1 /* 2 * Copyright (C) 2007 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.database; 18 19 import android.os.Handler; 20 21 /** 22 * Receives call backs for changes to content. Must be implemented by objects which are added 23 * to a {@link ContentObservable}. 24 */ 25 public abstract class ContentObserver { 26 27 private Transport mTransport; 28 29 // Protects mTransport 30 private Object lock = new Object(); 31 32 /* package */ Handler mHandler; 33 34 private final class NotificationRunnable implements Runnable { 35 36 private boolean mSelf; 37 NotificationRunnable(boolean self)38 public NotificationRunnable(boolean self) { 39 mSelf = self; 40 } 41 run()42 public void run() { 43 ContentObserver.this.onChange(mSelf); 44 } 45 } 46 47 private static final class Transport extends IContentObserver.Stub { 48 ContentObserver mContentObserver; 49 Transport(ContentObserver contentObserver)50 public Transport(ContentObserver contentObserver) { 51 mContentObserver = contentObserver; 52 } 53 deliverSelfNotifications()54 public boolean deliverSelfNotifications() { 55 ContentObserver contentObserver = mContentObserver; 56 if (contentObserver != null) { 57 return contentObserver.deliverSelfNotifications(); 58 } 59 return false; 60 } 61 onChange(boolean selfChange)62 public void onChange(boolean selfChange) { 63 ContentObserver contentObserver = mContentObserver; 64 if (contentObserver != null) { 65 contentObserver.dispatchChange(selfChange); 66 } 67 } 68 releaseContentObserver()69 public void releaseContentObserver() { 70 mContentObserver = null; 71 } 72 } 73 74 /** 75 * onChange() will happen on the provider Handler. 76 * 77 * @param handler The handler to run {@link #onChange} on. 78 */ ContentObserver(Handler handler)79 public ContentObserver(Handler handler) { 80 mHandler = handler; 81 } 82 83 /** 84 * Gets access to the binder transport object. Not for public consumption. 85 * 86 * {@hide} 87 */ getContentObserver()88 public IContentObserver getContentObserver() { 89 synchronized(lock) { 90 if (mTransport == null) { 91 mTransport = new Transport(this); 92 } 93 return mTransport; 94 } 95 } 96 97 /** 98 * Gets access to the binder transport object, and unlinks the transport object 99 * from the ContentObserver. Not for public consumption. 100 * 101 * {@hide} 102 */ releaseContentObserver()103 public IContentObserver releaseContentObserver() { 104 synchronized(lock) { 105 Transport oldTransport = mTransport; 106 if (oldTransport != null) { 107 oldTransport.releaseContentObserver(); 108 mTransport = null; 109 } 110 return oldTransport; 111 } 112 } 113 114 /** 115 * Returns true if this observer is interested in notifications for changes 116 * made through the cursor the observer is registered with. 117 */ deliverSelfNotifications()118 public boolean deliverSelfNotifications() { 119 return false; 120 } 121 122 /** 123 * This method is called when a change occurs to the cursor that 124 * is being observed. 125 * 126 * @param selfChange true if the update was caused by a call to <code>commit</code> on the 127 * cursor that is being observed. 128 */ onChange(boolean selfChange)129 public void onChange(boolean selfChange) {} 130 dispatchChange(boolean selfChange)131 public final void dispatchChange(boolean selfChange) { 132 if (mHandler == null) { 133 onChange(selfChange); 134 } else { 135 mHandler.post(new NotificationRunnable(selfChange)); 136 } 137 } 138 } 139