Fix 3106227: use WeakReferences for receivers in DigitalClock class

This works around a bug in the framework where LockScreen wouldn't
get GC'd under certain circumstances which would lead to an OOM
crash.  It now uses WeakReferences for observers inside the
DigitalClock container class and unregisters them if the containing
DigitalClock goes away.

Also removed mLive variable which was unused and could potentially
leak the receivers.

Left mAttached for debugging so we can use it to determine if the
calls to onAttachToWindow() and onDetachFromWindow() are grossly
unbalanced which may be the root cause of the original problem.

Have cleanUp() explicitly clear unused references to make
tracing through hprof references easier.

Change-Id: I99a7e0c356001b05eab5aa729564553666febfea

1 files changed, 63 insertions, 40 deletions

diff --git a/core/java/com/android/internal/widget/DigitalClock.java b/core/java/com/android/internal/widget/DigitalClock.java
index fa47ff6..303a1bf 100644
--- a/core/java/com/android/internal/widget/DigitalClock.java
+++ b/core/java/com/android/internal/widget/DigitalClock.java
@@ -22,7 +22,6 @@ import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
-import android.content.res.Resources;
 import android.database.ContentObserver;
 import android.graphics.Typeface;
 import android.os.Handler;
@@ -33,6 +32,7 @@ import android.view.View;
 import android.widget.LinearLayout;
 import android.widget.TextView;
 
+import java.lang.ref.WeakReference;
 import java.text.DateFormatSymbols;
 import java.util.Calendar;
 
@@ -49,26 +49,41 @@ public class DigitalClock extends LinearLayout {
     private TextView mTimeDisplay;
     private AmPm mAmPm;
     private ContentObserver mFormatChangeObserver;
-    private boolean mLive = true;
-    private boolean mAttached;
+    private int mAttached = 0; // for debugging - tells us whether attach/detach is unbalanced
 
     /* called by system on minute ticks */
     private final Handler mHandler = new Handler();
-    private final BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
-            @Override
-            public void onReceive(Context context, Intent intent) {
-                if (mLive && intent.getAction().equals(
-                            Intent.ACTION_TIMEZONE_CHANGED)) {
-                    mCalendar = Calendar.getInstance();
-                }
-                // Post a runnable to avoid blocking the broadcast.
-                mHandler.post(new Runnable() {
-                        public void run() {
-                            updateTime();
+    private BroadcastReceiver mIntentReceiver;
+
+    private static class TimeChangedReceiver extends BroadcastReceiver {
+        private WeakReference<DigitalClock> mClock;
+        private Context mContext;
+
+        public TimeChangedReceiver(DigitalClock clock) {
+            mClock = new WeakReference<DigitalClock>(clock);
+            mContext = clock.getContext();
+        }
+
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            // Post a runnable to avoid blocking the broadcast.
+            final boolean timezoneChanged =
+                    intent.getAction().equals(Intent.ACTION_TIMEZONE_CHANGED);
+            final DigitalClock clock = mClock.get();
+            if (clock != null) {
+                clock.mHandler.post(new Runnable() {
+                    public void run() {
+                        if (timezoneChanged) {
+                            clock.mCalendar = Calendar.getInstance();
                         }
+                        clock.updateTime();
+                    }
                 });
+            } else {
+                mContext.unregisterReceiver(this);
             }
-        };
+        }
+    };
 
     static class AmPm {
         private TextView mAmPm;
@@ -94,14 +109,23 @@ public class DigitalClock extends LinearLayout {
         }
     }
 
-    private class FormatChangeObserver extends ContentObserver {
-        public FormatChangeObserver() {
+    private static class FormatChangeObserver extends ContentObserver {
+        private WeakReference<DigitalClock> mClock;
+        private Context mContext;
+        public FormatChangeObserver(DigitalClock clock) {
             super(new Handler());
+            mClock = new WeakReference<DigitalClock>(clock);
+            mContext = clock.getContext();
         }
         @Override
         public void onChange(boolean selfChange) {
-            setDateFormat();
-            updateTime();
+            DigitalClock digitalClock = mClock.get();
+            if (digitalClock != null) {
+                digitalClock.setDateFormat();
+                digitalClock.updateTime();
+            } else {
+                mContext.getContentResolver().unregisterContentObserver(this);
+            }
         }
     }
 
@@ -129,11 +153,11 @@ public class DigitalClock extends LinearLayout {
     protected void onAttachedToWindow() {
         super.onAttachedToWindow();
 
-        if (mAttached) return;
-        mAttached = true;
+        mAttached++;
 
-        if (mLive) {
-            /* monitor time ticks, time changed, timezone */
+        /* monitor time ticks, time changed, timezone */
+        if (mIntentReceiver == null) {
+            mIntentReceiver = new TimeChangedReceiver(this);
             IntentFilter filter = new IntentFilter();
             filter.addAction(Intent.ACTION_TIME_TICK);
             filter.addAction(Intent.ACTION_TIME_CHANGED);
@@ -142,9 +166,11 @@ public class DigitalClock extends LinearLayout {
         }
 
         /* monitor 12/24-hour display preference */
-        mFormatChangeObserver = new FormatChangeObserver();
-        mContext.getContentResolver().registerContentObserver(
-                Settings.System.CONTENT_URI, true, mFormatChangeObserver);
+        if (mFormatChangeObserver == null) {
+            mFormatChangeObserver = new FormatChangeObserver(this);
+            mContext.getContentResolver().registerContentObserver(
+                    Settings.System.CONTENT_URI, true, mFormatChangeObserver);
+        }
 
         updateTime();
     }
@@ -153,16 +179,19 @@ public class DigitalClock extends LinearLayout {
     protected void onDetachedFromWindow() {
         super.onDetachedFromWindow();
 
-        if (!mAttached) return;
-        mAttached = false;
+        mAttached--;
 
-        if (mLive) {
+        if (mIntentReceiver != null) {
             mContext.unregisterReceiver(mIntentReceiver);
         }
-        mContext.getContentResolver().unregisterContentObserver(
-                mFormatChangeObserver);
-    }
+        if (mFormatChangeObserver != null) {
+            mContext.getContentResolver().unregisterContentObserver(
+                    mFormatChangeObserver);
+        }
 
+        mFormatChangeObserver = null;
+        mIntentReceiver = null;
+    }
 
     void updateTime(Calendar c) {
         mCalendar = c;
@@ -170,9 +199,7 @@ public class DigitalClock extends LinearLayout {
     }
 
     private void updateTime() {
-        if (mLive) {
-            mCalendar.setTimeInMillis(System.currentTimeMillis());
-        }
+        mCalendar.setTimeInMillis(System.currentTimeMillis());
 
         CharSequence newTime = DateFormat.format(mFormat, mCalendar);
         mTimeDisplay.setText(newTime);
@@ -180,12 +207,8 @@ public class DigitalClock extends LinearLayout {
     }
 
     private void setDateFormat() {
-        mFormat = android.text.format.DateFormat.is24HourFormat(getContext()) 
+        mFormat = android.text.format.DateFormat.is24HourFormat(getContext())
             ? M24 : M12;
         mAmPm.setShowAmPm(mFormat.equals(M12));
     }
-
-    void setLive(boolean live) {
-        mLive = live;
-    }
 }