packages/SystemUI/src/com/android/systemui/recents/grid/RecentsGridActivity.java - platform/frameworks/base - Gitiles

 /*
  * Copyright (C) 2016 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.systemui.recents.grid;

 import static android.app.ActivityManager.StackId.INVALID_STACK_ID;

 import android.app.Activity;
 import android.content.Intent;
 import android.content.res.Configuration;
 import android.content.res.Resources;
 import android.graphics.Point;
 import android.graphics.Rect;
 import android.os.Bundle;
 import android.util.DisplayMetrics;
 import android.view.Gravity;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.WindowManager;
 import android.view.animation.Animation;
 import android.view.animation.AnimationSet;
 import android.view.animation.DecelerateInterpolator;
 import android.view.animation.ScaleAnimation;
 import android.view.animation.TranslateAnimation;
 import android.widget.FrameLayout;
 import android.widget.TextView;

 import com.android.internal.logging.MetricsLogger;
 import com.android.internal.logging.nano.MetricsProto.MetricsEvent;
 import com.android.systemui.R;
 import com.android.systemui.recents.Recents;
 import com.android.systemui.recents.RecentsActivity;
 import com.android.systemui.recents.RecentsActivityLaunchState;
 import com.android.systemui.recents.RecentsConfiguration;
 import com.android.systemui.recents.RecentsImpl;
 import com.android.systemui.recents.events.EventBus;
 import com.android.systemui.recents.events.activity.ConfigurationChangedEvent;
 import com.android.systemui.recents.events.activity.HideRecentsEvent;
 import com.android.systemui.recents.events.activity.LaunchNextTaskRequestEvent;
 import com.android.systemui.recents.events.activity.LaunchTaskEvent;
 import com.android.systemui.recents.events.activity.ToggleRecentsEvent;
 import com.android.systemui.recents.events.component.RecentsVisibilityChangedEvent;
 import com.android.systemui.recents.events.ui.AllTaskViewsDismissedEvent;
 import com.android.systemui.recents.events.ui.DeleteTaskDataEvent;
 import com.android.systemui.recents.events.ui.DismissAllTaskViewsEvent;
 import com.android.systemui.recents.events.ui.DismissTaskViewEvent;
 import com.android.systemui.recents.events.ui.TaskViewDismissedEvent;
 import com.android.systemui.recents.misc.SystemServicesProxy;
 import com.android.systemui.recents.misc.Utilities;
 import com.android.systemui.recents.model.RecentsTaskLoadPlan;
 import com.android.systemui.recents.model.RecentsTaskLoader;
 import com.android.systemui.recents.model.Task;
 import com.android.systemui.recents.model.TaskStack;
 import com.android.systemui.recents.views.TaskView;

 import java.util.ArrayList;
 import java.util.Arrays;

 /**
  * The main grid recents activity started by the RecentsImpl.
  */
 public class RecentsGridActivity extends Activity {
     public final static int MAX_VISIBLE_TASKS = 9;

     private final static String TAG = "RecentsGridActivity";
     private final static int TITLE_BAR_HEIGHT_DP = 64;

     private ArrayList<Integer> mMargins = new ArrayList<>();

     private TaskStack mTaskStack;
     private ArrayList<Task> mTasks = new ArrayList<>();
     private ArrayList<TaskView> mTaskViews = new ArrayList<>();
     private ArrayList<Rect> mTaskViewRects;
     private FrameLayout mRecentsView;
     private TextView mEmptyView;
     private View mClearAllButton;
     private int mLastDisplayOrientation = Configuration.ORIENTATION_UNDEFINED;
     private int mLastDisplayDensity;
     private Rect mDisplayRect = new Rect();
     private LayoutInflater mInflater;
     private boolean mTouchExplorationEnabled;
     private Point mScreenSize;
     private int mTitleBarHeightPx;
     private int mStatusBarHeightPx;
     private int mNavigationBarHeightPx;

     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.recents_grid);
         SystemServicesProxy ssp = Recents.getSystemServices();

         Resources res = getResources();
         Integer[] margins = {
                 res.getDimensionPixelSize(R.dimen.recents_grid_margin_left),
                 res.getDimensionPixelSize(R.dimen.recents_grid_margin_top),
                 res.getDimensionPixelSize(R.dimen.recents_grid_margin_right),
                 res.getDimensionPixelSize(R.dimen.recents_grid_margin_bottom),
         };
         mMargins.addAll(Arrays.asList(margins));

         mInflater = LayoutInflater.from(this);
         Configuration appConfiguration = Utilities.getAppConfiguration(this);
         mDisplayRect = ssp.getDisplayRect();
         mLastDisplayOrientation = appConfiguration.orientation;
         mLastDisplayDensity = appConfiguration.densityDpi;
         mTouchExplorationEnabled = ssp.isTouchExplorationEnabled();
         mScreenSize = new Point();
         getWindowManager().getDefaultDisplay().getRealSize(mScreenSize);
         DisplayMetrics metrics = res.getDisplayMetrics();
         mTitleBarHeightPx = (int) (TITLE_BAR_HEIGHT_DP *
                 ((float) metrics.densityDpi / DisplayMetrics.DENSITY_DEFAULT));
         mStatusBarHeightPx = res.getDimensionPixelSize(R.dimen.status_bar_height);
         mNavigationBarHeightPx = res.getDimensionPixelSize(R.dimen.navigation_bar_height);

         mRecentsView = (FrameLayout) findViewById(R.id.recents_view);
         mRecentsView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE |
                 View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN |
                 View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
         getWindow().getAttributes().privateFlags |=
                 WindowManager.LayoutParams.PRIVATE_FLAG_FORCE_DECOR_VIEW_VISIBILITY;
         mEmptyView = (TextView) mInflater.inflate(R.layout.recents_empty, mRecentsView, false);
         mClearAllButton = findViewById(R.id.button);

