android Handler and progress

package zhou.demo;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
/**
* 异步的消息处理机制
* @author Administrator
*
*/
public class HandlerProgress extends Activity {
    private ProgressBar bar =null;
    private Button startButton = null;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        bar = (ProgressBar)findViewById(R.id.bar);
        startButton = (Button)this.findViewById(R.id.startButton);
        startButton.setOnClickListener(new OnClickListener(){
   public void onClick(View v) {
    bar.setVisibility(View.VISIBLE);
    updateBarHandler.post(updateThread);
   }

        });
    }
    /**
     * 使用匿名内部类复写
     */
    Handler updateBarHandler = new Handler(){
    public void handleMessage(Message msg){
      bar.setProgress(msg.arg1);
      updateBarHandler.post(updateThread);//加入线程队列
    }
    };
    Runnable updateThread = new Runnable(){
    int i = 0;
  public void run() {
   System.out.println("开始线程");
   i += 1;
   Message msg = updateBarHandler.obtainMessage();
   msg.arg1 = i;
   try {
    Thread.sleep(100);
   } catch (Exception e) {
    // TODO: handle exception
   }
   updateBarHandler.sendMessage(msg);//压入消息队列
   if(i == 100){
    updateBarHandler.removeCallbacks(updateThread);
   }
  }

    };
}

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