core/java/android/widget/AdapterViewAnimator.java

/*
 * Copyright (C) 2010 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 android.widget;

import android.animation.AnimatorInflater;
import android.animation.ObjectAnimator;
import android.content.Context;
import android.content.Intent;
import android.content.res.TypedArray;
import android.os.Handler;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.RemoteViews.OnClickHandler;

import java.util.ArrayList;
import java.util.HashMap;

/**
 * Base class for a {@link AdapterView} that will perform animations
 * when switching between its views.
 *
 * @attr ref android.R.styleable#AdapterViewAnimator_inAnimation
 * @attr ref android.R.styleable#AdapterViewAnimator_outAnimation
 * @attr ref android.R.styleable#AdapterViewAnimator_animateFirstView
 * @attr ref android.R.styleable#AdapterViewAnimator_loopViews
 */
public abstract class AdapterViewAnimator extends AdapterView<Adapter>
        implements RemoteViewsAdapter.RemoteAdapterConnectionCallback, Advanceable {
    private static final String TAG = "RemoteViewAnimator";

    /**
     * The index of the current child, which appears anywhere from the beginning
     * to the end of the current set of children, as specified by {@link #mActiveOffset}
     */
    int mWhichChild = 0;

    /**
     * The index of the child to restore after the asynchronous connection from the
     * RemoteViewsAdapter has been.
     */
    private int mRestoreWhichChild = -1;

    /**
     * Whether or not the first view(s) should be animated in
     */
    boolean mAnimateFirstTime = true;

    /**
     *  Represents where the in the current window of
     *  views the current <code>mDisplayedChild</code> sits
     */
    int mActiveOffset = 0;

    /**
     * The number of views that the {@link AdapterViewAnimator} keeps as children at any
     * given time (not counting views that are pending removal, see {@link #mPreviousViews}).
     */
    int mMaxNumActiveViews = 1;

    /**
     * Map of the children of the {@link AdapterViewAnimator}.
     */
    HashMap<Integer, ViewAndMetaData> mViewsMap = new HashMap<Integer, ViewAndMetaData>();

    /**
     * List of views pending removal from the {@link AdapterViewAnimator}
     */
    ArrayList<Integer> mPreviousViews;

    /**
     * The index, relative to the adapter, of the beginning of the window of views
     */
    int mCurrentWindowStart = 0;

    /**
     * The index, relative to the adapter, of the end of the window of views
     */
    int mCurrentWindowEnd = -1;

    /**
     * The same as {@link #mCurrentWindowStart}, except when the we have bounded
     * {@link #mCurrentWindowStart} to be non-negative
     */
    int mCurrentWindowStartUnbounded = 0;

    /**
     * Listens for data changes from the adapter
     */
    AdapterDataSetObserver mDataSetObserver;

    /**
     * The {@link Adapter} for this {@link AdapterViewAnimator}
     */
    Adapter mAdapter;

    /**
     * The {@link RemoteViewsAdapter} for this {@link AdapterViewAnimator}
     */
    RemoteViewsAdapter mRemoteViewsAdapter;

    /**
     * The remote adapter containing the data to be displayed by this view to be set
     */
    boolean mDeferNotifyDataSetChanged = false;

    /**
     * Specifies whether this is the first time the animator is showing views
     */
    boolean mFirstTime = true;

    /**
     * Specifies if the animator should wrap from 0 to the end and vice versa
     * or have hard boundaries at the beginning and end
     */
    boolean mLoopViews = true;

    /**
     * The width and height of some child, used as a size reference in-case our
     * dimensions are unspecified by the parent.
     */
    int mReferenceChildWidth = -1;
    int mReferenceChildHeight = -1;

    /**
     * In and out animations.
     */
    ObjectAnimator mInAnimation;
    ObjectAnimator mOutAnimation;

    /**
     * Current touch state.
     */
    private int mTouchMode = TOUCH_MODE_NONE;

