From 9a2454c59578c50057440134f1f525650985f07f Mon Sep 17 00:00:00 2001
From: Riddle Hsu <riddlehsu@google.com>
Date: Fri, 2 Jul 2021 14:06:22 +0800
Subject: [PATCH] Fix NPE caused by config change on a destroyed activity

The config callback from view root may not know the state
of activity. That may trigger a stale callback, so
 - Restore the null check when getting mSizeConfigurations.
 - Clear the callback if the activity will be removed.

Bug: 192603207
Test: ActivityLifecycleTopResumedStateTests
Change-Id: I17ea8fc2ba994f630d5ad7baa3de298d90a32827
---
 core/java/android/app/ActivityThread.java | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/core/java/android/app/ActivityThread.java b/core/java/android/app/ActivityThread.java
index 6505adccb46f7..7e0ccaef4f6b7 100644
--- a/core/java/android/app/ActivityThread.java
+++ b/core/java/android/app/ActivityThread.java
@@ -5430,6 +5430,12 @@ public final class ActivityThread extends ClientTransactionHandler
                     // behave properly when activity is relaunching.
                     r.window.clearContentView();
                 } else {
+                    final ViewRootImpl viewRoot = v.getViewRootImpl();
+                    if (viewRoot != null) {
+                        // Clear the callback to avoid the destroyed activity from receiving
+                        // configuration changes that are no longer effective.
+                        viewRoot.setActivityConfigCallback(null);
+                    }
                     wm.removeViewImmediate(v);
                 }
             }
@@ -5834,10 +5840,9 @@ public final class ActivityThread extends ClientTransactionHandler
 
         final boolean movedToDifferentDisplay = isDifferentDisplay(activity.getDisplayId(),
                 displayId);
-        final SizeConfigurationBuckets buckets = getActivityClient(activityToken)
-                .mSizeConfigurations;
+        final ActivityClientRecord r = mActivities.get(activityToken);
         final int diff = diffPublicWithSizeBuckets(activity.mCurrentConfig,
-                newConfig, buckets);
+                newConfig, r != null ? r.mSizeConfigurations : null);
         final boolean hasPublicConfigChange = diff != 0;
         // TODO(b/173090263): Use diff instead after the improvement of AssetManager and
         // ResourcesImpl constructions.