         FrameLayout.LayoutParams emptyViewLayoutParams = new FrameLayout.LayoutParams(
             FrameLayout.LayoutParams.MATCH_PARENT, FrameLayout.LayoutParams.WRAP_CONTENT);
         emptyViewLayoutParams.gravity = Gravity.CENTER_VERTICAL | Gravity.CENTER_HORIZONTAL;
         mEmptyView.setLayoutParams(emptyViewLayoutParams);
         mRecentsView.addView(mEmptyView);

         mClearAllButton.setVisibility(View.VISIBLE);
         FrameLayout.LayoutParams lp =
                 (FrameLayout.LayoutParams) mClearAllButton.getLayoutParams();
         lp.gravity = Gravity.END;

         mClearAllButton.setOnClickListener(v -> {
             EventBus.getDefault().send(new DismissAllTaskViewsEvent());
         });

         mRecentsView.setOnClickListener(v -> {
             EventBus.getDefault().send(new HideRecentsEvent(
                     false /* triggeredFromAltTab */, false /* triggeredFromHomeKey */));
         });

         EventBus.getDefault().register(this, RecentsActivity.EVENT_BUS_PRIORITY);
     }

     private TaskView createView() {
         return (TaskView) mInflater.inflate(R.layout.recents_task_view, mRecentsView, false);
     }

     private void removeTaskViews() {
         for (View taskView : mTaskViews) {
             ViewGroup parent = (ViewGroup) taskView.getParent();
             if (parent != null) {
                 parent.removeView(taskView);
             }
         }
     }

     private void clearTaskViews() {
         removeTaskViews();
         mTaskViews.clear();
     }

     private TaskView getChildViewForTask(Task task) {
         for (TaskView tv : mTaskViews) {
             if (tv.getTask() == task) {
                 return tv;
             }
         }
         return null;
     }

     /**
      * Starts animations for each task view to either enlarge it to the size of the screen (when
      * launching a task), or (if {@code reverse} is true, to reduce it from the size of the screen
      * back to its place in the recents layout (when opening recents).
      * @param animationListener An animation listener for executing code before or after the
      *         animations run.
      * @param reverse Whether the blow-up animations should be run in reverse.
      */
     private void startBlowUpAnimations(Animation.AnimationListener animationListener,
             boolean reverse) {
         if (mTaskViews.size() == 0) {
             return;
         }
         int screenWidth = mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE
                 ? mScreenSize.x : mScreenSize.y;
         int screenHeight = mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE
                 ? mScreenSize.y : mScreenSize.x;
         screenHeight -= mStatusBarHeightPx + mNavigationBarHeightPx;
         for (int i = 0; i < mTaskViews.size(); i++) {
             View tv = mTaskViews.get(i);
             AnimationSet animations = new AnimationSet(true /* shareInterpolator */);
             animations.setInterpolator(new DecelerateInterpolator());
             if (i == 0 && animationListener != null) {
                 animations.setAnimationListener(animationListener);
             }
             animations.setFillBefore(reverse);
             animations.setFillAfter(!reverse);
             Rect initialRect = mTaskViewRects.get(mTaskViewRects.size() - 1 - i);
             int xDelta = - initialRect.left;
             int yDelta = - initialRect.top - mTitleBarHeightPx + mStatusBarHeightPx;
             TranslateAnimation translate = new TranslateAnimation(
                     reverse ? xDelta : 0, reverse ? 0 : xDelta,
                     reverse ? yDelta : 0, reverse ? 0 : yDelta);
             translate.setDuration(250);
             animations.addAnimation(translate);


             float xScale = (float) screenWidth / (float) initialRect.width();
             float yScale = (float) screenHeight /
                     ((float) initialRect.height() - mTitleBarHeightPx);
             ScaleAnimation scale = new ScaleAnimation(
                     reverse ? xScale : 1, reverse ? 1 : xScale,
                     reverse ? yScale : 1, reverse ? 1 : yScale,
                     Animation.ABSOLUTE, 0, Animation.ABSOLUTE, mStatusBarHeightPx);
             scale.setDuration(300);
             animations.addAnimation(scale);

             tv.startAnimation(animations);
         }
     }

     private void updateControlVisibility() {
         boolean empty = (mTasks.size() == 0);
         mClearAllButton.setVisibility(empty ? View.INVISIBLE : View.VISIBLE);
         mEmptyView.setVisibility(empty ? View.VISIBLE : View.INVISIBLE);
         if (empty) {
             mEmptyView.bringToFront();
         }
     }

