Start listening again after LauncherProvider clears widgets.

After the LauncherProvider resets the database and wipes
out the host info, the Launcher must tell the AppWidgetHost
to listen again.

Originally 87e688d8... in packages/apps/Launcher.

Fixes http://b/2238470

src/com/android/launcher2/Launcher.java

@@ -26,6 +26,7 @@ import android.app.WallpaperInfo;
 import android.app.WallpaperManager;
 import android.content.ActivityNotFoundException;
 import android.content.ComponentName;
+import android.content.ContentResolver;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.content.Intent;
@@ -36,9 +37,11 @@ import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.content.res.Configuration;
 import android.content.res.Resources;
+import android.database.ContentObserver;
 import android.graphics.Bitmap;
 import android.graphics.drawable.Drawable;
 import android.os.Bundle;
+import android.os.Handler;
 import android.os.Parcelable;
 import android.os.RemoteException;
 import android.os.ServiceManager;
@@ -151,6 +154,8 @@ public final class Launcher extends Activity
     private static final Object sLock = new Object();
     private static int sScreen = DEFAULT_SCREEN;
 
+    private final ContentObserver mWidgetObserver = new AppWidgetResetObserver();
+
     private LayoutInflater mInflater;
 
     private DragController mDragController;
@@ -200,7 +205,6 @@ public final class Launcher extends Activity
         mInflater = getLayoutInflater();
 
         mAppWidgetManager = AppWidgetManager.getInstance(this);
-
         mAppWidgetHost = new LauncherAppWidgetHost(this, APPWIDGET_HOST_ID);
         mAppWidgetHost.startListening();
 
@@ -214,6 +218,8 @@ public final class Launcher extends Activity
         setContentView(R.layout.launcher);
         setupViews();
 
+        registerContentObservers();
+
         lockAllApps();
 
         mSavedState = savedInstanceState;
@@ -903,6 +909,8 @@ public final class Launcher extends Activity
 
         unbindDesktopItems();
         AppInfoCache.unbindDrawables();
+
+        getContentResolver().unregisterContentObserver(mWidgetObserver);
     }
 
     @Override
@@ -1269,6 +1277,12 @@ public final class Launcher extends Activity
         startActivityForResult(chooser, REQUEST_PICK_WALLPAPER);
     }
 
+    private void registerContentObservers() {
+        ContentResolver resolver = getContentResolver();
+        resolver.registerContentObserver(LauncherProvider.CONTENT_APPWIDGET_RESET_URI,
+                true, mWidgetObserver);
+    }
+
     @Override
     public boolean dispatchKeyEvent(KeyEvent event) {
         if (event.getAction() == KeyEvent.ACTION_DOWN) {
@@ -1318,6 +1332,13 @@ public final class Launcher extends Activity
         folder.onClose();
     }
 
+    /**
+     * Re-listen when widgets are reset.
+     */
+    private void onAppWidgetReset() {
+        mAppWidgetHost.startListening();
+    }
+
     /**
      * Go through the and disconnect any of the callbacks in the drawables and the views or we
      * leak the previous Home screen on orientation change.
@@ -1763,6 +1784,20 @@ public final class Launcher extends Activity
         }
     }
 
+    /**
+     * Receives notifications whenever the appwidgets are reset.
+     */
+    private class AppWidgetResetObserver extends ContentObserver {
+        public AppWidgetResetObserver() {
+            super(new Handler());
+        }
+
+        @Override
+        public void onChange(boolean selfChange) {
+            onAppWidgetReset();
+        }
+    }
+
     /**
      * Implementation of the method from LauncherModel.Callbacks.
      */