    /**
     * Private touch states.
     */
    static final int TOUCH_MODE_NONE = 0;
    static final int TOUCH_MODE_DOWN_IN_CURRENT_VIEW = 1;
    static final int TOUCH_MODE_HANDLED = 2;

    private Runnable mPendingCheckForTap;

    private static final int DEFAULT_ANIMATION_DURATION = 200;

    public AdapterViewAnimator(Context context) {
        this(context, null);
    }

    public AdapterViewAnimator(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public AdapterViewAnimator(Context context, AttributeSet attrs, int defStyleAttr) {
        this(context, attrs, defStyleAttr, 0);
    }

    public AdapterViewAnimator(
            Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);

        final TypedArray a = context.obtainStyledAttributes(attrs,
                com.android.internal.R.styleable.AdapterViewAnimator, defStyleAttr, defStyleRes);
        saveAttributeDataForStyleable(context, com.android.internal.R.styleable.AdapterViewAnimator,
                attrs, a, defStyleAttr, defStyleRes);

        int resource = a.getResourceId(
                com.android.internal.R.styleable.AdapterViewAnimator_inAnimation, 0);
        if (resource > 0) {
            setInAnimation(context, resource);
        } else {
            setInAnimation(getDefaultInAnimation());
        }

        resource = a.getResourceId(com.android.internal.R.styleable.AdapterViewAnimator_outAnimation, 0);
        if (resource > 0) {
            setOutAnimation(context, resource);
        } else {
            setOutAnimation(getDefaultOutAnimation());
        }

        boolean flag = a.getBoolean(
                com.android.internal.R.styleable.AdapterViewAnimator_animateFirstView, true);
        setAnimateFirstView(flag);

        mLoopViews = a.getBoolean(
                com.android.internal.R.styleable.AdapterViewAnimator_loopViews, false);

        a.recycle();

        initViewAnimator();
    }

    /**
     * Initialize this {@link AdapterViewAnimator}
     */
    private void initViewAnimator() {
        mPreviousViews = new ArrayList<Integer>();
    }

    class ViewAndMetaData {
        View view;
        int relativeIndex;
        int adapterPosition;
        long itemId;

        ViewAndMetaData(View view, int relativeIndex, int adapterPosition, long itemId) {
            this.view = view;
            this.relativeIndex = relativeIndex;
            this.adapterPosition = adapterPosition;
            this.itemId = itemId;
        }
    }

    /**
     * This method is used by subclasses to configure the animator to display the
     * desired number of views, and specify the offset
     *
     * @param numVisibleViews The number of views the animator keeps in the {@link ViewGroup}
     * @param activeOffset This parameter specifies where the current index ({@link #mWhichChild})
     *        sits within the window. For example if activeOffset is 1, and numVisibleViews is 3,
     *        and {@link #setDisplayedChild(int)} is called with 10, then the effective window will
     *        be the indexes 9, 10, and 11. In the same example, if activeOffset were 0, then the
     *        window would instead contain indexes 10, 11 and 12.
     * @param shouldLoop If the animator is show view 0, and setPrevious() is called, do we
     *        we loop back to the end, or do we do nothing
     */
     void configureViewAnimator(int numVisibleViews, int activeOffset) {
        if (activeOffset > numVisibleViews - 1) {
            // Throw an exception here.
        }
        mMaxNumActiveViews = numVisibleViews;
        mActiveOffset = activeOffset;
        mPreviousViews.clear();
        mViewsMap.clear();
        removeAllViewsInLayout();
        mCurrentWindowStart = 0;
        mCurrentWindowEnd = -1;
    }

    /**
     * This class should be overridden by subclasses to customize view transitions within
     * the set of visible views
     *
     * @param fromIndex The relative index within the window that the view was in, -1 if it wasn't
     *        in the window
     * @param toIndex The relative index within the window that the view is going to, -1 if it is
     *        being removed
     * @param view The view that is being animated
     */
    void transformViewForTransition(int fromIndex, int toIndex, View view, boolean animate) {
        if (fromIndex == -1) {
            mInAnimation.setTarget(view);
            mInAnimation.start();
        } else if (toIndex == -1) {
            mOutAnimation.setTarget(view);
            mOutAnimation.start();
        }
    }

    ObjectAnimator getDefaultInAnimation() {
        ObjectAnimator anim = ObjectAnimator.ofFloat(null, "alpha", 0.0f, 1.0f);
        anim.setDuration(DEFAULT_ANIMATION_DURATION);
        return anim;
    }

    ObjectAnimator getDefaultOutAnimation() {
        ObjectAnimator anim = ObjectAnimator.ofFloat(null, "alpha", 1.0f, 0.0f);
        anim.setDuration(DEFAULT_ANIMATION_DURATION);
        return anim;
    }

