Android线程显示进度框

package com.test.threadtest1;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
/**
 * 
 * @author Sean
 *
 */

public class ThreadTest1Activity extends Activity {
    private Button btn;
    private Thread mThread;
    private static final int PROGRESS_DIALOG=10;
    ProgressDialog progressDialog=null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_thread_test1);
        btn=(Button)findViewById(R.id.button1);
        btn.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                //创建新线程
                mThread = new Thread(runable);
                mThread.start();
                //主线程执行UI更新显示
                showDialog(PROGRESS_DIALOG);
            }
        });
        
    }
    private Handler mHandler=new Handler(){
        public void handleMessage(Message msg){
            switch(msg.what)
            {
            case 300:
                if(msg.arg1==msg.arg2)
                {   //移除对话框
                    removeDialog(PROGRESS_DIALOG);
                }
                else
                {  //显示进度
                    progressDialog.setProgress(msg.arg1*100/msg.arg2);
                }
            }    
        }
    };
    //创建Dialog样式
    protected Dialog onCreateDialog(int id){
        switch(id)
        {
        case PROGRESS_DIALOG:
            progressDialog= new ProgressDialog(this);
            progressDialog.setTitle("后台处理");
            progressDialog.setMessage("请稍候，正在处理。。。");
            progressDialog.setIndeterminate(false);
            progressDialog.setCancelable(true);
            progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            progressDialog.setProgress(0);
            return progressDialog;
        }
        return super.onCreateDialog(id);
        
    }
    //创建Runnable执行后台任务
    Runnable runable=new Runnable() {
        
        @Override
        public void run() {
            // TODO Auto-generated method stub
            int total=100;
            int current=0;
            while(current<=total)
            {
                try {
                    //模拟进程时间
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                Message msg=mHandler.obtainMessage(300);
                msg.arg2=total;
                msg.arg1=current;
                current+=10;
                mHandler.sendMessage(msg);
            }
        }
    };
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_thread_test1, menu);
        return true;
    }

}