Looper: 循环处理消息队列
//用法： 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(); } }//第一步，在TLS上创建一个Looper//TLS，thread local storage线程本地存储空间，也就是这个存储空间是和线程相关的，一个线程内有一个内部存储空间public static final void prepare() { if (sThreadLocal.get() != null) { throw new RuntimeException("Only one Looper may be created per thread"); } sThreadLocal.set(new Looper()); } /** * Run the message queue in this thread. Be sure to call * [email protected] #quit()} to end the loop. */// 从当前本地线程中得到loop对象，从中取出message队列，遍历其中的message并发送到其target// 注意msg.target.dispatchMessage(msg); public static final void loop() { Looper me = myLooper(); MessageQueue queue = me.mQueue; while (true) { Message msg = queue.next(); // might block //if (!me.mRun) { // break; //} if (msg != null) { if (msg.target == null) { // No target is a magic identifier for the quit message. return; } if (me.mLogging!= null) me.mLogging.println( ">>>>> Dispatching to " + msg.target + " " + msg.callback + ": " + msg.what ); msg.target.dispatchMessage(msg); if (me.mLogging!= null) me.mLogging.println( "<<<<< Finished to " + msg.target + " " + msg.callback); msg.recycle(); } } }// 再看看Handler中的该方法/** * Subclasses must implement this to receive messages. */ public void handleMessage(Message msg) { } /** * Handle system messages here. */ public void dispatchMessage(Message msg) { if (msg.callback != null) { handleCallback(msg); } else { if (mCallback != null) { if (mCallback.handleMessage(msg)) { return; } } handleMessage(msg); } }参考：http://blog.csdn.net/Innost/article/details/6055793