Android中Handler的sendEmptyMessage的理解

在写代码的过程中，碰到一行代码不理解，去看了下源码，来记录下。

mHandler.sendEmptyMessage(0);

sendEmptyMessage这个方法之前没有碰到过，查阅源码后发现：

    /**     * Sends a Message containing only the what value.     *       * @return Returns true if the message 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 sendEmptyMessage(int what)    {        return sendEmptyMessageDelayed(what, 0);    }

发现底层调用了sendEmptyMessageDelayed方法，

这个的解释是，只发送一个包含what值的message。

继续看源码：

    /**     * Sends a Message containing only the what value, to be delivered     * after the specified amount of time elapses.     * @see #sendMessageDelayed(android.os.Message, long)      *      * @return Returns true if the message 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 sendEmptyMessageDelayed(int what, long delayMillis) {        Message msg = Message.obtain();        msg.what = what;        return sendMessageDelayed(msg, delayMillis);    }

看到这里就知道了，确实发送了一个只包含what值的消息。

确实，不看源码的话，完全不知道这个方法到底做了什么，看来以后还是要多多阅读源码。