     private void updateModel() {
         RecentsTaskLoader loader = Recents.getTaskLoader();
         RecentsTaskLoadPlan plan = RecentsImpl.consumeInstanceLoadPlan();
         if (plan == null) {
             plan = loader.createLoadPlan(this);
         }
         RecentsConfiguration config = Recents.getConfiguration();
         RecentsActivityLaunchState launchState = config.getLaunchState();
         if (!plan.hasTasks()) {
             loader.preloadTasks(plan, -1, !launchState.launchedFromHome);
         }
         mTaskStack = plan.getTaskStack();
         RecentsTaskLoadPlan.Options loadOpts = new RecentsTaskLoadPlan.Options();
         loadOpts.runningTaskId = launchState.launchedToTaskId;
         loadOpts.numVisibleTasks = MAX_VISIBLE_TASKS;
         loadOpts.numVisibleTaskThumbnails = MAX_VISIBLE_TASKS;
         loader.loadTasks(this, plan, loadOpts);

         mTasks = mTaskStack.getStackTasks();
     }

     private void updateViews() {
         int screenWidth = mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE
                 ? mScreenSize.x : mScreenSize.y;
         int screenHeight = mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE
                 ? mScreenSize.y : mScreenSize.x;
         int paddingPixels = getResources().getDimensionPixelSize(
                 R.dimen.recents_grid_inter_task_padding);
         mTaskViewRects = TaskGridLayoutAlgorithm.getRectsForTaskCount(
                 mTasks.size(), screenWidth, screenHeight, getAppRectRatio(), paddingPixels,
                 mMargins, mTitleBarHeightPx);
         boolean recycleViews = (mTaskViews.size() == mTasks.size());
         if (!recycleViews) {
             clearTaskViews();
         }
         for (int i = 0; i < mTasks.size(); i++) {
             Task task = mTasks.get(i);
             // We keep the same ordering in the model as other Recents flavors (older tasks are
             // first in the stack) so that the logic can be similar, but we reverse the order
             // when placing views on the screen so that most recent tasks are displayed first.
             Rect rect = mTaskViewRects.get(mTaskViewRects.size() - 1 - i);
             TaskView taskView;
             if (recycleViews) {
                 taskView = mTaskViews.get(i);
             } else {
                 taskView = createView();
             }
             taskView.onTaskBound(task, mTouchExplorationEnabled, mLastDisplayOrientation,
                     mDisplayRect);
             Recents.getTaskLoader().loadTaskData(task);
             taskView.setTouchEnabled(true);
             // Show dismiss button right away.
             taskView.startNoUserInteractionAnimation();
             taskView.setLayoutParams(new FrameLayout.LayoutParams(rect.width(), rect.height()));
             taskView.setTranslationX(rect.left);
             taskView.setTranslationY(rect.top);
             if (!recycleViews) {
                 mRecentsView.addView(taskView);
                 mTaskViews.add(taskView);
             }
         }
         updateControlVisibility();
     }

     private float getAppRectRatio() {
         if (mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE) {
             return (float) mScreenSize.x /
                     (float) (mScreenSize.y - mStatusBarHeightPx - mNavigationBarHeightPx);
         } else {
             return (float) mScreenSize.y /
                     (float) (mScreenSize.x - mStatusBarHeightPx - mNavigationBarHeightPx);
         }
     }

     @Override
     protected void onStart() {
         super.onStart();
         EventBus.getDefault().send(new RecentsVisibilityChangedEvent(this, true));
         updateModel();
         updateViews();
         if (mTaskViews.size() > 0) {
             mTaskViews.get(mTaskViews.size() - 1).bringToFront();
         }
         startBlowUpAnimations(new Animation.AnimationListener() {
             @Override
             public void onAnimationStart(Animation animation) { }

             @Override
             public void onAnimationEnd(Animation animation) {
                 updateViews();
             }

             @Override
             public void onAnimationRepeat(Animation animation) { }
         }, true /* reverse */);
     }

     @Override
     protected void onStop() {
         super.onStop();
         EventBus.getDefault().send(new RecentsVisibilityChangedEvent(this, false));
     }

     @Override
     protected void onDestroy() {
         super.onDestroy();
         EventBus.getDefault().unregister(this);
     }

     @Override
     public void onBackPressed() {
         // Back behaves like the recents button so just trigger a toggle event.
         EventBus.getDefault().send(new ToggleRecentsEvent());
     }

     @Override
     public void onConfigurationChanged(Configuration newConfig) {
         super.onConfigurationChanged(newConfig);
         // Notify of the config change.
         Configuration newDeviceConfiguration = Utilities.getAppConfiguration(this);
         mDisplayRect = Recents.getSystemServices().getDisplayRect();
         int numStackTasks = mTaskStack.getStackTaskCount();
         EventBus.getDefault().send(new ConfigurationChangedEvent(false /* fromMultiWindow */,
                 mLastDisplayOrientation != newDeviceConfiguration.orientation,
                 mLastDisplayDensity != newDeviceConfiguration.densityDpi, numStackTasks > 0));
         mLastDisplayOrientation = newDeviceConfiguration.orientation;
         mLastDisplayDensity = newDeviceConfiguration.densityDpi;
         updateViews();
     }

     void dismissRecentsToHome() {
         Intent startMain = new Intent(Intent.ACTION_MAIN);
         startMain.addCategory(Intent.CATEGORY_HOME);
         startActivity(startMain);
     }

