安卓handler.post问题

 1 protected void onCreate(Bundle savedInstanceState) {

 2         super.onCreate(savedInstanceState);

 3         setContentView(R.layout.activity_main);

 4         btn = (Button) findViewById(R.id.button1);

 5         progressBar = (ProgressBar) findViewById(R.id.progressBar1);

 6         

 7         btn.setOnClickListener(new OnClickListener() {

 8             @Override

 9             public void onClick(View v) {

10                 // 立即把消息加到消息队列中,postDelayed(r,3000)延迟3秒加到消息队列

11                 handler.post(r);

12             }

13         });

14     }

15 

16     Handler handler = new Handler() {

17         public void handleMessage(android.os.Message msg) {

18             progressBar.setProgress(msg.arg1);

19             handler.post(r);

20 

21             if (i == 80)

22                 // 移除消息

23                 handler.removeCallbacks(r);

24         };

25 

26     };

27     int i = 0;

28     Runnable r = new Runnable() {

29 

30         @Override

31         public void run() {

32             i = i + 10;

33             message = new Message();

34             message.arg1 = i;

35 

36             try {

37                 Thread.sleep(1000);

38             } catch (InterruptedException e) {

39                 // TODO Auto-generated catch block

40                 e.printStackTrace();

41             }

42 

43             handler.sendMessage(message);

44 

45         }

46     };

47 }

在第11行不是使用post启动线程r了吗,为什么在第19行还要再post一次??求指点