handler
Handler中分发消息的一些方法
post(Runnable)
postAtTime(Runnable,long)
postDelayed(Runnable long)
sendEmptyMessage(int)
sendMessage(Message)
sendMessageAtTime(Message,long)
sendMessageDelayed(Message,long)
以上post类方法允许你排列一个Runnable对象到主线程队列中, sendMessage类方法, 允许你安排一个带数据的Message对象到队列中,等待更新.