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 /** 22 * Defines the calling interface that {@link BackupAgentHelper} uses 23 * when dispatching backup and restore operations to the installed helpers. 24 * Applications can define and install their own helpers as well as using those 25 * provided as part of the Android framework. 26 * <p> 27 * Although multiple helper objects may be installed simultaneously, each helper 28 * is responsible only for handling its own data, and will not see entities 29 * created by other components within the backup system. Invocations of multiple 30 * helpers are performed sequentially by the {@link BackupAgentHelper}, with each 31 * helper given a chance to access its own saved state from within the state record 32 * produced during the previous backup operation. 33 * 34 * @see BackupAgentHelper 35 * @see FileBackupHelper 36 * @see SharedPreferencesBackupHelper 37 */ 38 public interface BackupHelper { 39 /** 40 * Based on <code>oldState</code>, determine which of the files from the 41 * application's data directory need to be backed up, write them to 42 * <code>data</code>, and fill in <code>newState</code> with the state as it 43 * exists now. 44 * <p> 45 * Implementing this method is much like implementing 46 * {@link BackupAgent#onBackup(ParcelFileDescriptor, BackupDataOutput, ParcelFileDescriptor) 47 * onBackup()} — the method parameters are the same. When this method is invoked the 48 * {@code oldState} descriptor points to the beginning of the state data 49 * written during this helper's previous backup operation, and the {@code newState} 50 * descriptor points to the file location at which the helper should write its 51 * new state after performing the backup operation. 52 * <p class="note"> 53 * <strong>Note:</strong> The helper should not close or seek either the {@code oldState} or 54 * the {@code newState} file descriptors.</p> 55 * 56 * @param oldState An open, read-only {@link android.os.ParcelFileDescriptor} pointing to the 57 * last backup state provided by the application. May be 58 * <code>null</code>, in which case no prior state is being 59 * provided and the application should perform a full backup. 60 * @param data An open, read/write {@link BackupDataOutput} 61 * pointing to the backup data destination. 62 * Typically the application will use backup helper classes to 63 * write to this file. 64 * @param newState An open, read/write {@link android.os.ParcelFileDescriptor} pointing to an 65 * empty file. The application should record the final backup 66 * state here after writing the requested data to the <code>data</code> 67 * output stream. 68 */ 69 public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data, 70 ParcelFileDescriptor newState); 71 72 /** 73 * Called by {@link android.app.backup.BackupAgentHelper BackupAgentHelper} 74 * to restore a single entity from the restore data set. This method will be 75 * called for each entity in the data set that belongs to this handler. 76 * <p class="note"> 77 * <strong>Note:</strong> Do not close the <code>data</code> stream. Do not read more than 78 * {@link android.app.backup.BackupDataInputStream#size() size()} bytes from 79 * <code>data</code>.</p> 80 * 81 * @param data An open {@link BackupDataInputStream} from which the backup data can be read. 82 */ 83 public void restoreEntity(BackupDataInputStream data); 84 85 /** 86 * Called by {@link android.app.backup.BackupAgentHelper BackupAgentHelper} 87 * after a restore operation to write the backup state file corresponding to 88 * the data as processed by the helper. The data written here will be 89 * available to the helper during the next call to its 90 * {@link #performBackup(ParcelFileDescriptor, BackupDataOutput, ParcelFileDescriptor) 91 * performBackup()} method. 92 * <p> 93 * This method will be called even if the handler's 94 * {@link #restoreEntity(BackupDataInputStream) restoreEntity()} method was never invoked during 95 * the restore operation. 96 * <p class="note"> 97 * <strong>Note:</strong> The helper should not close or seek the {@code newState} 98 * file descriptor.</p> 99 * 100 * @param newState A {@link android.os.ParcelFileDescriptor} to which the new state will be 101 * written. 102 */ 103 public void writeNewStateDescription(ParcelFileDescriptor newState); 104 } 105 106