    /**
     * Sets which child view will be displayed.
     *
     * @param whichChild the index of the child view to display
     */
    @android.view.RemotableViewMethod
    public void setDisplayedChild(int whichChild) {
        setDisplayedChild(whichChild, true);
    }

    private void setDisplayedChild(int whichChild, boolean animate) {
        if (mAdapter != null) {
            mWhichChild = whichChild;
            if (whichChild >= getWindowSize()) {
                mWhichChild = mLoopViews ? 0 : getWindowSize() - 1;
            } else if (whichChild < 0) {
                mWhichChild = mLoopViews ? getWindowSize() - 1 : 0;
            }

            boolean hasFocus = getFocusedChild() != null;
            // This will clear old focus if we had it
            showOnly(mWhichChild, animate);
            if (hasFocus) {
                // Try to retake focus if we had it
                requestFocus(FOCUS_FORWARD);
            }
        }
    }

    /**
     * To be overridden by subclasses. This method applies a view / index specific
     * transform to the child view.
     *
     * @param child
     * @param relativeIndex
     */
    void applyTransformForChildAtIndex(View child, int relativeIndex) {
    }

    /**
     * Returns the index of the currently displayed child view.
     */
    public int getDisplayedChild() {
        return mWhichChild;
    }

    /**
     * Manually shows the next child.
     */
    public void showNext() {
        setDisplayedChild(mWhichChild + 1);
    }

    /**
     * Manually shows the previous child.
     */
    public void showPrevious() {
        setDisplayedChild(mWhichChild - 1);
    }

    int modulo(int pos, int size) {
        if (size > 0) {
            return (size + (pos % size)) % size;
        } else {
            return 0;
        }
    }

    /**
     * Get the view at this index relative to the current window's start
     *
     * @param relativeIndex Position relative to the current window's start
     * @return View at this index, null if the index is outside the bounds
     */
    View getViewAtRelativeIndex(int relativeIndex) {
        if (relativeIndex >= 0 && relativeIndex <= getNumActiveViews() - 1 && mAdapter != null) {
            int i = modulo(mCurrentWindowStartUnbounded + relativeIndex, getWindowSize());
            if (mViewsMap.get(i) != null) {
                return mViewsMap.get(i).view;
            }
        }
        return null;
    }

    int getNumActiveViews() {
        if (mAdapter != null) {
            return Math.min(getCount() + 1, mMaxNumActiveViews);
        } else {
            return mMaxNumActiveViews;
        }
    }

    int getWindowSize() {
        if (mAdapter != null) {
            int adapterCount = getCount();
            if (adapterCount <= getNumActiveViews() && mLoopViews) {
                return adapterCount*mMaxNumActiveViews;
            } else {
                return adapterCount;
            }
        } else {
            return 0;
        }
    }

    private ViewAndMetaData getMetaDataForChild(View child) {
        for (ViewAndMetaData vm: mViewsMap.values()) {
            if (vm.view == child) {
                return vm;
            }
        }
        return null;
     }

    LayoutParams createOrReuseLayoutParams(View v) {
        final LayoutParams currentLp = v.getLayoutParams();
        if (currentLp != null) {
            return currentLp;
        }
        return new LayoutParams(0, 0);
    }

    void refreshChildren() {
        if (mAdapter == null) return;
        for (int i = mCurrentWindowStart; i <= mCurrentWindowEnd; i++) {
            int index = modulo(i, getWindowSize());

            int adapterCount = getCount();
            // get the fresh child from the adapter
            final View updatedChild = mAdapter.getView(modulo(i, adapterCount), null, this);

            if (updatedChild.getImportantForAccessibility() == IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
                updatedChild.setImportantForAccessibility(IMPORTANT_FOR_ACCESSIBILITY_YES);
            }

            if (mViewsMap.containsKey(index)) {
                final FrameLayout fl = (FrameLayout) mViewsMap.get(index).view;
                // add the new child to the frame, if it exists
                if (updatedChild != null) {
                    // flush out the old child
                    fl.removeAllViewsInLayout();
                    fl.addView(updatedChild);
                }
            }
        }
    }

    /**
     * This method can be overridden so that subclasses can provide a custom frame in which their
     * children can live. For example, StackView adds padding to its childrens' frames so as to
     * accomodate for the highlight effect.
     *
     * @return The FrameLayout into which children can be placed.
     */
    FrameLayout getFrameForChild() {
        return new FrameLayout(mContext);
    }

