安卓Handler和Looper的假想

if (Looper.myLooper() != Looper.getMainLooper()) {

// If we finish marking off of the main thread, we need to

// actually do it on the main thread to ensure correct ordering.

Handler mainThread = new Handler(Looper.getMainLooper());

mainThread.post(new Runnable() {

@Override

public void run() {

mEventLog.add(tag, threadId);

mEventLog.finish(this.toString());

}

});

return;

}

handler里面持有一个Looper,Looper里面持有一个消息队列MessageQueue

handler首先会把消息Post到它所持有的Looper的消息队列之中，

Looper循环者从消息队列中拿到消息后进行处理