     /** Launches the task that recents was launched from if possible. */
     boolean launchPreviousTask() {
         if (mRecentsView != null) {
             Task task = mTaskStack.getLaunchTarget();
             if (task != null) {
                 TaskView taskView = getChildViewForTask(task);
                 EventBus.getDefault().send(new LaunchTaskEvent(taskView, task, null,
                         INVALID_STACK_ID, false));
                 return true;
             }
         }
         return false;
     }

     /** Dismisses recents back to the launch target task. */
     boolean dismissRecentsToLaunchTargetTaskOrHome() {
         SystemServicesProxy ssp = Recents.getSystemServices();
         if (ssp.isRecentsActivityVisible()) {
             // If we can launch the task that Recents was launched from, do that, otherwise go home.
             if (launchPreviousTask()) return true;
             dismissRecentsToHome();
         }
         return false;
     }

     /**** EventBus events ****/

     public final void onBusEvent(HideRecentsEvent event) {
         if (event.triggeredFromAltTab) {
             dismissRecentsToLaunchTargetTaskOrHome();
         } else if (event.triggeredFromHomeKey) {
             dismissRecentsToHome();
         } else {
             // Fall through tap on the background view but not on any of the tasks.
             dismissRecentsToHome();
         }
     }

     public final void onBusEvent(ToggleRecentsEvent event) {
         dismissRecentsToLaunchTargetTaskOrHome();
     }

     public final void onBusEvent(DismissTaskViewEvent event) {
         int taskIndex = mTaskViews.indexOf(event.taskView);
         if (taskIndex != -1) {
             mTasks.remove(taskIndex);
             ((ViewGroup) event.taskView.getParent()).removeView(event.taskView);
             mTaskViews.remove(taskIndex);
             EventBus.getDefault().send(
                     new TaskViewDismissedEvent(event.taskView.getTask(), event.taskView, null));
         }
     }

     public final void onBusEvent(TaskViewDismissedEvent event) {
         mRecentsView.announceForAccessibility(this.getString(
             R.string.accessibility_recents_item_dismissed, event.task.title));
         updateControlVisibility();

         EventBus.getDefault().send(new DeleteTaskDataEvent(event.task));

         MetricsLogger.action(this, MetricsEvent.OVERVIEW_DISMISS,
                 event.task.key.getComponent().toString());
     }

     public final void onBusEvent(DeleteTaskDataEvent event) {
         // Remove any stored data from the loader.
         RecentsTaskLoader loader = Recents.getTaskLoader();
         loader.deleteTaskData(event.task, false);

         // Remove the task from activity manager.
         SystemServicesProxy ssp = Recents.getSystemServices();
         ssp.removeTask(event.task.key.id);
     }

     public final void onBusEvent(final DismissAllTaskViewsEvent event) {
         // Keep track of the tasks which will have their data removed.
         ArrayList<Task> tasks = new ArrayList<>(mTaskStack.getStackTasks());
         mRecentsView.announceForAccessibility(this.getString(
                 R.string.accessibility_recents_all_items_dismissed));
         mTaskStack.removeAllTasks();
         for (int i = tasks.size() - 1; i >= 0; i--) {
             EventBus.getDefault().send(new DeleteTaskDataEvent(tasks.get(i)));
         }
         mTasks = new ArrayList<>();
         updateModel();
         updateViews();

         MetricsLogger.action(this, MetricsEvent.OVERVIEW_DISMISS_ALL);
     }

     public final void onBusEvent(AllTaskViewsDismissedEvent event) {
         SystemServicesProxy ssp = Recents.getSystemServices();
         if (!ssp.hasDockedTask()) {
             dismissRecentsToHome();
         }
     }

     public final void onBusEvent(LaunchNextTaskRequestEvent event) {
         if (mTaskStack.getTaskCount() > 0) {
             Task launchTask = mTaskStack.getNextLaunchTarget();
             TaskView launchTaskView = getChildViewForTask(launchTask);
             if (launchTaskView != null) {
                 EventBus.getDefault().send(new LaunchTaskEvent(launchTaskView,
                         launchTask, null, INVALID_STACK_ID, false /* screenPinningRequested */));
                 MetricsLogger.action(this, MetricsEvent.OVERVIEW_LAUNCH_PREVIOUS_TASK,
                         launchTask.key.getComponent().toString());
                 return;
             }
         }
         // We couldn't find a matching task view, or there are no tasks. Just hide recents back
         // to home.
         EventBus.getDefault().send(new HideRecentsEvent(false, true));
     }

     public final void onBusEvent(LaunchTaskEvent event) {
         event.taskView.bringToFront();
         startActivity(event.task.key.baseIntent);
         // Eventually we should start blow-up animations here, but we need to make sure it's done
         // in parallel with starting the activity so that we don't introduce unneeded latency.
     }
 }
	/*
	* Copyright (C) 2016 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.systemui.recents.grid;

