From b69d09ecd948ed9cad861d8176027b9518725e54 Mon Sep 17 00:00:00 2001
From: Trevor Johns <trevorjohns@google.com>
Date: Wed, 31 Oct 2012 16:58:00 -0700
Subject: [PATCH] LunarLander: Fix race condition causing crash on exit

When exiting the LunarLander sample, it was possible for the canvas
to get destroyed before execution was halted.

Added additional synchronization to make sure the current run-state
is accounted for before performing a canvas update.

Also updated deprecated constants in lunar_layout.xml.

Bug: 6164549
Change-Id: I9a710f6b128491f1beece84dd39ab00f4937a4c6
---
 samples/LunarLander/res/layout/lunar_layout.xml  | 16 ++++++++--------
 .../example/android/lunarlander/LunarLander.java |  2 +-
 .../example/android/lunarlander/LunarView.java   | 16 ++++++++++++++--
 3 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/samples/LunarLander/res/layout/lunar_layout.xml b/samples/LunarLander/res/layout/lunar_layout.xml
index f1a899080..bac81881d 100644
--- a/samples/LunarLander/res/layout/lunar_layout.xml
+++ b/samples/LunarLander/res/layout/lunar_layout.xml
@@ -15,21 +15,21 @@
 -->
 
 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    android:layout_width="match_parent"
-    android:layout_height="match_parent">
+    android:layout_width="fill_parent"
+    android:layout_height="fill_parent">
     
     <com.example.android.lunarlander.LunarView
       android:id="@+id/lunar"
-      android:layout_width="match_parent"
-      android:layout_height="match_parent"/>
+      android:layout_width="fill_parent"
+      android:layout_height="fill_parent"/>
     
     <RelativeLayout
-        android:layout_width="match_parent"
-        android:layout_height="match_parent" >
+        android:layout_width="fill_parent"
+        android:layout_height="fill_parent" >
         <TextView
           android:id="@+id/text"
-		  android:text="@string/lunar_layout_text_text"
-		  android:visibility="visible"
+          android:text="@string/lunar_layout_text_text"
+          android:visibility="visible"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:layout_centerInParent="true"
diff --git a/samples/LunarLander/src/com/example/android/lunarlander/LunarLander.java b/samples/LunarLander/src/com/example/android/lunarlander/LunarLander.java
index 15c592334..03faee9f3 100644
--- a/samples/LunarLander/src/com/example/android/lunarlander/LunarLander.java
+++ b/samples/LunarLander/src/com/example/android/lunarlander/LunarLander.java
@@ -149,8 +149,8 @@ public class LunarLander extends Activity {
      */
     @Override
     protected void onPause() {
-        super.onPause();
         mLunarView.getThread().pause(); // pause game when Activity pauses
+        super.onPause();
     }
 
     /**
diff --git a/samples/LunarLander/src/com/example/android/lunarlander/LunarView.java b/samples/LunarLander/src/com/example/android/lunarlander/LunarView.java
index 2a46147ed..81e047084 100644
--- a/samples/LunarLander/src/com/example/android/lunarlander/LunarView.java
+++ b/samples/LunarLander/src/com/example/android/lunarlander/LunarView.java
@@ -196,6 +196,8 @@ class LunarView extends SurfaceView implements SurfaceHolder.Callback {
         /** Indicate whether the surface has been created & is ready to draw */
         private boolean mRun = false;
 
+        private final Object mRunLock = new Object();
+
         /** Scratch rect object. */
         private RectF mScratchRect;
 
@@ -356,7 +358,13 @@ class LunarView extends SurfaceView implements SurfaceHolder.Callback {
                     c = mSurfaceHolder.lockCanvas(null);
                     synchronized (mSurfaceHolder) {
                         if (mMode == STATE_RUNNING) updatePhysics();
-                        doDraw(c);
+                        // Critical section. Do not allow mRun to be set false until
+                        // we are sure all canvas draw operations are complete.
+                        //
+                        // If mRun has been toggled false, inhibit canvas operations.
+                        synchronized (mRunLock) {
+                            if (mRun) doDraw(c);
+                        }
                     }
                 } finally {
                     // do this in a finally so that if an exception is thrown
@@ -427,7 +435,11 @@ class LunarView extends SurfaceView implements SurfaceHolder.Callback {
          * @param b true to run, false to shut down
          */
         public void setRunning(boolean b) {
-            mRun = b;
+            // Do not allow mRun to be modified while any canvas operations
+            // are potentially in-flight. See doDraw().
+            synchronized (mRunLock) {
+                mRun = b;
+            }
         }
 
         /**