    /**
     * Shows only the specified child. The other displays Views exit the screen,
     * optionally with the with the {@link #getOutAnimation() out animation} and
     * the specified child enters the screen, optionally with the
     * {@link #getInAnimation() in animation}.
     *
     * @param childIndex The index of the child to be shown.
     * @param animate Whether or not to use the in and out animations, defaults
     *            to true.
     */
    void showOnly(int childIndex, boolean animate) {
        if (mAdapter == null) return;
        final int adapterCount = getCount();
        if (adapterCount == 0) return;

        for (int i = 0; i < mPreviousViews.size(); i++) {
            View viewToRemove = mViewsMap.get(mPreviousViews.get(i)).view;
            mViewsMap.remove(mPreviousViews.get(i));
            viewToRemove.clearAnimation();
            if (viewToRemove instanceof ViewGroup) {
                ViewGroup vg = (ViewGroup) viewToRemove;
                vg.removeAllViewsInLayout();
            }
            // applyTransformForChildAtIndex here just allows for any cleanup
            // associated with this view that may need to be done by a subclass
            applyTransformForChildAtIndex(viewToRemove, -1);

            removeViewInLayout(viewToRemove);
        }
        mPreviousViews.clear();
        int newWindowStartUnbounded = childIndex - mActiveOffset;
        int newWindowEndUnbounded = newWindowStartUnbounded + getNumActiveViews() - 1;
        int newWindowStart = Math.max(0, newWindowStartUnbounded);
        int newWindowEnd = Math.min(adapterCount - 1, newWindowEndUnbounded);

        if (mLoopViews) {
            newWindowStart = newWindowStartUnbounded;
            newWindowEnd = newWindowEndUnbounded;
        }
        int rangeStart = modulo(newWindowStart, getWindowSize());
        int rangeEnd = modulo(newWindowEnd, getWindowSize());

        boolean wrap = false;
        if (rangeStart > rangeEnd) {
            wrap = true;
        }

        // This section clears out any items that are in our active views list
        // but are outside the effective bounds of our window (this is becomes an issue
        // at the extremities of the list, eg. where newWindowStartUnbounded < 0 or
        // newWindowEndUnbounded > adapterCount - 1
        for (Integer index : mViewsMap.keySet()) {
            boolean remove = false;
            if (!wrap && (index < rangeStart || index > rangeEnd)) {
                remove = true;
            } else if (wrap && (index > rangeEnd && index < rangeStart)) {
                remove = true;
            }

            if (remove) {
                View previousView = mViewsMap.get(index).view;
                int oldRelativeIndex = mViewsMap.get(index).relativeIndex;

                mPreviousViews.add(index);
                transformViewForTransition(oldRelativeIndex, -1, previousView, animate);
            }
        }

        // If the window has changed
        if (!(newWindowStart == mCurrentWindowStart && newWindowEnd == mCurrentWindowEnd &&
              newWindowStartUnbounded == mCurrentWindowStartUnbounded)) {
            // Run through the indices in the new range
            for (int i = newWindowStart; i <= newWindowEnd; i++) {

                int index = modulo(i, getWindowSize());
                int oldRelativeIndex;
                if (mViewsMap.containsKey(index)) {
                    oldRelativeIndex = mViewsMap.get(index).relativeIndex;
                } else {
                    oldRelativeIndex = -1;
                }
                int newRelativeIndex = i - newWindowStartUnbounded;

                // If this item is in the current window, great, we just need to apply
                // the transform for it's new relative position in the window, and animate
                // between it's current and new relative positions
                boolean inOldRange = mViewsMap.containsKey(index) && !mPreviousViews.contains(index);

                if (inOldRange) {
                    View view = mViewsMap.get(index).view;
                    mViewsMap.get(index).relativeIndex = newRelativeIndex;
                    applyTransformForChildAtIndex(view, newRelativeIndex);
                    transformViewForTransition(oldRelativeIndex, newRelativeIndex, view, animate);

                // Otherwise this view is new to the window
                } else {
                    // Get the new view from the adapter, add it and apply any transform / animation
                    final int adapterPosition = modulo(i, adapterCount);
                    View newView = mAdapter.getView(adapterPosition, null, this);
                    long itemId = mAdapter.getItemId(adapterPosition);

