Android handle-message的发送与处理案例详解

　　/**

　　* 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();//返回保存在调用线程TLV中的Looper对象

　　if (me == null) {

　　throw new RuntimeException("No Looper; Looper.prepare() wasn't called on this thread.");

　　}

　　final MessageQueue queue = me.mQueue;//取得Looper对象的消息队列

　　// 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 取消息队列中的一个待处理消息

　　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);//调用该消息的Handle,交给它的dispatchMessage函数处理

　　}

　　}