Merge changes from topic "presubmit-am-1224af9ca3f341a895e4bc19976e2bb8" into tm-dev

* changes:
  Fix recents animation flicker
  Fix janky overview animation.
diff --git a/quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java b/quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java
index 5acce89..13389c0 100644
--- a/quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java
+++ b/quickstep/src/com/android/quickstep/AbsSwipeUpHandler.java
@@ -22,6 +22,7 @@
 
 import static com.android.launcher3.BaseActivity.INVISIBLE_BY_STATE_HANDLER;
 import static com.android.launcher3.BaseActivity.STATE_HANDLER_INVISIBILITY_FLAGS;
+import static com.android.launcher3.PagedView.INVALID_PAGE;
 import static com.android.launcher3.anim.Interpolators.ACCEL_DEACCEL;
 import static com.android.launcher3.anim.Interpolators.DEACCEL;
 import static com.android.launcher3.anim.Interpolators.OVERSHOOT_1_2;
@@ -66,6 +67,7 @@
 import android.os.Build;
 import android.os.IBinder;
 import android.os.SystemClock;
+import android.util.Log;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.View.OnApplyWindowInsetsListener;
@@ -926,7 +928,13 @@
             mLogDirectionUpOrLeft = velocity.x < 0;
         }
         mDownPos = downPos;
-        handleNormalGestureEnd(endVelocity, isFling, velocity, false /* isCancel */);
+        Runnable handleNormalGestureEndCallback = () ->
+                handleNormalGestureEnd(endVelocity, isFling, velocity, /* isCancel= */ false);
+        if (mRecentsView != null) {
+            mRecentsView.runOnPageScrollsInitialized(handleNormalGestureEndCallback);
+        } else {
+            handleNormalGestureEndCallback.run();
+        }
     }
 
     private void endRunningWindowAnim(boolean cancel) {
@@ -1130,6 +1138,13 @@
         } else if (endTarget == RECENTS) {
             if (mRecentsView != null) {
                 int nearestPage = mRecentsView.getDestinationPage();
+                if (nearestPage == INVALID_PAGE) {
+                    // Allow the snap to invalid page to catch future error cases.
+                    Log.e(TAG,
+                            "RecentsView destination page is invalid",
+                            new IllegalStateException());
+                }
+
                 boolean isScrolling = false;
                 if (mRecentsView.getNextPage() != nearestPage) {
                     // We shouldn't really scroll to the next page when swiping up to recents.
diff --git a/quickstep/src/com/android/quickstep/BaseActivityInterface.java b/quickstep/src/com/android/quickstep/BaseActivityInterface.java
index 48127c0..6745246 100644
--- a/quickstep/src/com/android/quickstep/BaseActivityInterface.java
+++ b/quickstep/src/com/android/quickstep/BaseActivityInterface.java
@@ -84,6 +84,8 @@
 
     private STATE_TYPE mTargetState;
 
+    @Nullable private Runnable mOnInitBackgroundStateUICallback = null;
+
     protected BaseActivityInterface(boolean rotationSupportedByActivity,
             STATE_TYPE overviewState, STATE_TYPE backgroundState) {
         this.rotationSupportedByActivity = rotationSupportedByActivity;
@@ -408,6 +410,21 @@
         return null;
     }
 
+    protected void runOnInitBackgroundStateUI(Runnable callback) {
+        mOnInitBackgroundStateUICallback = callback;
+        ACTIVITY_TYPE activity = getCreatedActivity();
+        if (activity != null && activity.getStateManager().getState() == mBackgroundState) {
+            onInitBackgroundStateUI();
+        }
+    }
+
+    private void onInitBackgroundStateUI() {
+        if (mOnInitBackgroundStateUICallback != null) {
+            mOnInitBackgroundStateUICallback.run();
+            mOnInitBackgroundStateUICallback = null;
+        }
+    }
+
     public interface AnimationFactory {
 
         void createActivityInterface(long transitionLength);
@@ -447,13 +464,14 @@
             mStartState = mActivity.getStateManager().getState();
         }
 