                    // We wrap the new view in a FrameLayout so as to respect the contract
                    // with the adapter, that is, that we don't modify this view directly
                    FrameLayout fl = getFrameForChild();

                    // If the view from the adapter is null, we still keep an empty frame in place
                    if (newView != null) {
                       fl.addView(newView);
                    }
                    mViewsMap.put(index, new ViewAndMetaData(fl, newRelativeIndex,
                            adapterPosition, itemId));
                    addChild(fl);
                    applyTransformForChildAtIndex(fl, newRelativeIndex);
                    transformViewForTransition(-1, newRelativeIndex, fl, animate);
                }
                mViewsMap.get(index).view.bringToFront();
            }
            mCurrentWindowStart = newWindowStart;
            mCurrentWindowEnd = newWindowEnd;
            mCurrentWindowStartUnbounded = newWindowStartUnbounded;
            if (mRemoteViewsAdapter != null) {
                int adapterStart = modulo(mCurrentWindowStart, adapterCount);
                int adapterEnd = modulo(mCurrentWindowEnd, adapterCount);
                mRemoteViewsAdapter.setVisibleRangeHint(adapterStart, adapterEnd);
            }
        }
        requestLayout();
        invalidate();
    }

    private void addChild(View child) {
        addViewInLayout(child, -1, createOrReuseLayoutParams(child));

        // This code is used to obtain a reference width and height of a child in case we need
        // to decide our own size. TODO: Do we want to update the size of the child that we're
        // using for reference size? If so, when?
        if (mReferenceChildWidth == -1 || mReferenceChildHeight == -1) {
            int measureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
            child.measure(measureSpec, measureSpec);
            mReferenceChildWidth = child.getMeasuredWidth();
            mReferenceChildHeight = child.getMeasuredHeight();
        }
    }

    void showTapFeedback(View v) {
        v.setPressed(true);
    }

    void hideTapFeedback(View v) {
        v.setPressed(false);
    }

    void cancelHandleClick() {
        View v = getCurrentView();
        if (v != null) {
            hideTapFeedback(v);
        }
        mTouchMode = TOUCH_MODE_NONE;
    }

    final class CheckForTap implements Runnable {
        public void run() {
            if (mTouchMode == TOUCH_MODE_DOWN_IN_CURRENT_VIEW) {
                View v = getCurrentView();
                showTapFeedback(v);
            }
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        int action = ev.getAction();
        boolean handled = false;
        switch (action) {
            case MotionEvent.ACTION_DOWN: {
                View v = getCurrentView();
                if (v != null) {
                    if (isTransformedTouchPointInView(ev.getX(), ev.getY(), v, null)) {
                        if (mPendingCheckForTap == null) {
                            mPendingCheckForTap = new CheckForTap();
                        }
                        mTouchMode = TOUCH_MODE_DOWN_IN_CURRENT_VIEW;
                        postDelayed(mPendingCheckForTap, ViewConfiguration.getTapTimeout());
                    }
                }
                break;
            }
            case MotionEvent.ACTION_MOVE: break;
            case MotionEvent.ACTION_POINTER_UP: break;
            case MotionEvent.ACTION_UP: {
                if (mTouchMode == TOUCH_MODE_DOWN_IN_CURRENT_VIEW) {
                    final View v = getCurrentView();
                    final ViewAndMetaData viewData = getMetaDataForChild(v);
                    if (v != null) {
                        if (isTransformedTouchPointInView(ev.getX(), ev.getY(), v, null)) {
                            final Handler handler = getHandler();
                            if (handler != null) {
                                handler.removeCallbacks(mPendingCheckForTap);
                            }
                            showTapFeedback(v);
                            postDelayed(new Runnable() {
                                public void run() {
                                    hideTapFeedback(v);
                                    post(new Runnable() {
                                        public void run() {
                                            if (viewData != null) {
                                                performItemClick(v, viewData.adapterPosition,
                                                        viewData.itemId);
                                            } else {
                                                performItemClick(v, 0, 0);
                                            }
                                        }
                                    });
                                }
                            }, ViewConfiguration.getPressedStateDuration());
                            handled = true;
                        }
                    }
                }
                mTouchMode = TOUCH_MODE_NONE;
                break;
            }
            case MotionEvent.ACTION_CANCEL: {
                View v = getCurrentView();
                if (v != null) {
                    hideTapFeedback(v);
                }
                mTouchMode = TOUCH_MODE_NONE;
            }
        }
        return handled;
    }

    private void measureChildren() {
        final int count = getChildCount();
        final int childWidth = getMeasuredWidth() - mPaddingLeft - mPaddingRight;
        final int childHeight = getMeasuredHeight() - mPaddingTop - mPaddingBottom;

