| /* |
| * Copyright (C) 2006 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package android.os; |
| |
| import android.util.Log; |
| import android.util.Printer; |
| import android.util.PrefixPrinter; |
| |
| /** |
| * Class used to run a message loop for a thread. Threads by default do |
| * not have a message loop associated with them; to create one, call |
| * {@link #prepare} in the thread that is to run the loop, and then |
| * {@link #loop} to have it process messages until the loop is stopped. |
| * |
| * <p>Most interaction with a message loop is through the |
| * {@link Handler} class. |
| * |
| * <p>This is a typical example of the implementation of a Looper thread, |
| * using the separation of {@link #prepare} and {@link #loop} to create an |
| * initial Handler to communicate with the Looper. |
| * |
| * <pre> |
| * class LooperThread extends Thread { |
| * public Handler mHandler; |
| * |
| * public void run() { |
| * Looper.prepare(); |
| * |
| * mHandler = new Handler() { |
| * public void handleMessage(Message msg) { |
| * // process incoming messages here |
| * } |
| * }; |
| * |
| * Looper.loop(); |
| * } |
| * }</pre> |
| */ |
| public final class Looper { |
| private static final String TAG = "Looper"; |
| |
| // sThreadLocal.get() will return null unless you've called prepare(). |
| static final ThreadLocal<Looper> sThreadLocal = new ThreadLocal<Looper>(); |
| private static Looper sMainLooper; // guarded by Looper.class |
| |
| final MessageQueue mQueue; |
| final Thread mThread; |
| |
| private Printer mLogging; |
| |
| /** Initialize the current thread as a looper. |
| * This gives you a chance to create handlers that then reference |
| * this looper, before actually starting the loop. Be sure to call |
| * {@link #loop()} after calling this method, and end it by calling |
| * {@link #quit()}. |
| */ |
| public static void prepare() { |
| prepare(true); |
| } |
| |
| private static void prepare(boolean quitAllowed) { |
| if (sThreadLocal.get() != null) { |
| throw new RuntimeException("Only one Looper may be created per thread"); |
| } |
| sThreadLocal.set(new Looper(quitAllowed)); |
| } |
| |
| /** |
| * Initialize the current thread as a looper, marking it as an |
| * application's main looper. The main looper for your application |
| * is created by the Android environment, so you should never need |
| * to call this function yourself. See also: {@link #prepare()} |
| */ |
| public static void prepareMainLooper() { |
| prepare(false); |
| synchronized (Looper.class) { |
| if (sMainLooper != null) { |
| throw new IllegalStateException("The main Looper has already been prepared."); |
| } |
| sMainLooper = myLooper(); |
| } |
| } |
| |
| /** Returns the application's main looper, which lives in the main thread of the application. |
| */ |
| public static Looper getMainLooper() { |
| synchronized (Looper.class) { |
| return sMainLooper; |
| } |
| } |
| |
| /** |
| * Run the message queue in this thread. Be sure to call |
| * {@link #quit()} to end the loop. |
| */ |
| public static void loop() { |
| final Looper me = myLooper(); |
| if (me == null) { |
| throw new RuntimeException("No Looper; Looper.prepare() wasn't called on this thread."); |
| } |
| final MessageQueue queue = me.mQueue; |
| |
| // Make sure the identity of this thread is that of the local process, |
| // and keep track of what that identity token actually is. |
| Binder.clearCallingIdentity(); |
| final long ident = Binder.clearCallingIdentity(); |
| |
| for (;;) { |
| Message msg = queue.next(); // might block |
| if (msg == null) { |
| // No message indicates that the message queue is quitting. |
| return; |
| } |
| |
| // This must be in a local variable, in case a UI event sets the logger |
| Printer logging = me.mLogging; |
| if (logging != null) { |
| logging.println(">>>>> Dispatching to " + msg.target + " " + |
| msg.callback + ": " + msg.what); |
| } |
| |
| msg.target.dispatchMessage(msg); |
| |
| if (logging != null) { |
| logging.println("<<<<< Finished to " + msg.target + " " + msg.callback); |
| } |
| |
| // Make sure that during the course of dispatching the |
| // identity of the thread wasn't corrupted. |
| final long newIdent = Binder.clearCallingIdentity(); |
| if (ident != newIdent) { |
| Log.wtf(TAG, "Thread identity changed from 0x" |
| + Long.toHexString(ident) + " to 0x" |
| + Long.toHexString(newIdent) + " while dispatching to " |
| + msg.target.getClass().getName() + " " |
| + msg.callback + " what=" + msg.what); |
| } |
| |
| msg.recycle(); |
| } |
| } |
| |
| /** |
| * Return the Looper object associated with the current thread. Returns |
| * null if the calling thread is not associated with a Looper. |
| */ |
| public static Looper myLooper() { |
| return sThreadLocal.get(); |
| } |
| |
| /** |
| * Control logging of messages as they are processed by this Looper. If |
