From 8698cfbae44dcc6bd61517984e288eda530bb7c5 Mon Sep 17 00:00:00 2001
From: Shan Huang <shanh@google.com>
Date: Mon, 8 Aug 2022 23:38:52 +0000
Subject: [PATCH] Fix back to home animation restarts on a second swipe.

If a second swipe starts before a back to home animation finishes, it's
possible for subsequent MOVE events to start another back animation.
The fix is to only start back animation when the swipe's DOWN event is not
rejected.

Bug: 240109403
Fixes: 240109403
Test: Follow repro steps in 240109403#10 and make sure a second
animation cannot be started.
Test: BackAnimationControllerTest

Change-Id: Id2a5fb00f632fb9be175ef10cad7fea511d09ae0
---
 .../wm/shell/back/BackAnimationController.java    | 15 ++++++++++++++-
 .../shell/back/BackAnimationControllerTest.java   |  7 ++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
index 05fafc54c2737..025fedfc164c0 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
@@ -97,6 +97,8 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
 
     /** Tracks if an uninterruptible transition is in progress */
     private boolean mTransitionInProgress = false;
+    /** Tracks if we should start the back gesture on the next motion move event */
+    private boolean mShouldStartOnNextMoveEvent = false;
     /** @see #setTriggerBack(boolean) */
     private boolean mTriggerBack;
 
@@ -286,12 +288,17 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
         if (mTransitionInProgress) {
             return;
         }
-        if (keyAction == MotionEvent.ACTION_MOVE) {
+        if (keyAction == MotionEvent.ACTION_DOWN) {
             if (!mBackGestureStarted) {
+                mShouldStartOnNextMoveEvent = true;
+            }
+        } else if (keyAction == MotionEvent.ACTION_MOVE) {
+            if (!mBackGestureStarted && mShouldStartOnNextMoveEvent) {
                 // Let the animation initialized here to make sure the onPointerDownOutsideFocus
                 // could be happened when ACTION_DOWN, it may change the current focus that we
                 // would access it when startBackNavigation.
                 onGestureStarted(touchX, touchY);
+                mShouldStartOnNextMoveEvent = false;
             }
             onMove(touchX, touchY, swipeEdge);
         } else if (keyAction == MotionEvent.ACTION_UP || keyAction == MotionEvent.ACTION_CANCEL) {
@@ -425,6 +432,11 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
 
     private void onGestureFinished(boolean fromTouch) {
         ProtoLog.d(WM_SHELL_BACK_PREVIEW, "onGestureFinished() mTriggerBack == %s", mTriggerBack);
+        if (!mBackGestureStarted) {
+            finishAnimation();
+            return;
+        }
+
         if (fromTouch) {
             // Let touch reset the flag otherwise it will start a new back navigation and refresh
             // the info when received a new move event.
@@ -540,6 +552,7 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
         boolean triggerBack = mTriggerBack;
         mBackNavigationInfo = null;
         mTriggerBack = false;
+        mShouldStartOnNextMoveEvent = false;
         if (backNavigationInfo == null) {
             return;
         }
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
index ba81602054a88..365feada9f458 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
@@ -272,9 +272,14 @@ public class BackAnimationControllerTest extends ShellTestCase {
         // the previous transition is finished.
         doMotionEvent(MotionEvent.ACTION_DOWN, 0);
         verifyNoMoreInteractions(mIOnBackInvokedCallback);
+        mController.onBackToLauncherAnimationFinished();
+
+        // Verify that more events from a rejected swipe cannot start animation.
+        doMotionEvent(MotionEvent.ACTION_MOVE, 100);
+        doMotionEvent(MotionEvent.ACTION_UP, 0);
+        verifyNoMoreInteractions(mIOnBackInvokedCallback);
 
         // Verify that we start accepting gestures again once transition finishes.
-        mController.onBackToLauncherAnimationFinished();
         doMotionEvent(MotionEvent.ACTION_DOWN, 0);
         doMotionEvent(MotionEvent.ACTION_MOVE, 100);
         verify(mIOnBackInvokedCallback).onBackStarted();