        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            child.measure(MeasureSpec.makeMeasureSpec(childWidth, MeasureSpec.EXACTLY),
                    MeasureSpec.makeMeasureSpec(childHeight, MeasureSpec.EXACTLY));
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSpecSize = MeasureSpec.getSize(heightMeasureSpec);
        final int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
        final int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);

        boolean haveChildRefSize = (mReferenceChildWidth != -1 && mReferenceChildHeight != -1);

        // We need to deal with the case where our parent hasn't told us how
        // big we should be. In this case we try to use the desired size of the first
        // child added.
        if (heightSpecMode == MeasureSpec.UNSPECIFIED) {
            heightSpecSize = haveChildRefSize ? mReferenceChildHeight + mPaddingTop +
                    mPaddingBottom : 0;
        } else if (heightSpecMode == MeasureSpec.AT_MOST) {
            if (haveChildRefSize) {
                int height = mReferenceChildHeight + mPaddingTop + mPaddingBottom;
                if (height > heightSpecSize) {
                    heightSpecSize |= MEASURED_STATE_TOO_SMALL;
                } else {
                    heightSpecSize = height;
                }
            }
        }

        if (widthSpecMode == MeasureSpec.UNSPECIFIED) {
            widthSpecSize = haveChildRefSize ? mReferenceChildWidth + mPaddingLeft +
                    mPaddingRight : 0;
        } else if (heightSpecMode == MeasureSpec.AT_MOST) {
            if (haveChildRefSize) {
                int width = mReferenceChildWidth + mPaddingLeft + mPaddingRight;
                if (width > widthSpecSize) {
                    widthSpecSize |= MEASURED_STATE_TOO_SMALL;
                } else {
                    widthSpecSize = width;
                }
            }
        }

        setMeasuredDimension(widthSpecSize, heightSpecSize);
        measureChildren();
    }

    void checkForAndHandleDataChanged() {
        boolean dataChanged = mDataChanged;
        if (dataChanged) {
            post(new Runnable() {
                public void run() {
                    handleDataChanged();
                    // if the data changes, mWhichChild might be out of the bounds of the adapter
                    // in this case, we reset mWhichChild to the beginning
                    if (mWhichChild >= getWindowSize()) {
                        mWhichChild = 0;

                        showOnly(mWhichChild, false);
                    } else if (mOldItemCount != getCount()) {
                        showOnly(mWhichChild, false);
                    }
                    refreshChildren();
                    requestLayout();
                }
            });
        }
        mDataChanged = false;
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        checkForAndHandleDataChanged();

        final int childCount = getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = getChildAt(i);

            int childRight = mPaddingLeft + child.getMeasuredWidth();
            int childBottom = mPaddingTop + child.getMeasuredHeight();

            child.layout(mPaddingLeft, mPaddingTop, childRight, childBottom);
        }
    }

    static class SavedState extends BaseSavedState {
        int whichChild;

        /**
         * Constructor called from {@link AdapterViewAnimator#onSaveInstanceState()}
         */
        SavedState(Parcelable superState, int whichChild) {
            super(superState);
            this.whichChild = whichChild;
        }

        /**
         * Constructor called from {@link #CREATOR}
         */
        private SavedState(Parcel in) {
            super(in);
            this.whichChild = in.readInt();
        }

        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeInt(this.whichChild);
        }

        @Override
        public String toString() {
            return "AdapterViewAnimator.SavedState{ whichChild = " + this.whichChild + " }";
        }

        public static final Parcelable.Creator<SavedState> CREATOR
                = new Parcelable.Creator<SavedState>() {
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }

            public SavedState[] newArray(int size) {
                return new SavedState[size];
            }
        };
    }

    @Override
    public Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();
        if (mRemoteViewsAdapter != null) {
            mRemoteViewsAdapter.saveRemoteViewsCache();
        }
        return new SavedState(superState, mWhichChild);
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        SavedState ss = (SavedState) state;
        super.onRestoreInstanceState(ss.getSuperState());

