一、idleHandler是做什么的

/**
 * Callback interface for discovering when a thread is going to block
 * waiting for more messages.
 */
public static interface IdleHandler {
    /**
     * Called when the message queue has run out of messages and will now
     * wait for more.  Return true to keep your idle handler active, false
     * to have it removed.  This may be called if there are still messages
     * pending in the queue, but they are all scheduled to be dispatched
     * after the current time.
     */
    boolean queueIdle();
}

　　idleHandler是一个接口，消息队列空闲时执行的回调函数queieIdle()。queueIdle()函数返回值：

　　false：代表消息队列空闲时执行的Callback，执行完成后移除。

　　true：代表消息队列空闲时执行的Callback，在执行完成后不移除，当下次消息队列空休时再次被调用。