ *
+ * @return true if there are any item animations currently running, false otherwise.
+ */
+ public abstract boolean isRunning();
+
+ /**
+ * Method to be called by subclasses when an animation is finished.
+ * <p>
+ * For each call RecyclerView makes to
+ * {@link #animateAppearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateAppearance()},
+ * {@link #animatePersistence(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animatePersistence()}, or
+ * {@link #animateDisappearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateDisappearance()}, there
+ * should
+ * be a matching {@link #dispatchAnimationFinished(ViewHolder)} call by the subclass.
+ * <p>
+ * For {@link #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateChange()}, subclass should call this method for both the <code>oldHolder</code>
+ * and <code>newHolder</code> (if they are not the same instance).
+ *
+ * @param viewHolder The ViewHolder whose animation is finished.
+ * @see #onAnimationFinished(ViewHolder)
+ */
+ public final void dispatchAnimationFinished(ViewHolder viewHolder) {
+ onAnimationFinished(viewHolder);
+ if (mListener != null) {
+ mListener.onAnimationFinished(viewHolder);
+ }
+ }
+
+ /**
+ * Called after {@link #dispatchAnimationFinished(ViewHolder)} is called by the
+ * ItemAnimator.
+ *
+ * @param viewHolder The ViewHolder whose animation is finished. There might still be other
+ * animations running on this ViewHolder.
+ * @see #dispatchAnimationFinished(ViewHolder)
+ */
+ public void onAnimationFinished(ViewHolder viewHolder) {
+ }
+
+ /**
+ * Method to be called by subclasses when an animation is started.
+ * <p>
+ * For each call RecyclerView makes to
+ * {@link #animateAppearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateAppearance()},
+ * {@link #animatePersistence(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animatePersistence()}, or
+ * {@link #animateDisappearance(ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateDisappearance()}, there should be a matching
+ * {@link #dispatchAnimationStarted(ViewHolder)} call by the subclass.
+ * <p>
+ * For {@link #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)
+ * animateChange()}, subclass should call this method for both the <code>oldHolder</code>
+ * and <code>newHolder</code> (if they are not the same instance).
+ * <p>
+ * If your ItemAnimator decides not to animate a ViewHolder, it should call
+ * {@link #dispatchAnimationFinished(ViewHolder)} <b>without</b> calling
+ * {@link #dispatchAnimationStarted(ViewHolder)}.
+ *
+ * @param viewHolder The ViewHolder whose animation is starting.
+ * @see #onAnimationStarted(ViewHolder)
+ */
+ public final void dispatchAnimationStarted(ViewHolder viewHolder) {
+ onAnimationStarted(viewHolder);
+ }
+
+ /**
+ * Called when a new animation is started on the given ViewHolder.
+ *
+ * @param viewHolder The ViewHolder which started animating. Note that the ViewHolder
+ * might already be animating and this might be another animation.
+ * @see #dispatchAnimationStarted(ViewHolder)
+ */
+ public void onAnimationStarted(ViewHolder viewHolder) {
+
+ }
+
+ /**
+ * Like {@link #isRunning()}, this method returns whether there are any item
+ * animations currently running. Additionally, the listener passed in will be called
+ * when there are no item animations running, either immediately (before the method
+ * returns) if no animations are currently running, or when the currently running
+ * animations are {@link #dispatchAnimationsFinished() finished}.
+ *
+ * <p>Note that the listener is transient - it is either called immediately and not
+ * stored at all, or stored only until it is called when running animations
+ * are finished sometime later.</p>
+ *
+ * @param listener A listener to be called immediately if no animations are running
+ * or later when currently-running animations have finished. A null listener is
+ * equivalent to calling {@link #isRunning()}.
+ * @return true if there are any item animations currently running, false otherwise.
+ */
+ public final boolean isRunning(ItemAnimatorFinishedListener listener) {
+ boolean running = isRunning();
+ if (listener != null) {
+ if (!running) {
+ listener.onAnimationsFinished();
+ } else {
+ mFinishedListeners.add(listener);
+ }
+ }
+ return running;
+ }
+
+ /**
+ * When an item is changed, ItemAnimator can decide whether it wants to re-use
+ * the same ViewHolder for animations or RecyclerView should create a copy of the
+ * item and ItemAnimator will use both to run the animation (e.g. cross-fade).