        // Here we set mWhichChild in addition to setDisplayedChild
        // We do the former in case mAdapter is null, and hence setDisplayedChild won't
        // set mWhichChild
        mWhichChild = ss.whichChild;

        // When using RemoteAdapters, the async connection process can lead to
        // onRestoreInstanceState to be called before setAdapter(), so we need to save the previous
        // values to restore the list position after we connect, and can skip setting the displayed
        // child until then.
        if (mRemoteViewsAdapter != null && mAdapter == null) {
            mRestoreWhichChild = mWhichChild;
        } else {
            setDisplayedChild(mWhichChild, false);
        }
    }

    /**
     * Returns the View corresponding to the currently displayed child.
     *
     * @return The View currently displayed.
     *
     * @see #getDisplayedChild()
     */
    public View getCurrentView() {
        return getViewAtRelativeIndex(mActiveOffset);
    }

    /**
     * Returns the current animation used to animate a View that enters the screen.
     *
     * @return An Animation or null if none is set.
     *
     * @see #setInAnimation(android.animation.ObjectAnimator)
     * @see #setInAnimation(android.content.Context, int)
     */
    public ObjectAnimator getInAnimation() {
        return mInAnimation;
    }

    /**
     * Specifies the animation used to animate a View that enters the screen.
     *
     * @param inAnimation The animation started when a View enters the screen.
     *
     * @see #getInAnimation()
     * @see #setInAnimation(android.content.Context, int)
     */
    public void setInAnimation(ObjectAnimator inAnimation) {
        mInAnimation = inAnimation;
    }

    /**
     * Returns the current animation used to animate a View that exits the screen.
     *
     * @return An Animation or null if none is set.
     *
     * @see #setOutAnimation(android.animation.ObjectAnimator)
     * @see #setOutAnimation(android.content.Context, int)
     */
    public ObjectAnimator getOutAnimation() {
        return mOutAnimation;
    }

    /**
     * Specifies the animation used to animate a View that exit the screen.
     *
     * @param outAnimation The animation started when a View exit the screen.
     *
     * @see #getOutAnimation()
     * @see #setOutAnimation(android.content.Context, int)
     */
    public void setOutAnimation(ObjectAnimator outAnimation) {
        mOutAnimation = outAnimation;
    }

    /**
     * Specifies the animation used to animate a View that enters the screen.
     *
     * @param context The application's environment.
     * @param resourceID The resource id of the animation.
     *
     * @see #getInAnimation()
     * @see #setInAnimation(android.animation.ObjectAnimator)
     */
    public void setInAnimation(Context context, int resourceID) {
        setInAnimation((ObjectAnimator) AnimatorInflater.loadAnimator(context, resourceID));
    }

    /**
     * Specifies the animation used to animate a View that exit the screen.
     *
     * @param context The application's environment.
     * @param resourceID The resource id of the animation.
     *
     * @see #getOutAnimation()
     * @see #setOutAnimation(android.animation.ObjectAnimator)
     */
    public void setOutAnimation(Context context, int resourceID) {
        setOutAnimation((ObjectAnimator) AnimatorInflater.loadAnimator(context, resourceID));
    }

    /**
     * Indicates whether the current View should be animated the first time
     * the ViewAnimation is displayed.
     *
     * @param animate True to animate the current View the first time it is displayed,
     *                false otherwise.
     */
    public void setAnimateFirstView(boolean animate) {
        mAnimateFirstTime = animate;
    }

    @Override
    public int getBaseline() {
        return (getCurrentView() != null) ? getCurrentView().getBaseline() : super.getBaseline();
    }

    @Override
    public Adapter getAdapter() {
        return mAdapter;
    }

    @Override
    public void setAdapter(Adapter adapter) {
        if (mAdapter != null && mDataSetObserver != null) {
            mAdapter.unregisterDataSetObserver(mDataSetObserver);
        }

        mAdapter = adapter;
        checkFocus();

        if (mAdapter != null) {
            mDataSetObserver = new AdapterDataSetObserver();
            mAdapter.registerDataSetObserver(mDataSetObserver);
            mItemCount = mAdapter.getCount();
        }
        setFocusable(true);
        mWhichChild = 0;
        showOnly(mWhichChild, false);
    }

