Handler，Looper分析

【Handler.java】

final MessageQueue mQueue;

final Looper mLooper;

final Callback mCallback;

public Handler() {

//获得调用线程的Looper

    mLooper = Looper.myLooper();

    if (mLooper == null) {

        throw new RuntimeException(...);

    }

//得到 Looper的消息队列

    mQueue = mLooper.mQueue;

}