1 /* 2 * Copyright (C) 2013 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 18 package com.android.mail.providers; 19 20 import com.android.mail.ui.FolderController; 21 import com.android.mail.utils.LogTag; 22 import com.android.mail.utils.LogUtils; 23 24 import android.database.DataSetObserver; 25 26 /** 27 * A simple extension of {@link android.database.DataSetObserver} to provide the updated Folder in 28 * {@link #onChanged(Folder)} when the Folder changes. Initializing the object registers with 29 * the observer with the {@link com.android.mail.ui.FolderController} provided. The object will then begin to 30 * receive {@link #onChanged(Folder)} till {@link #unregisterAndDestroy()} is called. 31 * <p> 32 * To implement an {@link FolderObserver}, you need to implement the {@link #onChanged(Folder)} 33 * method. 34 */ 35 public abstract class FolderObserver extends DataSetObserver { 36 /** 37 * The FolderController that the observer is registered with. 38 */ 39 private FolderController mController; 40 41 private static final String LOG_TAG = LogTag.getLogTag(); 42 43 /** 44 * The no-argument constructor leaves the object unusable till 45 * {@link #initialize(FolderController)} is called. 46 */ FolderObserver()47 public FolderObserver () { 48 } 49 50 /** 51 * Initializes an {@link FolderObserver} object that receives a call to 52 * {@link #onChanged(Folder)} when the controller changes the Folder. 53 * 54 * @param controller 55 */ initialize(FolderController controller)56 public Folder initialize(FolderController controller) { 57 if (controller == null) { 58 LogUtils.wtf(LOG_TAG, "FolderObserver initialized with null controller!"); 59 } 60 mController = controller; 61 mController.registerFolderObserver(this); 62 return mController.getFolder(); 63 } 64 65 @Override onChanged()66 public final void onChanged() { 67 if (mController == null) { 68 return; 69 } 70 onChanged(mController.getFolder()); 71 } 72 73 /** 74 * Callback invoked when the Folder object is changed. Since {@link Folder} objects are 75 * immutable, updates can be received on changes to individual settings (sync on/off) 76 * in addition to changes of Folders: alice@example.com -> bob@example.com. 77 * The updated Folder is passed as the argument. 78 * @param newFolder 79 */ onChanged(Folder newFolder)80 public abstract void onChanged(Folder newFolder); 81 82 /** 83 * Return the current folder. 84 * @return 85 */ getFolder()86 public final Folder getFolder() { 87 if (mController == null) { 88 return null; 89 } 90 return mController.getFolder(); 91 } 92 93 /** 94 * Unregisters for Folder changes and makes the object unusable. 95 */ unregisterAndDestroy()96 public void unregisterAndDestroy() { 97 if (mController == null) { 98 return; 99 } 100 mController.unregisterFolderObserver(this); 101 } 102 } 103