	import static android.app.ActivityManager.StackId.INVALID_STACK_ID;

	import android.app.Activity;
	import android.content.Intent;
	import android.content.res.Configuration;
	import android.content.res.Resources;
	import android.graphics.Point;
	import android.graphics.Rect;
	import android.os.Bundle;
	import android.util.DisplayMetrics;
	import android.view.Gravity;
	import android.view.LayoutInflater;
	import android.view.View;
	import android.view.ViewGroup;
	import android.view.WindowManager;
	import android.view.animation.Animation;
	import android.view.animation.AnimationSet;
	import android.view.animation.DecelerateInterpolator;
	import android.view.animation.ScaleAnimation;
	import android.view.animation.TranslateAnimation;
	import android.widget.FrameLayout;
	import android.widget.TextView;

	import com.android.internal.logging.MetricsLogger;
	import com.android.internal.logging.nano.MetricsProto.MetricsEvent;
	import com.android.systemui.R;
	import com.android.systemui.recents.Recents;
	import com.android.systemui.recents.RecentsActivity;
	import com.android.systemui.recents.RecentsActivityLaunchState;
	import com.android.systemui.recents.RecentsConfiguration;
	import com.android.systemui.recents.RecentsImpl;
	import com.android.systemui.recents.events.EventBus;
	import com.android.systemui.recents.events.activity.ConfigurationChangedEvent;
	import com.android.systemui.recents.events.activity.HideRecentsEvent;
	import com.android.systemui.recents.events.activity.LaunchNextTaskRequestEvent;
	import com.android.systemui.recents.events.activity.LaunchTaskEvent;
	import com.android.systemui.recents.events.activity.ToggleRecentsEvent;
	import com.android.systemui.recents.events.component.RecentsVisibilityChangedEvent;
	import com.android.systemui.recents.events.ui.AllTaskViewsDismissedEvent;
	import com.android.systemui.recents.events.ui.DeleteTaskDataEvent;
	import com.android.systemui.recents.events.ui.DismissAllTaskViewsEvent;
	import com.android.systemui.recents.events.ui.DismissTaskViewEvent;
	import com.android.systemui.recents.events.ui.TaskViewDismissedEvent;
	import com.android.systemui.recents.misc.SystemServicesProxy;
	import com.android.systemui.recents.misc.Utilities;
	import com.android.systemui.recents.model.RecentsTaskLoadPlan;
	import com.android.systemui.recents.model.RecentsTaskLoader;
	import com.android.systemui.recents.model.Task;
	import com.android.systemui.recents.model.TaskStack;
	import com.android.systemui.recents.views.TaskView;

	import java.util.ArrayList;
	import java.util.Arrays;

	/**
	* The main grid recents activity started by the RecentsImpl.
	*/
	public class RecentsGridActivity extends Activity {
	public final static int MAX_VISIBLE_TASKS = 9;

	private final static String TAG = "RecentsGridActivity";
	private final static int TITLE_BAR_HEIGHT_DP = 64;

	private ArrayList<Integer> mMargins = new ArrayList<>();

	private TaskStack mTaskStack;
	private ArrayList<Task> mTasks = new ArrayList<>();
	private ArrayList<TaskView> mTaskViews = new ArrayList<>();
	private ArrayList<Rect> mTaskViewRects;
	private FrameLayout mRecentsView;
	private TextView mEmptyView;
	private View mClearAllButton;
	private int mLastDisplayOrientation = Configuration.ORIENTATION_UNDEFINED;
	private int mLastDisplayDensity;
	private Rect mDisplayRect = new Rect();
	private LayoutInflater mInflater;
	private boolean mTouchExplorationEnabled;
	private Point mScreenSize;
	private int mTitleBarHeightPx;
	private int mStatusBarHeightPx;
	private int mNavigationBarHeightPx;

	@Override
	public void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.recents_grid);
	SystemServicesProxy ssp = Recents.getSystemServices();

	Resources res = getResources();
	Integer[] margins = {
	res.getDimensionPixelSize(R.dimen.recents_grid_margin_left),
	res.getDimensionPixelSize(R.dimen.recents_grid_margin_top),
	res.getDimensionPixelSize(R.dimen.recents_grid_margin_right),
	res.getDimensionPixelSize(R.dimen.recents_grid_margin_bottom),
	};
	mMargins.addAll(Arrays.asList(margins));

	mInflater = LayoutInflater.from(this);
	Configuration appConfiguration = Utilities.getAppConfiguration(this);
	mDisplayRect = ssp.getDisplayRect();
	mLastDisplayOrientation = appConfiguration.orientation;
	mLastDisplayDensity = appConfiguration.densityDpi;
	mTouchExplorationEnabled = ssp.isTouchExplorationEnabled();
	mScreenSize = new Point();
	getWindowManager().getDefaultDisplay().getRealSize(mScreenSize);
	DisplayMetrics metrics = res.getDisplayMetrics();
	mTitleBarHeightPx = (int) (TITLE_BAR_HEIGHT_DP *
	((float) metrics.densityDpi / DisplayMetrics.DENSITY_DEFAULT));
	mStatusBarHeightPx = res.getDimensionPixelSize(R.dimen.status_bar_height);
	mNavigationBarHeightPx = res.getDimensionPixelSize(R.dimen.navigation_bar_height);

	mRecentsView = (FrameLayout) findViewById(R.id.recents_view);
	mRecentsView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE \|
	View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN \|
	View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
	getWindow().getAttributes().privateFlags \|=
	WindowManager.LayoutParams.PRIVATE_FLAG_FORCE_DECOR_VIEW_VISIBILITY;
	mEmptyView = (TextView) mInflater.inflate(R.layout.recents_empty, mRecentsView, false);
	mClearAllButton = findViewById(R.id.button);

