1 /* 2 * Copyright (C) 2012 Google Inc. 3 * Licensed to The Android Open Source Project. 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package com.android.mail.providers; 19 20 import android.database.DataSetObserver; 21 22 import com.android.mail.ui.RecentFolderController; 23 import com.android.mail.ui.RecentFolderList; 24 import com.android.mail.utils.LogTag; 25 import com.android.mail.utils.LogUtils; 26 27 /** 28 * A simple extension of {@link DataSetObserver} to provide the updated recent folders 29 * {@link #onChanged()} when they change. Initializing the object registers with 30 * the observer with the {@link RecentFolderObserver} provided. The object will then begin to 31 * receive {@link #onChanged()} till {@link #unregisterAndDestroy()} is called. 32 * The {@link RecentFolderList} returned in {@link #initialize(RecentFolderController)} is updated 33 * directly, no new object is created when the recent folder list is updated. 34 * <p> 35 * To implement an {@link RecentFolderObserver}, you need to implement the 36 * {@link #onChanged()} method. 37 */ 38 public abstract class RecentFolderObserver extends DataSetObserver { 39 /** 40 * The RecentFolderController that the observer is registered with. 41 */ 42 private RecentFolderController mController; 43 44 private static final String LOG_TAG = LogTag.getLogTag(); 45 46 /** 47 * The no-argument constructor leaves the object unusable till 48 * {@link #initialize(RecentFolderController)} is called. 49 */ RecentFolderObserver()50 public RecentFolderObserver () { 51 } 52 53 /** 54 * Initializes an {@link RecentFolderObserver} object that receives a call to 55 * {@link #onChanged()} when the controller changes the recent folder. 56 * 57 * @param controller 58 */ initialize(RecentFolderController controller)59 public RecentFolderList initialize(RecentFolderController controller) { 60 if (controller == null) { 61 LogUtils.wtf(LOG_TAG, "RecentFolderObserver initialized with null controller!"); 62 } 63 mController = controller; 64 mController.registerRecentFolderObserver(this); 65 return mController.getRecentFolders(); 66 } 67 68 @Override onChanged()69 public abstract void onChanged(); 70 71 /** 72 * Return the most current recent folder. 73 * @return 74 */ getRecentFolders()75 public final RecentFolderList getRecentFolders() { 76 if (mController == null) { 77 return null; 78 } 79 return mController.getRecentFolders(); 80 } 81 82 /** 83 * Unregisters for recent folder changes and makes the object unusable. 84 */ unregisterAndDestroy()85 public void unregisterAndDestroy() { 86 if (mController == null) { 87 return; 88 } 89 mController.unregisterRecentFolderObserver(this); 90 } 91 }