new Handler().post(new Runnalbe()... 分析

来源：互联网发布：软件开发模式有几种编辑：程序博客网时间：2024/06/10 16:41

Handler是很灵活的一个类，当运行下面的代码时：

new Handler().post(new Runnalbe(){@Overridepublic void run(){  //do something}});

它内部干了些啥？！

找到它的源代码：

    /**     * Causes the Runnable r to be added to the message queue.     * The runnable will be run on the thread to which this handler is      * attached.      *       * @param r The Runnable that will be executed.     *      * @return Returns true if the Runnable was successfully placed in to the      *         message queue.  Returns false on failure, usually because the     *         looper processing the message queue is exiting.     */    public final boolean post(Runnable r)    {       return  sendMessageDelayed(getPostMessage(r), 0);    }

sendMessageDelayed(getPostMessage(r), 0)的含义是立即发送了一个消息，再来看getPostMessage(r)的定义：

    private static Message getPostMessage(Runnable r) {        Message m = Message.obtain();        m.callback = r;        return m;    }

原来这里将Runnable赋给了Message.callcack。

总结：Runnalbe()的代码执行在Handler定义的线程中。

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