From ae5517e9a4d49c5ff27fc9a96863d31d760fd85d Mon Sep 17 00:00:00 2001
From: Alexandre Elias <aelias@google.com>
Date: Mon, 15 Feb 2021 00:39:19 -0800
Subject: [PATCH] Fix transition animation when going back twice

The logic in ag/5108931 was intended to suppress the next return
animation if it would cross a task boundary, while preserving return
animations in all other cases.  However, it accidentally caused
excessive suppressions in the case of repeated back button presses.  The
reason is that although the sending activity is indeed only topOfTask
when moving forward cross-task, it's *always* topOfTask when pressing
back, so the state of the sending activity doesn't contain sufficient
information to feed this logic.

This patch changes to suppress when the receiving activity is task root,
which is a more direct and reliable signal.  (By definition, the return
transition from an activity will cross a task boundary if and only if
it's the task root.)

Fixes: 177780499
Test: New test in ag/13593522

Change-Id: Ia5751da6122dc1ddb557f45318712185fa0b3df9
---
 core/java/android/app/EnterTransitionCoordinator.java | 6 +++++-
 core/java/android/app/ExitTransitionCoordinator.java  | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/core/java/android/app/EnterTransitionCoordinator.java b/core/java/android/app/EnterTransitionCoordinator.java
index 96751dba04f4d..033cffe38069a 100644
--- a/core/java/android/app/EnterTransitionCoordinator.java
+++ b/core/java/android/app/EnterTransitionCoordinator.java
@@ -52,6 +52,7 @@ class EnterTransitionCoordinator extends ActivityTransitionCoordinator {
 
     private boolean mSharedElementTransitionStarted;
     private Activity mActivity;
+    private boolean mIsTaskRoot;
     private boolean mHasStopped;
     private boolean mIsCanceled;
     private ObjectAnimator mBackgroundAnimator;
@@ -252,7 +253,7 @@ class EnterTransitionCoordinator extends ActivityTransitionCoordinator {
                 cancel();
                 break;
             case MSG_ALLOW_RETURN_TRANSITION:
-                if (!mIsCanceled) {
+                if (!mIsCanceled && !mIsTaskRoot) {
                     mPendingExitNames = mAllSharedElementNames;
                 }
                 break;
@@ -343,6 +344,9 @@ class EnterTransitionCoordinator extends ActivityTransitionCoordinator {
         if (mActivity == null || decorView == null) {
             return;
         }
+
+        mIsTaskRoot = mActivity.isTaskRoot();
+
         if (!isCrossTask()) {
             mActivity.overridePendingTransition(0, 0);
         }
diff --git a/core/java/android/app/ExitTransitionCoordinator.java b/core/java/android/app/ExitTransitionCoordinator.java
index f7097fab6b9ec..cd84e56717533 100644
--- a/core/java/android/app/ExitTransitionCoordinator.java
+++ b/core/java/android/app/ExitTransitionCoordinator.java
@@ -551,7 +551,7 @@ public class ExitTransitionCoordinator extends ActivityTransitionCoordinator {
 
         @Override
         public boolean isReturnTransitionAllowed() {
-            return !mActivity.isTopOfTask();
+            return true;
         }
 
         @Override