Looper Handler 多线程

最新推荐文章于 2025-09-05 18:39:19 发布

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最新推荐文章于 2025-09-05 18:39:19 发布

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CC 4.0 BY-SA版权

文章标签： ui

原文链接：http://www.cnblogs.com/webglcn/p/4473466.html

本文详细介绍了Android中Looper与Handler的工作原理及其实现机制。解释了Looper如何在主线程中创建并循环处理消息队列，以及Handler如何通过关联Looper发送和接收消息。此外还涉及了不同线程间消息传递的过程。

Looper is created by default on main UI
   Property:
       // main ui thread, if Looper is initialized in another thread, it would be a new thread
       // class xx extends Thread. => here is a new thread.
       mThread
       mMessageQueue // empty
   loop()
       for(;;) {
           message = mMessageQueue.next()
           message.target.dispatchMessage(message);
       }

Handler
   Property:
       mLooper = Looper.myLooper();
        mQueue = mLooper.mQueue;
        mCallback = callback;

   sendMessage
       mQueue.enqueueMessage(msg, uptimeMillis);

   interface Callback {
        public boolean handleMessage(Message msg);
    }

   dispatchMessage(Message msg) { // ingore Message's properties
        if (mCallback != null) {
            if (mCallback.handleMessage(msg)) {
                return;
            }
        }
        handleMessage(msg);
    }

handler make connection with Looper by adding looper object into handler.
handler from thread A sends message to looper.MQ
MQ is looped in thread B.
Looper processed MQ messages by sequence from different threads.