+ * <p>
+ * Note that this method will only be called if the {@link ViewHolder} still has the same
+ * type ({@link Adapter#getItemViewType(int)}). Otherwise, ItemAnimator will always receive
+ * both {@link ViewHolder}s in the
+ * {@link #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)} method.
+ * <p>
+ * If your application is using change payloads, you can override
+ * {@link #canReuseUpdatedViewHolder(ViewHolder, List)} to decide based on payloads.
+ *
+ * @param viewHolder The ViewHolder which represents the changed item's old content.
+ *
+ * @return True if RecyclerView should just rebind to the same ViewHolder or false if
+ * RecyclerView should create a new ViewHolder and pass this ViewHolder to the
+ * ItemAnimator to animate. Default implementation returns <code>true</code>.
+ *
+ * @see #canReuseUpdatedViewHolder(ViewHolder, List)
+ */
+ public boolean canReuseUpdatedViewHolder(@NonNull ViewHolder viewHolder) {
+ return true;
+ }
+
+ /**
+ * When an item is changed, ItemAnimator can decide whether it wants to re-use
+ * the same ViewHolder for animations or RecyclerView should create a copy of the
+ * item and ItemAnimator will use both to run the animation (e.g. cross-fade).
+ * <p>
+ * Note that this method will only be called if the {@link ViewHolder} still has the same
+ * type ({@link Adapter#getItemViewType(int)}). Otherwise, ItemAnimator will always receive
+ * both {@link ViewHolder}s in the
+ * {@link #animateChange(ViewHolder, ViewHolder, ItemHolderInfo, ItemHolderInfo)} method.
+ *
+ * @param viewHolder The ViewHolder which represents the changed item's old content.
+ * @param payloads A non-null list of merged payloads that were sent with change
+ * notifications. Can be empty if the adapter is invalidated via
+ * {@link RecyclerView.Adapter#notifyDataSetChanged()}. The same list of
+ * payloads will be passed into
+ * {@link RecyclerView.Adapter#onBindViewHolder(ViewHolder, int, List)}
+ * method <b>if</b> this method returns <code>true</code>.
+ *
+ * @return True if RecyclerView should just rebind to the same ViewHolder or false if
+ * RecyclerView should create a new ViewHolder and pass this ViewHolder to the
+ * ItemAnimator to animate. Default implementation calls
+ * {@link #canReuseUpdatedViewHolder(ViewHolder)}.
+ *
+ * @see #canReuseUpdatedViewHolder(ViewHolder)
+ */
+ public boolean canReuseUpdatedViewHolder(@NonNull ViewHolder viewHolder,
+ @NonNull List<Object> payloads) {
+ return canReuseUpdatedViewHolder(viewHolder);
+ }
+
+ /**
+ * This method should be called by ItemAnimator implementations to notify
+ * any listeners that all pending and active item animations are finished.
+ */
+ public final void dispatchAnimationsFinished() {
+ final int count = mFinishedListeners.size();
+ for (int i = 0; i < count; ++i) {
+ mFinishedListeners.get(i).onAnimationsFinished();
+ }
+ mFinishedListeners.clear();
+ }
+
+ /**
+ * Returns a new {@link ItemHolderInfo} which will be used to store information about the
+ * ViewHolder. This information will later be passed into <code>animate**</code> methods.
+ * <p>
+ * You can override this method if you want to extend {@link ItemHolderInfo} and provide
+ * your own instances.
+ *
+ * @return A new {@link ItemHolderInfo}.
+ */
+ public ItemHolderInfo obtainHolderInfo() {
+ return new ItemHolderInfo();
+ }
+
+ /**
+ * The interface to be implemented by listeners to animation events from this
+ * ItemAnimator. This is used internally and is not intended for developers to
+ * create directly.
+ */
+ interface ItemAnimatorListener {
+ void onAnimationFinished(ViewHolder item);
+ }
+
+ /**
+ * This interface is used to inform listeners when all pending or running animations
+ * in an ItemAnimator are finished. This can be used, for example, to delay an action
+ * in a data set until currently-running animations are complete.
