Android的Thread & ProgressBar

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    />
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/progressbar_default"
/>
<ProgressBar
android:layout_width="fill_parent"
android:layout_height="wrap_content"
style="?android:attr/progressBarStyleHorizontal"
android:id="@+id/progressbar_Horizontal"
android:max="100"
/>

</LinearLayout>


//-----------------------soruce code--------------------------------

package android.demo.thread0;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ProgressBar;

public class Thread0_Activity extends Activity 
{

	ProgressBar bar0;
	ProgressBar bar1;
	boolean isRunning=false;
	
	
	Handler handler=new Handler() 
	{
        public void handleMessage(Message msg)//會從Message Queue取出Message 
        {
            bar0.incrementProgressBy(5);
            bar1.incrementProgressBy(5);
        }
    };



    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        bar0 = (ProgressBar)findViewById(R.id.progressbar_Horizontal);
        bar1 = (ProgressBar)findViewById(R.id.progressbar_default);
    }

    @Override
    public void onStart() 
    {
        super.onStart();
        bar0.setProgress(0);
        bar1.setProgress(0);

        //Thread background=new Thread(run0);
       // background.start();
        
        ProgressThread ProgressThread0=new ProgressThread();
        ProgressThread0.start();
    }
    
    private	Runnable run0=new Runnable()
	{

    	@Override
    	public void run()
    	{
    		// TODO Auto-generated method stub
    		try 
    		{
    			for (int i=0;i<20 /*&& isRunning*/;i++) 
    			{
    				Thread.sleep(1000);
    				handler.sendMessage(handler.obtainMessage());
    			}
    		}
    		catch (Throwable t) 
    		{
                    // just end the background thread
    		}
    	}
	};
	public class ProgressThread extends Thread
	{
		public void run()
		{
    		try 
    		{
    			for (int i=0;i<20 /*&& isRunning*/;i++) 
    			{
    				sleep(1000);
    				handler.sendMessage(handler.obtainMessage());
    			}
    		}
    		catch (Throwable t) 
    		{
                    // just end the background thread
    		}
		}
	};


}