-        protected ACTIVITY_TYPE initUI() {
+        protected ACTIVITY_TYPE initBackgroundStateUI() {
             STATE_TYPE resetState = mStartState;
             if (mStartState.shouldDisableRestore()) {
                 resetState = mActivity.getStateManager().getRestState();
             }
             mActivity.getStateManager().setRestState(resetState);
             mActivity.getStateManager().goToState(mBackgroundState, false);
+            onInitBackgroundStateUI();
             return mActivity;
         }
 
diff --git a/quickstep/src/com/android/quickstep/FallbackActivityInterface.java b/quickstep/src/com/android/quickstep/FallbackActivityInterface.java
index 7feec2c..ba61574 100644
--- a/quickstep/src/com/android/quickstep/FallbackActivityInterface.java
+++ b/quickstep/src/com/android/quickstep/FallbackActivityInterface.java
@@ -89,7 +89,7 @@
             boolean activityVisible, Consumer<AnimatorControllerWithResistance> callback) {
         notifyRecentsOfOrientation(deviceState.getRotationTouchHelper());
         DefaultAnimationFactory factory = new DefaultAnimationFactory(callback);
-        factory.initUI();
+        factory.initBackgroundStateUI();
         return factory;
     }
 
diff --git a/quickstep/src/com/android/quickstep/LauncherActivityInterface.java b/quickstep/src/com/android/quickstep/LauncherActivityInterface.java
index 10a3a2e..c13b95f 100644
--- a/quickstep/src/com/android/quickstep/LauncherActivityInterface.java
+++ b/quickstep/src/com/android/quickstep/LauncherActivityInterface.java
@@ -135,7 +135,7 @@
             }
         };
 
-        BaseQuickstepLauncher launcher = factory.initUI();
+        BaseQuickstepLauncher launcher = factory.initBackgroundStateUI();
         // Since all apps is not visible, we can safely reset the scroll position.
         // This ensures then the next swipe up to all-apps starts from scroll 0.
         launcher.getAppsView().reset(false /* animate */);
diff --git a/quickstep/src/com/android/quickstep/OverviewCommandHelper.java b/quickstep/src/com/android/quickstep/OverviewCommandHelper.java
index 42f9eb6..dffdc5a 100644
--- a/quickstep/src/com/android/quickstep/OverviewCommandHelper.java
+++ b/quickstep/src/com/android/quickstep/OverviewCommandHelper.java
@@ -217,7 +217,8 @@
             @Override
             public void onRecentsAnimationStart(RecentsAnimationController controller,
                     RecentsAnimationTargets targets) {
-                interactionHandler.onGestureEnded(0, new PointF(), new PointF());
+                activityInterface.runOnInitBackgroundStateUI(() ->
+                        interactionHandler.onGestureEnded(0, new PointF(), new PointF()));
                 cmd.removeListener(this);
             }
 
diff --git a/quickstep/src/com/android/quickstep/views/RecentsView.java b/quickstep/src/com/android/quickstep/views/RecentsView.java
index d4c5b8f..b634518 100644
--- a/quickstep/src/com/android/quickstep/views/RecentsView.java
+++ b/quickstep/src/com/android/quickstep/views/RecentsView.java
@@ -946,7 +946,7 @@
                 mHasVisibleTaskData.delete(i);
             }
             if (child instanceof GroupedTaskView) {
-                mGroupedTaskViewPool.recycle((GroupedTaskView)taskView);
+                mGroupedTaskViewPool.recycle((GroupedTaskView) taskView);
             } else {
                 mTaskViewPool.recycle(taskView);
             }
@@ -1855,17 +1855,18 @@
         if (!mActivity.getDeviceProfile().isTablet) {
             return super.getDestinationPage(scaledScroll);
         }
-
-        final int childCount = getChildCount();
-        if (mPageScrolls == null || childCount != mPageScrolls.length) {
-            return -1;
+        if (!pageScrollsInitialized()) {
+            Log.e(TAG,
+                    "Cannot get destination page: RecentsView not properly initialized",
+                    new IllegalStateException());
+            return INVALID_PAGE;
         }
 
         // When in tablet with variable task width, return the page which scroll is closest to
         // screenStart instead of page nearest to center of screen.
         int minDistanceFromScreenStart = Integer.MAX_VALUE;
-        int minDistanceFromScreenStartIndex = -1;
-        for (int i = 0; i < childCount; ++i) {
+        int minDistanceFromScreenStartIndex = INVALID_PAGE;
+        for (int i = 0; i < getChildCount(); ++i) {
             int distanceFromScreenStart = Math.abs(mPageScrolls[i] - scaledScroll);
             if (distanceFromScreenStart < minDistanceFromScreenStart) {
                 minDistanceFromScreenStart = distanceFromScreenStart;
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index 2ad1d47..ad87451 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -1279,13 +1279,16 @@
      * @param info The data structure describing the shortcut.
      */
     View createShortcut(WorkspaceItemInfo info) {
-        return createShortcut((ViewGroup) mWorkspace.getChildAt(mWorkspace.getCurrentPage()), info);
+        // This can be called before PagedView#pageScrollsInitialized returns true, so use the
+        // first page, which we always assume to be present.
+        return createShortcut((ViewGroup) mWorkspace.getChildAt(0), info);
     }
 
