The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2006 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.os; |
| 18 | |
| 19 | import android.util.Config; |
| 20 | import android.util.Printer; |
| 21 | |
| 22 | /** |
| 23 | * Class used to run a message loop for a thread. Threads by default do |
| 24 | * not have a message loop associated with them; to create one, call |
| 25 | * {@link #prepare} in the thread that is to run the loop, and then |
| 26 | * {@link #loop} to have it process messages until the loop is stopped. |
| 27 | * |
| 28 | * <p>Most interaction with a message loop is through the |
| 29 | * {@link Handler} class. |
| 30 | * |
| 31 | * <p>This is a typical example of the implementation of a Looper thread, |
| 32 | * using the separation of {@link #prepare} and {@link #loop} to create an |
| 33 | * initial Handler to communicate with the Looper. |
| 34 | * |
| 35 | * <pre> |
| 36 | * class LooperThread extends Thread { |
| 37 | * public Handler mHandler; |
| 38 | * |
| 39 | * public void run() { |
| 40 | * Looper.prepare(); |
| 41 | * |
| 42 | * mHandler = new Handler() { |
| 43 | * public void handleMessage(Message msg) { |
| 44 | * // process incoming messages here |
| 45 | * } |
| 46 | * }; |
| 47 | * |
| 48 | * Looper.loop(); |
| 49 | * } |
| 50 | * }</pre> |
| 51 | */ |
| 52 | public class Looper { |
| 53 | private static final boolean DEBUG = false; |
| 54 | private static final boolean localLOGV = DEBUG ? Config.LOGD : Config.LOGV; |
| 55 | |
| 56 | // sThreadLocal.get() will return null unless you've called prepare(). |
| 57 | private static final ThreadLocal sThreadLocal = new ThreadLocal(); |
| 58 | |
| 59 | final MessageQueue mQueue; |
| 60 | volatile boolean mRun; |
| 61 | Thread mThread; |
| 62 | private Printer mLogging = null; |
| 63 | private static Looper mMainLooper = null; |
| 64 | |
| 65 | /** Initialize the current thread as a looper. |
| 66 | * This gives you a chance to create handlers that then reference |
| 67 | * this looper, before actually starting the loop. Be sure to call |
| 68 | * {@link #loop()} after calling this method, and end it by calling |
| 69 | * {@link #quit()}. |
| 70 | */ |
| 71 | public static final void prepare() { |
| 72 | if (sThreadLocal.get() != null) { |
| 73 | throw new RuntimeException("Only one Looper may be created per thread"); |
| 74 | } |
| 75 | sThreadLocal.set(new Looper()); |
| 76 | } |
| 77 | |
| 78 | /** Initialize the current thread as a looper, marking it as an application's main |
| 79 | * looper. The main looper for your application is created by the Android environment, |
| 80 | * so you should never need to call this function yourself. |
| 81 | * {@link #prepare()} |
| 82 | */ |
| 83 | |
| 84 | public static final void prepareMainLooper() { |
| 85 | prepare(); |
| 86 | setMainLooper(myLooper()); |
| 87 | if (Process.supportsProcesses()) { |
| 88 | myLooper().mQueue.mQuitAllowed = false; |
| 89 | } |
| 90 | } |
| 91 | |
| 92 | private synchronized static void setMainLooper(Looper looper) { |
| 93 | mMainLooper = looper; |
| 94 | } |
| 95 | |
| 96 | /** Returns the application's main looper, which lives in the main thread of the application. |
| 97 | */ |
| 98 | public synchronized static final Looper getMainLooper() { |
| 99 | return mMainLooper; |
| 100 | } |
| 101 | |
| 102 | /** |
| 103 | * Run the message queue in this thread. Be sure to call |
| 104 | * {@link #quit()} to end the loop. |
| 105 | */ |
| 106 | public static final void loop() { |
| 107 | Looper me = myLooper(); |
| 108 | MessageQueue queue = me.mQueue; |
| 109 | while (true) { |
| 110 | Message msg = queue.next(); // might block |
| 111 | //if (!me.mRun) { |
| 112 | // break; |
| 113 | //} |
| 114 | if (msg != null) { |
| 115 | if (msg.target == null) { |
| 116 | // No target is a magic identifier for the quit message. |
