Android Looper和Handler分析(2)

        } 
        sThreadLocal.set(new Looper()); 
    } 
     
    /** Initialize the current thread as a looper, marking it as an application's main 
     *  looper. The main looper for your application is created by the Android environment,
     *  so you should never need to call this function yourself.
     * {@link #prepare()}
     */ 
 //由framework设置的UI程序的主消息循环，注意，这个主消息循环是不会主动退出的  
//      
    public static final void prepareMainLooper() { 
        prepare(); 
        setMainLooper(myLooper()); 
//判断主消息循环是否能退出....  
//通过quit函数向looper发出退出申请  
        if (Process.supportsProcesses()) { 
            myLooper().mQueue.mQuitAllowed = false; 
        } 
    } 
 
    private synchronized static void setMainLooper(Looper looper) { 
        mMainLooper = looper; 
    } 
     
    /** Returns the application's main looper, which lives in the main thread of the application.
     */ 
    public synchronized static final Looper getMainLooper() { 
        return mMainLooper; 
    } 
 
    /**
     *  Run the message queue in this thread. Be sure to call
     * {@link #quit()} to end the loop.
     */ 
//消息循环，整个程序就在这里while了。  
//这个是static函数喔！  
    public static final void loop() { 
        Looper me = myLooper();//从该线程中取出对应的looper对象  
        MessageQueue queue = me.mQueue;//取消息队列对象...  
        while (true) { 
            Message msg = queue.next(); // might block取消息队列中的一个待处理消息..  
            //if (!me.mRun) {//是否需要退出？mRun是个volatile变量，跨线程同步的，应该是有地方设置它。