Handler
#mQueue:MessageQueue#mLooper:Looper
+dispatchMessage(msg:Message)+handleMessage(msg:Message)+obtainMessage():Message+sendMessage(msg:Message)+removeMessages()
MessageQueue
#mMessages:Message
Handler有mQueue和mLooper对象
+Message有一个Handler对象
Looper
#sThreadLocal:ThreadLocal<Looper>-mMainLooper:static Looper#mQueue:MessageQueue#mThread: Thread
+ preapre()+loop()+myLooper()+quit()
Message
+what:int+arg1: int+arg2:int+obj: Object#when:long#target:Handler#next:Message
+Obtain():Message+recycle()
+MessageQueuey有一个mMessages消息
+Looper有一个mQueue消息队列