| * enabled, a log message will be written to <var>printer</var> |
| * at the beginning and ending of each message dispatch, identifying the |
| * target Handler and message contents. |
| * |
| * @param printer A Printer object that will receive log messages, or |
| * null to disable message logging. |
| */ |
| public void setMessageLogging(Printer printer) { |
| mLogging = printer; |
| } |
| |
| /** |
| * Return the {@link MessageQueue} object associated with the current |
| * thread. This must be called from a thread running a Looper, or a |
| * NullPointerException will be thrown. |
| */ |
| public static MessageQueue myQueue() { |
| return myLooper().mQueue; |
| } |
| |
| private Looper(boolean quitAllowed) { |
| mQueue = new MessageQueue(quitAllowed); |
| mThread = Thread.currentThread(); |
| } |
| |
| /** |
| * Returns true if the current thread is this looper's thread. |
| * @hide |
| */ |
| public boolean isCurrentThread() { |
| return Thread.currentThread() == mThread; |
| } |
| |
| /** |
| * Quits the looper. |
| * <p> |
| * Causes the {@link #loop} method to terminate without processing any |
| * more messages in the message queue. |
| * </p><p> |
| * Any attempt to post messages to the queue after the looper is asked to quit will fail. |
| * For example, the {@link Handler#sendMessage(Message)} method will return false. |
| * </p><p class="note"> |
| * Using this method may be unsafe because some messages may not be delivered |
| * before the looper terminates. Consider using {@link #quitSafely} instead to ensure |
| * that all pending work is completed in an orderly manner. |
| * </p> |
| * |
| * @see #quitSafely |
| */ |
| public void quit() { |
| mQueue.quit(false); |
| } |
| |
| /** |
| * Quits the looper safely. |
| * <p> |
| * Causes the {@link #loop} method to terminate as soon as all remaining messages |
| * in the message queue that are already due to be delivered have been handled. |
| * However pending delayed messages with due times in the future will not be |
| * delivered before the loop terminates. |
| * </p><p> |
| * Any attempt to post messages to the queue after the looper is asked to quit will fail. |
| * For example, the {@link Handler#sendMessage(Message)} method will return false. |
| * </p> |
| */ |
| public void quitSafely() { |
| mQueue.quit(true); |
| } |
| |
| /** |
| * Posts a synchronization barrier to the Looper's message queue. |
| * |
| * Message processing occurs as usual until the message queue encounters the |
| * synchronization barrier that has been posted. When the barrier is encountered, |
| * later synchronous messages in the queue are stalled (prevented from being executed) |
| * until the barrier is released by calling {@link #removeSyncBarrier} and specifying |
| * the token that identifies the synchronization barrier. |
| * |
| * This method is used to immediately postpone execution of all subsequently posted |
| * synchronous messages until a condition is met that releases the barrier. |
| * Asynchronous messages (see {@link Message#isAsynchronous} are exempt from the barrier |
| * and continue to be processed as usual. |
| * |
| * This call must be always matched by a call to {@link #removeSyncBarrier} with |
| * the same token to ensure that the message queue resumes normal operation. |
| * Otherwise the application will probably hang! |
| * |
| * @return A token that uniquely identifies the barrier. This token must be |
| * passed to {@link #removeSyncBarrier} to release the barrier. |
| * |
| * @hide |
| */ |
| public int postSyncBarrier() { |
| return mQueue.enqueueSyncBarrier(SystemClock.uptimeMillis()); |
| } |
| |
| |
| /** |
| * Removes a synchronization barrier. |
| * |
| * @param token The synchronization barrier token that was returned by |
| * {@link #postSyncBarrier}. |
| * |
| * @throws IllegalStateException if the barrier was not found. |
| * |
| * @hide |
| */ |
| public void removeSyncBarrier(int token) { |
| mQueue.removeSyncBarrier(token); |
| } |
| |
| /** |
| * Return the Thread associated with this Looper. |
| */ |
| public Thread getThread() { |
| return mThread; |
| } |
| |
| /** @hide */ |
| public MessageQueue getQueue() { |
| return mQueue; |
| } |
| |
| /** |
| * Return whether this looper's thread is currently idle, waiting for new work |
| * to do. This is intrinsically racy, since its state can change before you get |
| * the result back. |
| * @hide |
| */ |
| public boolean isIdling() { |
| return mQueue.isIdling(); |
| } |
| |
| public void dump(Printer pw, String prefix) { |
| pw.println(prefix + toString()); |
| mQueue.dump(pw, prefix + " "); |
| } |
| |
| public String toString() { |
| return "Looper (" + mThread.getName() + ", tid " + mThread.getId() |
| + ") {" + Integer.toHexString(System.identityHashCode(this)) + "}"; |
| } |
| } |