+ *
+ * @see #isRunning(ItemAnimatorFinishedListener)
+ */
+ public interface ItemAnimatorFinishedListener {
+ /**
+ * Notifies when all pending or running animations in an ItemAnimator are finished.
+ */
+ void onAnimationsFinished();
+ }
+
+ /**
+ * A simple data structure that holds information about an item's bounds.
+ * This information is used in calculating item animations. Default implementation of
+ * {@link #recordPreLayoutInformation(RecyclerView.State, ViewHolder, int, List)} and
+ * {@link #recordPostLayoutInformation(RecyclerView.State, ViewHolder)} returns this data
+ * structure. You can extend this class if you would like to keep more information about
+ * the Views.
+ * <p>
+ * If you want to provide your own implementation but still use `super` methods to record
+ * basic information, you can override {@link #obtainHolderInfo()} to provide your own
+ * instances.
+ */
+ public static class ItemHolderInfo {
+
+ /**
+ * The left edge of the View (excluding decorations)
+ */
+ public int left;
+
+ /**
+ * The top edge of the View (excluding decorations)
+ */
+ public int top;
+
+ /**
+ * The right edge of the View (excluding decorations)
+ */
+ public int right;
+
+ /**
+ * The bottom edge of the View (excluding decorations)
+ */
+ public int bottom;
+
+ /**
+ * The change flags that were passed to
+ * {@link #recordPreLayoutInformation(RecyclerView.State, ViewHolder, int, List)}.
+ */
+ @AdapterChanges
+ public int changeFlags;
+
+ public ItemHolderInfo() {
+ }
+
+ /**
+ * Sets the {@link #left}, {@link #top}, {@link #right} and {@link #bottom} values from
+ * the given ViewHolder. Clears all {@link #changeFlags}.
+ *
+ * @param holder The ViewHolder whose bounds should be copied.
+ * @return This {@link ItemHolderInfo}
+ */
+ public ItemHolderInfo setFrom(RecyclerView.ViewHolder holder) {
+ return setFrom(holder, 0);
+ }
+
+ /**
+ * Sets the {@link #left}, {@link #top}, {@link #right} and {@link #bottom} values from
+ * the given ViewHolder and sets the {@link #changeFlags} to the given flags parameter.
+ *
+ * @param holder The ViewHolder whose bounds should be copied.
+ * @param flags The adapter change flags that were passed into
+ * {@link #recordPreLayoutInformation(RecyclerView.State, ViewHolder, int,
+ * List)}.
+ * @return This {@link ItemHolderInfo}
+ */
+ public ItemHolderInfo setFrom(RecyclerView.ViewHolder holder,
+ @AdapterChanges int flags) {
+ final View view = holder.itemView;
+ this.left = view.getLeft();
+ this.top = view.getTop();
+ this.right = view.getRight();
+ this.bottom = view.getBottom();
+ return this;
+ }
+ }
+ }
+
+ @Override
+ protected int getChildDrawingOrder(int childCount, int i) {
+ if (mChildDrawingOrderCallback == null) {
+ return super.getChildDrawingOrder(childCount, i);
+ } else {
+ return mChildDrawingOrderCallback.onGetChildDrawingOrder(childCount, i);
+ }
+ }
+
+ /**
+ * A callback interface that can be used to alter the drawing order of RecyclerView children.
+ * <p>
+ * It works using the {@link ViewGroup#getChildDrawingOrder(int, int)} method, so any case
+ * that applies to that method also applies to this callback. For example, changing the drawing
+ * order of two views will not have any effect if their elevation values are different since
+ * elevation overrides the result of this callback.
+ */
+ public interface ChildDrawingOrderCallback {
+ /**
+ * Returns the index of the child to draw for this iteration. Override this
+ * if you want to change the drawing order of children. By default, it
+ * returns i.
+ *
+ * @param i The current iteration.
+ * @return The index of the child to draw this iteration.
+ *
+ * @see RecyclerView#setChildDrawingOrderCallback(RecyclerView.ChildDrawingOrderCallback)
+ */
+ int onGetChildDrawingOrder(int childCount, int i);
+ }
+}