ANDROID_MARS学习笔记_S02重置版_001_HanderLooperMessageThreadThreadLocal

Posted 2020-06-15

一、

*  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();
  *      }
  *  }

上述代码的执行流程为

1.Looper.prepare()会执行sThreadLocal.set(new Looper(quitAllowed))

2.而new Looper(quitAllowed)会执行，

(1)mQueue = new MessageQueue(quitAllowed);

(2)mThread = Thread.currentThread();

3.new Handler()会执行

(1)mLooper = Looper.myLooper();

(2)mQueue = mLooper.mQueue;

4.而myLooper();会执行return sThreadLocal.get();，所以保证handler当前线程只有一个looper

5.Looper.loop();会执行

(1)final MessageQueue queue = me.mQueue;

(2)for循环Message msg = queue.next();

(3)msg.target.dispatchMessage(msg);