	FrameLayout.LayoutParams emptyViewLayoutParams = new FrameLayout.LayoutParams(
	FrameLayout.LayoutParams.MATCH_PARENT, FrameLayout.LayoutParams.WRAP_CONTENT);
	emptyViewLayoutParams.gravity = Gravity.CENTER_VERTICAL \| Gravity.CENTER_HORIZONTAL;
	mEmptyView.setLayoutParams(emptyViewLayoutParams);
	mRecentsView.addView(mEmptyView);

	mClearAllButton.setVisibility(View.VISIBLE);
	FrameLayout.LayoutParams lp =
	(FrameLayout.LayoutParams) mClearAllButton.getLayoutParams();
	lp.gravity = Gravity.END;

	mClearAllButton.setOnClickListener(v -> {
	EventBus.getDefault().send(new DismissAllTaskViewsEvent());
	});

	mRecentsView.setOnClickListener(v -> {
	EventBus.getDefault().send(new HideRecentsEvent(
	false /* triggeredFromAltTab /, false / triggeredFromHomeKey */));
	});

	EventBus.getDefault().register(this, RecentsActivity.EVENT_BUS_PRIORITY);
	}

	private TaskView createView() {
	return (TaskView) mInflater.inflate(R.layout.recents_task_view, mRecentsView, false);
	}

	private void removeTaskViews() {
	for (View taskView : mTaskViews) {
	ViewGroup parent = (ViewGroup) taskView.getParent();
	if (parent != null) {
	parent.removeView(taskView);
	}
	}
	}

	private void clearTaskViews() {
	removeTaskViews();
	mTaskViews.clear();
	}

	private TaskView getChildViewForTask(Task task) {
	for (TaskView tv : mTaskViews) {
	if (tv.getTask() == task) {
	return tv;
	}
	}
	return null;
	}

	/**
	* Starts animations for each task view to either enlarge it to the size of the screen (when
	* launching a task), or (if {@code reverse} is true, to reduce it from the size of the screen
	* back to its place in the recents layout (when opening recents).
	* @param animationListener An animation listener for executing code before or after the
	* animations run.
	* @param reverse Whether the blow-up animations should be run in reverse.
	*/
	private void startBlowUpAnimations(Animation.AnimationListener animationListener,
	boolean reverse) {
	if (mTaskViews.size() == 0) {
	return;
	}
	int screenWidth = mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE
	? mScreenSize.x : mScreenSize.y;
	int screenHeight = mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE
	? mScreenSize.y : mScreenSize.x;
	screenHeight -= mStatusBarHeightPx + mNavigationBarHeightPx;
	for (int i = 0; i < mTaskViews.size(); i++) {
	View tv = mTaskViews.get(i);
	AnimationSet animations = new AnimationSet(true /* shareInterpolator */);
	animations.setInterpolator(new DecelerateInterpolator());
	if (i == 0 && animationListener != null) {
	animations.setAnimationListener(animationListener);
	}
	animations.setFillBefore(reverse);
	animations.setFillAfter(!reverse);
	Rect initialRect = mTaskViewRects.get(mTaskViewRects.size() - 1 - i);
	int xDelta = - initialRect.left;
	int yDelta = - initialRect.top - mTitleBarHeightPx + mStatusBarHeightPx;
	TranslateAnimation translate = new TranslateAnimation(
	reverse ? xDelta : 0, reverse ? 0 : xDelta,
	reverse ? yDelta : 0, reverse ? 0 : yDelta);
	translate.setDuration(250);
	animations.addAnimation(translate);


	float xScale = (float) screenWidth / (float) initialRect.width();
	float yScale = (float) screenHeight /
	((float) initialRect.height() - mTitleBarHeightPx);
	ScaleAnimation scale = new ScaleAnimation(
	reverse ? xScale : 1, reverse ? 1 : xScale,
	reverse ? yScale : 1, reverse ? 1 : yScale,
	Animation.ABSOLUTE, 0, Animation.ABSOLUTE, mStatusBarHeightPx);
	scale.setDuration(300);
	animations.addAnimation(scale);

	tv.startAnimation(animations);
	}
	}

	private void updateControlVisibility() {
	boolean empty = (mTasks.size() == 0);
	mClearAllButton.setVisibility(empty ? View.INVISIBLE : View.VISIBLE);
	mEmptyView.setVisibility(empty ? View.VISIBLE : View.INVISIBLE);
	if (empty) {
	mEmptyView.bringToFront();
	}
	}

