Android Looper和Handler分析(9)

     * at the beginning and ending of each message dispatch, identifying the
     * target Handler and message contents.
     * 
     * @param printer A Printer object that will receive log messages, or
     * null to disable message logging.
     */ 
//设置调试输出对象，looper循环的时候会打印相关信息，用来调试用最好了。 
    public void setMessageLogging(Printer printer) { 
        mLogging = printer; 
    } 
     
    /**
     * Return the {@link MessageQueue} object associated with the current
     * thread.  This must be called from a thread running a Looper, or a
     * NullPointerException will be thrown.
     */ 
    public static final MessageQueue myQueue() { 
        return myLooper().mQueue; 
    } 
//创建一个新的looper对象， 
//内部分配一个消息队列，设置mRun为true 
    private Looper() { 
        mQueue = new MessageQueue(); 
        mRun = true; 
        mThread = Thread.currentThread(); 
    } 
 
    public void quit() { 
        Message msg = Message.obtain(); 
        // NOTE: By enqueueing directly into the message queue, the 
        // message is left with a null target.  This is how we know it is 
        // a quit message. 
        mQueue.enqueueMessage(msg, 0); 
    } 
 
    /**
     * Return the Thread associated with this Looper.
     */ 
    public Thread getThread() { 
        return mThread; 
    } 
    //后面就简单了，打印，异常定义等。 
    public void dump(Printer pw, String prefix) { 
        pw.println(prefix + this); 
        pw.println(prefix + "mRun=" + mRun); 
        pw.println(prefix + "mThread=" + mThread); 
        pw.println(prefix + "mQueue=" + ((mQueue != null) ? mQueue : "(null"));