/* * Copyright (C) 2009 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.app.backup; import android.app.QueuedWork; import android.content.Context; import android.content.SharedPreferences; import android.os.ParcelFileDescriptor; import android.util.Log; import java.io.File; /** * A helper class that can be used in conjunction with * {@link android.app.backup.BackupAgentHelper} to manage the backup of * {@link android.content.SharedPreferences}. Whenever a backup is performed, it * will back up all named shared preferences that have changed since the last * backup operation. *

* To use this class, the application's backup agent class should extend * {@link android.app.backup.BackupAgentHelper}. Then, in the agent's * {@link BackupAgent#onCreate()} method, an instance of this class should be * allocated and installed as a backup/restore handler within the BackupAgentHelper * framework. For example, an agent supporting backup and restore for * an application with two groups of {@link android.content.SharedPreferences} * data might look something like this: *

 * import android.app.backup.BackupAgentHelper;
 * import android.app.backup.SharedPreferencesBackupHelper;
 *
 * public class MyBackupAgent extends BackupAgentHelper {
 *     // The names of the SharedPreferences groups that the application maintains.  These
 *     // are the same strings that are passed to {@link Context#getSharedPreferences(String, int)}.
 *     static final String PREFS_DISPLAY = "displayprefs";
 *     static final String PREFS_SCORES = "highscores";
 *
 *     // An arbitrary string used within the BackupAgentHelper implementation to
 *     // identify the SharedPreferenceBackupHelper's data.
 *     static final String MY_PREFS_BACKUP_KEY = "myprefs";
 *
 *     // Simply allocate a helper and install it
 *     void onCreate() {
 *         SharedPreferencesBackupHelper helper =
 *                 new SharedPreferencesBackupHelper(this, PREFS_DISPLAY, PREFS_SCORES);
 *         addHelper(MY_PREFS_BACKUP_KEY, helper);
 *     }
 * }
*

* No further implementation is needed; the {@link BackupAgentHelper} mechanism automatically * dispatches the * {@link BackupAgent#onBackup(android.os.ParcelFileDescriptor, BackupDataOutput, android.os.ParcelFileDescriptor) BackupAgent.onBackup()} * and * {@link BackupAgent#onRestore(BackupDataInput, int, android.os.ParcelFileDescriptor) BackupAgent.onRestore()} * callbacks to the SharedPreferencesBackupHelper as appropriate. */ public class SharedPreferencesBackupHelper extends FileBackupHelperBase implements BackupHelper { private static final String TAG = "SharedPreferencesBackupHelper"; private static final boolean DEBUG = false; private Context mContext; private String[] mPrefGroups; /** * Construct a helper for backing up and restoring the * {@link android.content.SharedPreferences} under the given names. * * @param context The application {@link android.content.Context} * @param prefGroups The names of each {@link android.content.SharedPreferences} file to * back up */ public SharedPreferencesBackupHelper(Context context, String... prefGroups) { super(context); mContext = context; mPrefGroups = prefGroups; } /** * Backs up the configured {@link android.content.SharedPreferences} groups. */ public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data, ParcelFileDescriptor newState) { Context context = mContext; // If a SharedPreference has an outstanding write in flight, // wait for it to finish flushing to disk. QueuedWork.waitToFinish(); // make filenames for the prefGroups String[] prefGroups = mPrefGroups; final int N = prefGroups.length; String[] files = new String[N]; for (int i=0; i