     /**
      * Creates a view representing a shortcut inflated from the specified resource.
      *
-     * @param parent The group the shortcut belongs to.
+     * @param parent The group the shortcut belongs to. This is not necessarily the group where
+     *               the shortcut should be added.
      * @param info   The data structure describing the shortcut.
      * @return A View inflated from layoutResId.
      */
diff --git a/src/com/android/launcher3/PagedView.java b/src/com/android/launcher3/PagedView.java
index 0a1d25c..95a8a2a 100644
--- a/src/com/android/launcher3/PagedView.java
+++ b/src/com/android/launcher3/PagedView.java
@@ -129,7 +129,10 @@
     private boolean mAllowEasyFling;
     protected PagedOrientationHandler mOrientationHandler = PagedOrientationHandler.PORTRAIT;
 
-    protected int[] mPageScrolls;
+    private final ArrayList<Runnable> mOnPageScrollsInitializedCallbacks = new ArrayList<>();
+
+    // We should always check pageScrollsInitialized() is true when using mPageScrolls.
+    @Nullable protected int[] mPageScrolls = null;
     private boolean mIsBeingDragged;
 
     // The amount of movement to begin scrolling
@@ -684,14 +687,37 @@
         setMeasuredDimension(widthSize, heightSize);
     }
 
+    /** Returns true iff this PagedView's scroll amounts are initialized to each page index. */
+    protected boolean pageScrollsInitialized() {
+        return mPageScrolls != null && mPageScrolls.length == getChildCount();
+    }
+
+    /**
+     * Queues the given callback to be run once {@code mPageScrolls} has been initialized.
+     */
+    public void runOnPageScrollsInitialized(Runnable callback) {
+        mOnPageScrollsInitializedCallbacks.add(callback);
+        if (pageScrollsInitialized()) {
+            onPageScrollsInitialized();
+        }
+    }
+
+    private void onPageScrollsInitialized() {
+        for (Runnable callback : mOnPageScrollsInitializedCallbacks) {
+            callback.run();
+        }
+        mOnPageScrollsInitializedCallbacks.clear();
+    }
+
     @SuppressLint("DrawAllocation")
     @Override
     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
         mIsLayoutValid = true;
         final int childCount = getChildCount();
+        int[] pageScrolls = mPageScrolls;
         boolean pageScrollChanged = false;
-        if (mPageScrolls == null || childCount != mPageScrolls.length) {
-            mPageScrolls = new int[childCount];
+        if (!pageScrollsInitialized()) {
+            pageScrolls = new int[childCount];
             pageScrollChanged = true;
         }
 
@@ -701,10 +727,8 @@
 
         if (DEBUG) Log.d(TAG, "PagedView.onLayout()");
 
-        boolean isScrollChanged = getPageScrolls(mPageScrolls, true, SIMPLE_SCROLL_LOGIC);
-        if (isScrollChanged) {
-            pageScrollChanged = true;
-        }
+        pageScrollChanged |= getPageScrolls(pageScrolls, true, SIMPLE_SCROLL_LOGIC);
+        mPageScrolls = pageScrolls;
 
         final LayoutTransition transition = getLayoutTransition();
         // If the transition is running defer updating max scroll, as some empty pages could
@@ -738,6 +762,7 @@
         if (mScroller.isFinished() && pageScrollChanged) {
             setCurrentPage(getNextPage());
         }
+        onPageScrollsInitialized();
     }
 
     /**
@@ -849,8 +874,10 @@
     @Override
     public void onViewRemoved(View child) {
         super.onViewRemoved(child);
-        mCurrentPage = validateNewPage(mCurrentPage);
-        mCurrentScrollOverPage = mCurrentPage;
+        runOnPageScrollsInitialized(() -> {
+            mCurrentPage = validateNewPage(mCurrentPage);
+            mCurrentScrollOverPage = mCurrentPage;
+        });
         dispatchPageCountChanged();
     }
 
@@ -1153,7 +1180,7 @@
     }
 
     public int getScrollForPage(int index) {
-        if (mPageScrolls == null || index >= mPageScrolls.length || index < 0) {
+        if (!pageScrollsInitialized() || index >= mPageScrolls.length || index < 0) {
             return 0;
         } else {
             return mPageScrolls[index];
@@ -1163,7 +1190,7 @@
     // While layout transitions are occurring, a child's position may stray from its baseline
     // position. This method returns the magnitude of this stray at any given time.
     public int getLayoutTransitionOffsetForPage(int index) {
-        if (mPageScrolls == null || index >= mPageScrolls.length || index < 0) {
+        if (!pageScrollsInitialized() || index >= mPageScrolls.length || index < 0) {
             return 0;
         } else {
             View child = getChildAt(index);