	private void updateModel() {
	RecentsTaskLoader loader = Recents.getTaskLoader();
	RecentsTaskLoadPlan plan = RecentsImpl.consumeInstanceLoadPlan();
	if (plan == null) {
	plan = loader.createLoadPlan(this);
	}
	RecentsConfiguration config = Recents.getConfiguration();
	RecentsActivityLaunchState launchState = config.getLaunchState();
	if (!plan.hasTasks()) {
	loader.preloadTasks(plan, -1, !launchState.launchedFromHome);
	}
	mTaskStack = plan.getTaskStack();
	RecentsTaskLoadPlan.Options loadOpts = new RecentsTaskLoadPlan.Options();
	loadOpts.runningTaskId = launchState.launchedToTaskId;
	loadOpts.numVisibleTasks = MAX_VISIBLE_TASKS;
	loadOpts.numVisibleTaskThumbnails = MAX_VISIBLE_TASKS;
	loader.loadTasks(this, plan, loadOpts);

	mTasks = mTaskStack.getStackTasks();
	}

	private void updateViews() {
	int screenWidth = mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE
	? mScreenSize.x : mScreenSize.y;
	int screenHeight = mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE
	? mScreenSize.y : mScreenSize.x;
	int paddingPixels = getResources().getDimensionPixelSize(
	R.dimen.recents_grid_inter_task_padding);
	mTaskViewRects = TaskGridLayoutAlgorithm.getRectsForTaskCount(
	mTasks.size(), screenWidth, screenHeight, getAppRectRatio(), paddingPixels,
	mMargins, mTitleBarHeightPx);
	boolean recycleViews = (mTaskViews.size() == mTasks.size());
	if (!recycleViews) {
	clearTaskViews();
	}
	for (int i = 0; i < mTasks.size(); i++) {
	Task task = mTasks.get(i);
	// We keep the same ordering in the model as other Recents flavors (older tasks are
	// first in the stack) so that the logic can be similar, but we reverse the order
	// when placing views on the screen so that most recent tasks are displayed first.
	Rect rect = mTaskViewRects.get(mTaskViewRects.size() - 1 - i);
	TaskView taskView;
	if (recycleViews) {
	taskView = mTaskViews.get(i);
	} else {
	taskView = createView();
	}
	taskView.onTaskBound(task, mTouchExplorationEnabled, mLastDisplayOrientation,
	mDisplayRect);
	Recents.getTaskLoader().loadTaskData(task);
	taskView.setTouchEnabled(true);
	// Show dismiss button right away.
	taskView.startNoUserInteractionAnimation();
	taskView.setLayoutParams(new FrameLayout.LayoutParams(rect.width(), rect.height()));
	taskView.setTranslationX(rect.left);
	taskView.setTranslationY(rect.top);
	if (!recycleViews) {
	mRecentsView.addView(taskView);
	mTaskViews.add(taskView);
	}
	}
	updateControlVisibility();
	}

	private float getAppRectRatio() {
	if (mLastDisplayOrientation == Configuration.ORIENTATION_LANDSCAPE) {
	return (float) mScreenSize.x /
	(float) (mScreenSize.y - mStatusBarHeightPx - mNavigationBarHeightPx);
	} else {
	return (float) mScreenSize.y /
	(float) (mScreenSize.x - mStatusBarHeightPx - mNavigationBarHeightPx);
	}
	}

	@Override
	protected void onStart() {
	super.onStart();
	EventBus.getDefault().send(new RecentsVisibilityChangedEvent(this, true));
	updateModel();
	updateViews();
	if (mTaskViews.size() > 0) {
	mTaskViews.get(mTaskViews.size() - 1).bringToFront();
	}
	startBlowUpAnimations(new Animation.AnimationListener() {
	@Override
	public void onAnimationStart(Animation animation) { }

	@Override
	public void onAnimationEnd(Animation animation) {
	updateViews();
	}

	@Override
	public void onAnimationRepeat(Animation animation) { }
	}, true /* reverse */);
	}

	@Override
	protected void onStop() {
	super.onStop();
	EventBus.getDefault().send(new RecentsVisibilityChangedEvent(this, false));
	}

	@Override
	protected void onDestroy() {
	super.onDestroy();
	EventBus.getDefault().unregister(this);
	}

	@Override
	public void onBackPressed() {
	// Back behaves like the recents button so just trigger a toggle event.
	EventBus.getDefault().send(new ToggleRecentsEvent());
	}

	@Override
	public void onConfigurationChanged(Configuration newConfig) {
	super.onConfigurationChanged(newConfig);
	// Notify of the config change.
	Configuration newDeviceConfiguration = Utilities.getAppConfiguration(this);
	mDisplayRect = Recents.getSystemServices().getDisplayRect();
	int numStackTasks = mTaskStack.getStackTaskCount();
	EventBus.getDefault().send(new ConfigurationChangedEvent(false /* fromMultiWindow */,
	mLastDisplayOrientation != newDeviceConfiguration.orientation,
	mLastDisplayDensity != newDeviceConfiguration.densityDpi, numStackTasks > 0));
	mLastDisplayOrientation = newDeviceConfiguration.orientation;
	mLastDisplayDensity = newDeviceConfiguration.densityDpi;
	updateViews();
	}

	void dismissRecentsToHome() {
	Intent startMain = new Intent(Intent.ACTION_MAIN);
	startMain.addCategory(Intent.CATEGORY_HOME);
	startActivity(startMain);
	}

