android_handler(二)

package cn.com.sxp;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;

public class HandlerTwoActivity extends Activity {
    private ProgressBar progressBar;
    private Button startButton;
    /** Called when the activity is first created. */
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        progressBar = (ProgressBar)findViewById(R.id.progressbar);
        startButton = (Button)findViewById(R.id.startButton);

        startButton.setOnClickListener(new buttonOnClickListener());
    }
    
    class buttonOnClickListener implements OnClickListener{ 
        public void onClick(View v) {
            // 点击一下进度条就可见
            progressBar.setVisibility(View.VISIBLE); 
            updateBarHandler.post(updateThread); 
        }
    }
        

    Handler updateBarHandler = new Handler(){
        @Override 
        public void handleMessage(Message msg) { 
            progressBar.setProgress(msg.arg1); 
            // 將要執行的線程放入隊列中
            updateBarHandler.post(updateThread);
        } 
    }; 

    Runnable updateThread = new Runnable(){ 
        int counter = 0; 
        public void run() { 
            // TODO Auto-generated method stub 
            Log.d("in updateThread run()","在updateThread run方法中"); 
            counter += 10; 
            // 从系统处得到一个消息 
            // Returns a new Message from the global message pool. More efficient than creating and allocating new instances. The retrieved message has its handler 
            // set to this instance (Message.target == this). If you don't want that facility, just call Message.obtain() instead. 
            Message msg = updateBarHandler.obtainMessage(); 
            //将Message对象的arg1参数的值设置为i 
            // arg1 and arg2 are lower-cost alternatives to using setData() if you only need to store a few integer values. 
            msg.arg1 = counter; //用arg1、arg2这两个成员变量传递消息，优点是系统性能消耗较少 
            try { 
                Thread.sleep(1000); //让当前线程休眠1000毫秒 
            }catch(InterruptedException ex){ 
                ex.printStackTrace(); 
            } 
            //将Message对象加入到消息队列当中 
            updateBarHandler.sendMessage(msg);
            if (100 == counter){
                updateBarHandler.removeCallbacks(updateThread); 
            } 
       } 
   }; 
}

运行效果如下：

点击“点我”，日志打印如下：

但是当我退出这个活动，这个线程还在输出，显然线程没有停止，因此这里必须得让handler清除队列中的消息。