From 1f544beb7a5bfa7ae34aa86ecf939254ad18d47a Mon Sep 17 00:00:00 2001
From: Wale Ogunwale <ogunwale@google.com>
Date: Thu, 17 Dec 2015 10:27:23 -0800
Subject: [PATCH] Use accessor methods to get/set visibleBehindActivity

The accessor methods have protection against the stack been
in a detached state. Reading the field directly can lead to
an NPE when the stack is detached.

Bug: 26209403
Change-Id: I66fc1871ea96504cf1bcbc72cae9b564d6527bce
---
 .../java/com/android/server/am/ActivityStack.java     | 11 +++++------
 .../android/server/am/ActivityStackSupervisor.java    |  2 +-
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/services/core/java/com/android/server/am/ActivityStack.java b/services/core/java/com/android/server/am/ActivityStack.java
index bfd17b2e1bf96..ada71f670e783 100644
--- a/services/core/java/com/android/server/am/ActivityStack.java
+++ b/services/core/java/com/android/server/am/ActivityStack.java
@@ -813,10 +813,9 @@ final class ActivityStack {
 
         if (hasVisibleBehindActivity()) {
             // Stop visible behind activity before going to sleep.
-            final ActivityRecord r = mActivityContainer.mActivityDisplay.mVisibleBehindActivity;
+            final ActivityRecord r = getVisibleBehindActivity();
             mStackSupervisor.mStoppingActivities.add(r);
-            if (DEBUG_STATES) Slog.v(TAG_STATES,
-                    "Sleep still waiting to stop visible behind " + r);
+            if (DEBUG_STATES) Slog.v(TAG_STATES, "Sleep still waiting to stop visible behind " + r);
             return true;
         }
 
@@ -1053,7 +1052,7 @@ final class ActivityStack {
             mHandler.removeMessages(STOP_TIMEOUT_MSG, r);
             r.stopped = true;
             r.state = ActivityState.STOPPED;
-            if (mActivityContainer.mActivityDisplay.mVisibleBehindActivity == r) {
+            if (getVisibleBehindActivity() == r) {
                 mStackSupervisor.requestVisibleBehindLocked(r, false);
             }
             if (r.finishing) {
@@ -1214,9 +1213,9 @@ final class ActivityStack {
 
         next.returningOptions = null;
 
-        if (mActivityContainer.mActivityDisplay.mVisibleBehindActivity == next) {
+        if (getVisibleBehindActivity() == next) {
             // When resuming an activity, require it to call requestVisibleBehind() again.
-            mActivityContainer.mActivityDisplay.setVisibleBehindActivity(null);
+            setVisibleBehindActivity(null);
         }
     }
 
diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index 80d531e71f3ec..271a9437b5546 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -5170,7 +5170,7 @@ public final class ActivityStackSupervisor implements DisplayListener {
 
         /** All of the stacks on this display. Order matters, topmost stack is in front of all other
          * stacks, bottommost behind. Accessed directly by ActivityManager package classes */
-        final ArrayList<ActivityStack> mStacks = new ArrayList<ActivityStack>();
+        final ArrayList<ActivityStack> mStacks = new ArrayList<>();
 
         ActivityRecord mVisibleBehindActivity;