| 117 | return; |
| 118 | } |
| 119 | if (me.mLogging!= null) me.mLogging.println( |
| 120 | ">>>>> Dispatching to " + msg.target + " " |
| 121 | + msg.callback + ": " + msg.what |
| 122 | ); |
| 123 | msg.target.dispatchMessage(msg); |
| 124 | if (me.mLogging!= null) me.mLogging.println( |
| 125 | "<<<<< Finished to " + msg.target + " " |
| 126 | + msg.callback); |
| 127 | msg.recycle(); |
| 128 | } |
| 129 | } |
| 130 | } |
| 131 | |
| 132 | /** |
| 133 | * Return the Looper object associated with the current thread. Returns |
| 134 | * null if the calling thread is not associated with a Looper. |
| 135 | */ |
| 136 | public static final Looper myLooper() { |
| 137 | return (Looper)sThreadLocal.get(); |
| 138 | } |
| 139 | |
| 140 | /** |
| 141 | * Control logging of messages as they are processed by this Looper. If |
| 142 | * enabled, a log message will be written to <var>printer</var> |
| 143 | * at the beginning and ending of each message dispatch, identifying the |
| 144 | * target Handler and message contents. |
| 145 | * |
| 146 | * @param printer A Printer object that will receive log messages, or |
| 147 | * null to disable message logging. |
| 148 | */ |
| 149 | public void setMessageLogging(Printer printer) { |
| 150 | mLogging = printer; |
| 151 | } |
| 152 | |
| 153 | /** |
| 154 | * Return the {@link MessageQueue} object associated with the current |
| 155 | * thread. This must be called from a thread running a Looper, or a |
| 156 | * NullPointerException will be thrown. |
| 157 | */ |
| 158 | public static final MessageQueue myQueue() { |
| 159 | return myLooper().mQueue; |
| 160 | } |
| 161 | |
| 162 | private Looper() { |
| 163 | mQueue = new MessageQueue(); |
| 164 | mRun = true; |
| 165 | mThread = Thread.currentThread(); |
| 166 | } |
| 167 | |
| 168 | public void quit() { |
| 169 | Message msg = Message.obtain(); |
| 170 | // NOTE: By enqueueing directly into the message queue, the |
| 171 | // message is left with a null target. This is how we know it is |
| 172 | // a quit message. |
| 173 | mQueue.enqueueMessage(msg, 0); |
| 174 | } |
| 175 | |
| 176 | /** |
| 177 | * Return the Thread associated with this Looper. |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 178 | */ |
| 179 | public Thread getThread() { |
| 180 | return mThread; |
| 181 | } |
| 182 | |
Jeff Brown | a41ca77 | 2010-08-11 14:46:32 -0700 | [diff] [blame^] | 183 | /** @hide */ |
| 184 | public MessageQueue getQueue() { |
| 185 | return mQueue; |
| 186 | } |
| 187 | |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 188 | public void dump(Printer pw, String prefix) { |
| 189 | pw.println(prefix + this); |
| 190 | pw.println(prefix + "mRun=" + mRun); |
| 191 | pw.println(prefix + "mThread=" + mThread); |
| 192 | pw.println(prefix + "mQueue=" + ((mQueue != null) ? mQueue : "(null")); |
| 193 | if (mQueue != null) { |
| 194 | synchronized (mQueue) { |
| 195 | Message msg = mQueue.mMessages; |
| 196 | int n = 0; |
| 197 | while (msg != null) { |
| 198 | pw.println(prefix + " Message " + n + ": " + msg); |
| 199 | n++; |
| 200 | msg = msg.next; |
| 201 | } |
| 202 | pw.println(prefix + "(Total messages: " + n + ")"); |
| 203 | } |
| 204 | } |
| 205 | } |
| 206 | |
| 207 | public String toString() { |
| 208 | return "Looper{" |
| 209 | + Integer.toHexString(System.identityHashCode(this)) |
| 210 | + "}"; |
| 211 | } |
| 212 | |
| 213 | static class HandlerException extends Exception { |
| 214 | |
| 215 | HandlerException(Message message, Throwable cause) { |
| 216 | super(createMessage(cause), cause); |
| 217 | } |
| 218 | |
| 219 | static String createMessage(Throwable cause) { |
| 220 | String causeMsg = cause.getMessage(); |
| 221 | if (causeMsg == null) { |
| 222 | causeMsg = cause.toString(); |
| 223 | } |
| 224 | return causeMsg; |
| 225 | } |
| 226 | } |
| 227 | } |
| 228 | |