	/** Launches the task that recents was launched from if possible. */
	boolean launchPreviousTask() {
	if (mRecentsView != null) {
	Task task = mTaskStack.getLaunchTarget();
	if (task != null) {
	TaskView taskView = getChildViewForTask(task);
	EventBus.getDefault().send(new LaunchTaskEvent(taskView, task, null,
	INVALID_STACK_ID, false));
	return true;
	}
	}
	return false;
	}

	/** Dismisses recents back to the launch target task. */
	boolean dismissRecentsToLaunchTargetTaskOrHome() {
	SystemServicesProxy ssp = Recents.getSystemServices();
	if (ssp.isRecentsActivityVisible()) {
	// If we can launch the task that Recents was launched from, do that, otherwise go home.
	if (launchPreviousTask()) return true;
	dismissRecentsToHome();
	}
	return false;
	}

	/** EventBus events **/

	public final void onBusEvent(HideRecentsEvent event) {
	if (event.triggeredFromAltTab) {
	dismissRecentsToLaunchTargetTaskOrHome();
	} else if (event.triggeredFromHomeKey) {
	dismissRecentsToHome();
	} else {
	// Fall through tap on the background view but not on any of the tasks.
	dismissRecentsToHome();
	}
	}

	public final void onBusEvent(ToggleRecentsEvent event) {
	dismissRecentsToLaunchTargetTaskOrHome();
	}

	public final void onBusEvent(DismissTaskViewEvent event) {
	int taskIndex = mTaskViews.indexOf(event.taskView);
	if (taskIndex != -1) {
	mTasks.remove(taskIndex);
	((ViewGroup) event.taskView.getParent()).removeView(event.taskView);
	mTaskViews.remove(taskIndex);
	EventBus.getDefault().send(
	new TaskViewDismissedEvent(event.taskView.getTask(), event.taskView, null));
	}
	}

	public final void onBusEvent(TaskViewDismissedEvent event) {
	mRecentsView.announceForAccessibility(this.getString(
	R.string.accessibility_recents_item_dismissed, event.task.title));
	updateControlVisibility();

	EventBus.getDefault().send(new DeleteTaskDataEvent(event.task));

	MetricsLogger.action(this, MetricsEvent.OVERVIEW_DISMISS,
	event.task.key.getComponent().toString());
	}

	public final void onBusEvent(DeleteTaskDataEvent event) {
	// Remove any stored data from the loader.
	RecentsTaskLoader loader = Recents.getTaskLoader();
	loader.deleteTaskData(event.task, false);

	// Remove the task from activity manager.
	SystemServicesProxy ssp = Recents.getSystemServices();
	ssp.removeTask(event.task.key.id);
	}

	public final void onBusEvent(final DismissAllTaskViewsEvent event) {
	// Keep track of the tasks which will have their data removed.
	ArrayList<Task> tasks = new ArrayList<>(mTaskStack.getStackTasks());
	mRecentsView.announceForAccessibility(this.getString(
	R.string.accessibility_recents_all_items_dismissed));
	mTaskStack.removeAllTasks();
	for (int i = tasks.size() - 1; i >= 0; i--) {
	EventBus.getDefault().send(new DeleteTaskDataEvent(tasks.get(i)));
	}
	mTasks = new ArrayList<>();
	updateModel();
	updateViews();

	MetricsLogger.action(this, MetricsEvent.OVERVIEW_DISMISS_ALL);
	}

	public final void onBusEvent(AllTaskViewsDismissedEvent event) {
	SystemServicesProxy ssp = Recents.getSystemServices();
	if (!ssp.hasDockedTask()) {
	dismissRecentsToHome();
	}
	}

	public final void onBusEvent(LaunchNextTaskRequestEvent event) {
	if (mTaskStack.getTaskCount() > 0) {
	Task launchTask = mTaskStack.getNextLaunchTarget();
	TaskView launchTaskView = getChildViewForTask(launchTask);
	if (launchTaskView != null) {
	EventBus.getDefault().send(new LaunchTaskEvent(launchTaskView,
	launchTask, null, INVALID_STACK_ID, false /* screenPinningRequested */));
	MetricsLogger.action(this, MetricsEvent.OVERVIEW_LAUNCH_PREVIOUS_TASK,
	launchTask.key.getComponent().toString());
	return;
	}
	}
	// We couldn't find a matching task view, or there are no tasks. Just hide recents back
	// to home.
	EventBus.getDefault().send(new HideRecentsEvent(false, true));
	}

	public final void onBusEvent(LaunchTaskEvent event) {
	event.taskView.bringToFront();
	startActivity(event.task.key.baseIntent);
	// Eventually we should start blow-up animations here, but we need to make sure it's done
	// in parallel with starting the activity so that we don't introduce unneeded latency.
	}
	}