BackupManager wrapper class improvements

+ Now rechecks the cached IBinder each time the wrapper is used, and if it's
still null (i.e. the BackupManager was constructed before the system service
came up) it's refetched.  This lets even system code cache a single
BackupManager instance and just keep making calls through it without worrying
about interactions with the life cycle of the backup service.

+ Added a static dataChanged(packageName) method as a convenience for code that
needs to indicate that some other package needs a backup pass.  This is useful
even for third party code in the case of multiple packages in a shared-uid
situation.

core/java/android/backup/BackupManager.java

@@ -19,6 +19,7 @@ package android.backup;
 import android.content.Context;
 import android.os.RemoteException;
 import android.os.ServiceManager;
+import android.util.Log;
 
 /**
  * BackupManager is the interface to the system's backup service.
@@ -39,14 +40,17 @@ import android.os.ServiceManager;
  * @hide pending API solidification
  */
 public class BackupManager {
-    private Context mContext;
-    private IBackupManager mService;
+    private static final String TAG = "BackupManager";
 
-    /**
-     * Defined backup transports understood by {@link IBackupManager.selectBackupTransport}.
-     */
-    public static final int TRANSPORT_LOCAL = 1;
-    public static final int TRANSPORT_GOOGLE = 2;
+    private Context mContext;
+    private static IBackupManager sService;
+
+    private static void checkServiceBinder() {
+        if (sService == null) {
+            sService = IBackupManager.Stub.asInterface(
+                    ServiceManager.getService(Context.BACKUP_SERVICE));
+        }
+    }
 
     /**
      * Constructs a BackupManager object through which the application can
@@ -58,8 +62,6 @@ public class BackupManager {
      */
     public BackupManager(Context context) {
         mContext = context;
-        mService = IBackupManager.Stub.asInterface(
-                ServiceManager.getService(Context.BACKUP_SERVICE));
     }
 
     /**
@@ -68,10 +70,31 @@ public class BackupManager {
      * {@link android.app.BackupAgent} subclass will be scheduled when you call this method.
      */
     public void dataChanged() {
-        if (mService != null) {
+        checkServiceBinder();
+        if (sService != null) {
             try {
-                mService.dataChanged(mContext.getPackageName());
+                sService.dataChanged(mContext.getPackageName());
             } catch (RemoteException e) {
+                Log.d(TAG, "dataChanged() couldn't connect");
+            }
+        }
+    }
+
+    /**
+     * Convenience method for callers who need to indicate that some other package
+     * needs a backup pass.  This can be relevant in the case of groups of packages
+     * that share a uid, for example.
+     *
+     * This method requires that the application hold the "android.permission.BACKUP"
+     * permission if the package named in the argument is not the caller's own.
+     */
+    public static void dataChanged(String packageName) {
+        checkServiceBinder();
+        if (sService != null) {
+            try {
+                sService.dataChanged(packageName);
+            } catch (RemoteException e) {
+                Log.d(TAG, "dataChanged(pkg) couldn't connect");
             }
         }
     }
@@ -85,10 +108,12 @@ public class BackupManager {
      */
     public IRestoreSession beginRestoreSession(String transport) {
         IRestoreSession binder = null;
-        if (mService != null) {
+        checkServiceBinder();
+        if (sService != null) {
             try {
-                binder = mService.beginRestoreSession(transport);
+                binder = sService.beginRestoreSession(transport);
             } catch (RemoteException e) {
+                Log.d(TAG, "beginRestoreSession() couldn't connect");
             }
         }
         return binder;

tests/backup/src/com/android/backuptest/BackupTestActivity.java

@@ -52,6 +52,8 @@ public class BackupTestActivity extends ListActivity
     static final String PREF_KEY = "pref";
     static final String FILE_NAME = "file.txt";
 
+    BackupManager sBm = new BackupManager(this);
+
     Test[] mTests = new Test[] {
         new Test("Show File") {
             void run() {
@@ -85,8 +87,7 @@ public class BackupTestActivity extends ListActivity
                         output.close();
                     }
                 }
-                BackupManager bm = new BackupManager(BackupTestActivity.this);
-                bm.dataChanged();
+                sBm.dataChanged();
             }
         },
         new Test("Clear File") {
@@ -100,14 +101,12 @@ public class BackupTestActivity extends ListActivity
                         output.close();
                     }
                 }
-                BackupManager bm = new BackupManager(BackupTestActivity.this);
-                bm.dataChanged();
+                sBm.dataChanged();
             }
         },
         new Test("Poke") {
             void run() {
-                BackupManager bm = new BackupManager(BackupTestActivity.this);
-                bm.dataChanged();
+                sBm.dataChanged();
             }
         },
         new Test("Show Shared Pref") {
@@ -126,8 +125,7 @@ public class BackupTestActivity extends ListActivity
                 SharedPreferences.Editor editor = prefs.edit();
                 editor.putInt(PREF_KEY, val+1);
                 editor.commit();
-                BackupManager bm = new BackupManager(BackupTestActivity.this);
-                bm.dataChanged();
+                sBm.dataChanged();
             }
         },
         new Test("Backup Helpers") {