From 7c435f6b441cfc281f77d2467a58a85a4167ffcd Mon Sep 17 00:00:00 2001
From: Fabrice Di Meglio <fdimeglio@google.com>
Date: Tue, 29 Jul 2014 16:02:22 -0700
Subject: [PATCH] Fix bug #16660405 Stability: ISE in Settings: Observer ...
 com.android.settings.SettingsPreferenceFragment$1@3c1d9ecb was not registered

- use a monitor to control registering / unregistering

Change-Id: Id66dd698abf92643c97938e2091c3be38e6b78bd
---
 .../settings/SettingsPreferenceFragment.java    | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/com/android/settings/SettingsPreferenceFragment.java b/src/com/android/settings/SettingsPreferenceFragment.java
index 38344fb8234..f89b72eb29a 100644
--- a/src/com/android/settings/SettingsPreferenceFragment.java
+++ b/src/com/android/settings/SettingsPreferenceFragment.java
@@ -66,6 +66,7 @@ public class SettingsPreferenceFragment extends PreferenceFragment implements Di
     private boolean mPreferenceHighlighted = false;
     private Drawable mHighlightDrawable;
 
+    private Object mRegisterLock = new Object();
     private boolean mIsDataSetObserverRegistered = false;
     private DataSetObserver mDataSetObserver = new DataSetObserver() {
         @Override
@@ -153,16 +154,20 @@ public class SettingsPreferenceFragment extends PreferenceFragment implements Di
     }
 
     public void registerObserverIfNeeded() {
-        if (!mIsDataSetObserverRegistered) {
-            getPreferenceScreen().getRootAdapter().registerDataSetObserver(mDataSetObserver);
-            mIsDataSetObserverRegistered = true;
+        synchronized (mRegisterLock) {
+            if (!mIsDataSetObserverRegistered) {
+                getPreferenceScreen().getRootAdapter().registerDataSetObserver(mDataSetObserver);
+                mIsDataSetObserverRegistered = true;
+            }
         }
     }
 
     public void unregisterObserverIfNeeded() {
-        if (mIsDataSetObserverRegistered) {
-            getPreferenceScreen().getRootAdapter().unregisterDataSetObserver(mDataSetObserver);
-            mIsDataSetObserverRegistered = false;
+        synchronized (mRegisterLock) {
+            if (mIsDataSetObserverRegistered) {
+                getPreferenceScreen().getRootAdapter().unregisterDataSetObserver(mDataSetObserver);
+                mIsDataSetObserverRegistered = false;
+            }
         }
     }