    /**
     * Sets up this AdapterViewAnimator to use a remote views adapter which connects to a
     * RemoteViewsService through the specified intent.
     *
     * @param intent the intent used to identify the RemoteViewsService for the adapter to
     *        connect to.
     */
    @android.view.RemotableViewMethod(asyncImpl="setRemoteViewsAdapterAsync")
    public void setRemoteViewsAdapter(Intent intent) {
        setRemoteViewsAdapter(intent, false);
    }

    /** @hide **/
    public Runnable setRemoteViewsAdapterAsync(final Intent intent) {
        return new RemoteViewsAdapter.AsyncRemoteAdapterAction(this, intent);
    }

    /** @hide **/
    @Override
    public void setRemoteViewsAdapter(Intent intent, boolean isAsync) {
        // Ensure that we don't already have a RemoteViewsAdapter that is bound to an existing
        // service handling the specified intent.
        if (mRemoteViewsAdapter != null) {
            Intent.FilterComparison fcNew = new Intent.FilterComparison(intent);
            Intent.FilterComparison fcOld = new Intent.FilterComparison(
                    mRemoteViewsAdapter.getRemoteViewsServiceIntent());
            if (fcNew.equals(fcOld)) {
                return;
            }
        }
        mDeferNotifyDataSetChanged = false;
        // Otherwise, create a new RemoteViewsAdapter for binding
        mRemoteViewsAdapter = new RemoteViewsAdapter(getContext(), intent, this, isAsync);
        if (mRemoteViewsAdapter.isDataReady()) {
            setAdapter(mRemoteViewsAdapter);
        }
    }

    /**
     * Sets up the onClickHandler to be used by the RemoteViewsAdapter when inflating RemoteViews
     * 
     * @param handler The OnClickHandler to use when inflating RemoteViews.
     * 
     * @hide
     */
    public void setRemoteViewsOnClickHandler(OnClickHandler handler) {
        // Ensure that we don't already have a RemoteViewsAdapter that is bound to an existing
        // service handling the specified intent.
        if (mRemoteViewsAdapter != null) {
            mRemoteViewsAdapter.setRemoteViewsOnClickHandler(handler);
        }
    }

    @Override
    public void setSelection(int position) {
        setDisplayedChild(position);
    }

    @Override
    public View getSelectedView() {
        return getViewAtRelativeIndex(mActiveOffset);
    }

    /**
     * This defers a notifyDataSetChanged on the pending RemoteViewsAdapter if it has not
     * connected yet.
     */
    public void deferNotifyDataSetChanged() {
        mDeferNotifyDataSetChanged = true;
    }

    /**
     * Called back when the adapter connects to the RemoteViewsService.
     */
    public boolean onRemoteAdapterConnected() {
        if (mRemoteViewsAdapter != mAdapter) {
            setAdapter(mRemoteViewsAdapter);

            if (mDeferNotifyDataSetChanged) {
                mRemoteViewsAdapter.notifyDataSetChanged();
                mDeferNotifyDataSetChanged = false;
            }

            // Restore the previous position (see onRestoreInstanceState)
            if (mRestoreWhichChild > -1) {
                setDisplayedChild(mRestoreWhichChild, false);
                mRestoreWhichChild = -1;
            }
            return false;
        } else if (mRemoteViewsAdapter != null) {
            mRemoteViewsAdapter.superNotifyDataSetChanged();
            return true;
        }
        return false;
    }

    /**
     * Called back when the adapter disconnects from the RemoteViewsService.
     */
    public void onRemoteAdapterDisconnected() {
        // If the remote adapter disconnects, we keep it around
        // since the currently displayed items are still cached.
        // Further, we want the service to eventually reconnect
        // when necessary, as triggered by this view requesting
        // items from the Adapter.
    }

    /**
     * Called by an {@link android.appwidget.AppWidgetHost} in order to advance the current view when
     * it is being used within an app widget.
     */
    public void advance() {
        showNext();
    }

    /**
     * Called by an {@link android.appwidget.AppWidgetHost} to indicate that it will be
     * automatically advancing the views of this {@link AdapterViewAnimator} by calling
     * {@link AdapterViewAnimator#advance()} at some point in the future. This allows subclasses to
     * perform any required setup, for example, to stop automatically advancing their children.
     */
    public void fyiWillBeAdvancedByHostKThx() {
    }

    @Override
    public CharSequence getAccessibilityClassName() {
        return AdapterViewAnimator.class.getName();
    }
}