commit 1a70a16b64620e416ae8353960c6af6c40274e7a
author Craig Mautner <cmautner@google.com> Sat Sep 13 12:09:31 2014 -0700
committer Craig Mautner <cmautner@google.com> Sat Sep 13 12:09:31 2014 -0700
tree a4f92598264e5824a82b84699f72b56020700d9e
parent df980618a309df46e8569d3b16a6ff4f286e24de

Add null checks for quickly disappearing Displays

If a display is removed right after it is added we will get null
when trying to retrieve it from the DisplayManager. Check for that
null before commiting to using that display.

Fixes bug 17478906.

Change-Id: I89ae8cc7387729d678b9b1ed5b1797a93cdde3f9

services/core/java/com/android/server/am/ActivityStackSupervisor.java

diff --git a/services/core/java/com/android/server/am/ActivityStackSupervisor.java b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
index b8261a4..c48adc4 100644
--- a/services/core/java/com/android/server/am/ActivityStackSupervisor.java
+++ b/services/core/java/com/android/server/am/ActivityStackSupervisor.java
@@ -350,6 +350,9 @@
             for (int displayNdx = displays.length - 1; displayNdx >= 0; --displayNdx) {
                 final int displayId = displays[displayNdx].getDisplayId();
                 ActivityDisplay activityDisplay = new ActivityDisplay(displayId);
+                if (activityDisplay.mDisplay == null) {
+                    throw new IllegalStateException("Default Display does not exist");
+                }
                 mActivityDisplays.put(displayId, activityDisplay);
             }
 
@@ -3261,6 +3264,10 @@
             newDisplay = mActivityDisplays.get(displayId) == null;
             if (newDisplay) {
                 ActivityDisplay activityDisplay = new ActivityDisplay(displayId);
+                if (activityDisplay.mDisplay == null) {
+                    Slog.w(TAG, "Display " + displayId + " gone before initialization complete");
+                    return;
+                }
                 mActivityDisplays.put(displayId, activityDisplay);
             }
         }
@@ -3902,8 +3909,14 @@
         ActivityDisplay() {
         }
 
+        // After instantiation, check that mDisplay is not null before using this. The alternative
+        // is for this to throw an exception if mDisplayManager.getDisplay() returns null.
         ActivityDisplay(int displayId) {
-            init(mDisplayManager.getDisplay(displayId));
+            final Display display = mDisplayManager.getDisplay(displayId);
+            if (display == null) {
+                return;
+            }
+            init(display);
         }
 
         void init(Display display) {