1 /*
2  * Copyright (C) 2009 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package android.app.backup;
18 
19 import android.os.ParcelFileDescriptor;
20 
21 import java.io.IOException;
22 
23 /**
24  * A convenient {@link BackupAgent} wrapper class that automatically manages
25  * heterogeneous data sets within the backup data, each identified by a unique
26  * key prefix.  When processing a backup or restore operation, the BackupAgentHelper
27  * dispatches to one or more installed {@link BackupHelper} objects, each
28  * of which is responsible for a defined subset of the data being processed.
29  * <p>
30  * An application will typically extend this class in its own
31  * backup agent. Then, within the agent's {@link BackupAgent#onCreate() onCreate()}
32  * method, it will call {@link #addHelper(String, BackupHelper) addHelper()} one or more times to
33  * install the handlers for each kind of data it wishes to manage within its backups.
34  * <p>
35  * The Android framework currently provides two predefined {@link BackupHelper} classes:</p>
36  * <ul><li>{@link FileBackupHelper} - Manages the backup and restore of entire files
37  * within an application's data directory hierarchy.</li>
38  * <li>{@link SharedPreferencesBackupHelper} - Manages the backup and restore of an
39  * application's {@link android.content.SharedPreferences} data.</li></ul>
40  * <p>
41  * An application can also implement its own helper classes to work within the
42  * {@link BackupAgentHelper} framework.  See the {@link BackupHelper} interface
43  * documentation for details.
44  *
45  * <div class="special reference">
46  * <h3>Developer Guides</h3>
47  * <p>For more information about using BackupAgentHelper, read the
48  * <a href="{@docRoot}guide/topics/data/backup.html">Data Backup</a> developer guide.</p>
49  * </div>
50  *
51  * @see BackupHelper
52  * @see FileBackupHelper
53  * @see SharedPreferencesBackupHelper
54  */
55 public class BackupAgentHelper extends BackupAgent {
56     static final String TAG = "BackupAgentHelper";
57 
58     BackupHelperDispatcher mDispatcher = new BackupHelperDispatcher();
59 
60     /**
61      * Run the backup process on each of the configured handlers.
62      */
63     @Override
onBackup(ParcelFileDescriptor oldState, BackupDataOutput data, ParcelFileDescriptor newState)64     public void onBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
65              ParcelFileDescriptor newState) throws IOException {
66         mDispatcher.performBackup(oldState, data, newState);
67     }
68 
69     /**
70      * Run the restore process on each of the configured handlers.
71      */
72     @Override
onRestore(BackupDataInput data, int appVersionCode, ParcelFileDescriptor newState)73     public void onRestore(BackupDataInput data, int appVersionCode, ParcelFileDescriptor newState)
74             throws IOException {
75         mDispatcher.performRestore(data, appVersionCode, newState);
76     }
77 
78     /** @hide */
getDispatcher()79     public BackupHelperDispatcher getDispatcher() {
80         return mDispatcher;
81     }
82 
83     /**
84      * Add a helper for a given data subset to the agent's configuration.  Each helper
85      * must have a prefix string that is unique within this backup agent's set of
86      * helpers.
87      *
88      * @param keyPrefix A string used to disambiguate the various helpers within this agent
89      * @param helper A backup/restore helper object to be invoked during backup and restore
90      *    operations.
91      */
addHelper(String keyPrefix, BackupHelper helper)92     public void addHelper(String keyPrefix, BackupHelper helper) {
93         mDispatcher.addHelper(keyPrefix, helper);
94     }
95 }
96 
97 
98