源码分析/** 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;/*** Handy class for starting a new thread that has a looper. The looper can then be* used to create handler classes. Note that start() must still be called.*/public class HandlerThread extends Thread {int mPriority; int mTid = -1;Looper mLooper; public HandlerThread(String name) {super(name);mPriority = Process.THREAD_PRIORITY_DEFAULT;}/** * Constructs a HandlerThread. * @param name* @param priority The priority to run the thread at. The value supplied must be from * {@link android.os.Process} and not from java.lang.Thread. */public HandlerThread(String name, int priority) {super(name);mPriority = priority;}/** * Call back method that can be explicitly overridden if needed to execute some * setup before Looper loops. */protected void onLooperPrepared() {}@Overridepublic void run() {mTid = Process.myTid();Looper.prepare(); synchronized (this) {mLooper = Looper.myLooper();notifyAll();}Process.setThreadPriority(mPriority);onLooperPrepared();Looper.loop();mTid = -1;}/** * This method returns the Looper associated with this thread. If this thread not been started * or for any reason is isAlive() returns false, this method will return null. If this thread * has been started, this method will block until the looper has been initialized. * @return The looper. */public Looper getLooper() {if (!isAlive()) {return null;}// If the thread has been started, wait until the looper has been created.synchronized (this) {while (isAlive() && mLooper == null) {try {wait();} catch (InterruptedException e) {}}}return mLooper;}/** * Quits the handler thread's looper. *

* Causes the handler thread's looper to terminate without processing any * more messages in the message queue. *

* 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. *

* 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. *

* * @return True if the looper looper has been asked to quit or false if the * thread had not yet started running. * * @see #quitSafely */public boolean quit() {Looper looper = getLooper(); if (looper != null) {looper.quit(); return true;}return false;}/** * Quits the handler thread's looper safely. *

* Causes the handler thread's looper to terminate as soon as all remaining messages * in the message queue that are already due to be delivered have been handled. * Pending delayed messages with due times in the future will not be delivered. *

* 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. *

* If the thread has not been started or has finished (that is if * {@link #getLooper} returns null), then false is returned. * Otherwise the looper is asked to quit and true is returned. *

* * @return True if the looper looper has been asked to quit or false if the * thread had not yet started running. */public boolean quitSafely() {Looper looper = getLooper(); if (looper != null) {looper.quitSafely(); return true;}return false;}/** * Returns the identifier of this thread. See Process.myTid(). */public int getThreadId() {return mTid;}}