Android文件下载进度条的实现

<?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:id="@+id/tv"  
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:text=""  
    />  
<ProgressBar android:id="@+id/down_pb"  
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"  
    android:max="100"  
    style="?android:attr/progressBarStyleHorizontal" mce_style="?android:attr/progressBarStyleHorizontal"  
/>  
</LinearLayout> 

main.java:

package com.pocketdigi.download;  
   
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.InputStream;  
import java.net.URL;  
import java.net.URLConnection;  
   
import org.apache.http.client.ClientProtocolException;  
import android.app.Activity;  
import android.os.Bundle;  
import android.os.Handler;  
import android.os.Message;  
import android.util.Log;  
import android.widget.ProgressBar;  
import android.widget.TextView;  
import android.widget.Toast;  
   
public class main extends Activity {  
    /** Called when the activity is first created. */  
    ProgressBar pb;  
    TextView tv;  
    int   fileSize;  
    int   downLoadFileSize;  
    String fileEx,fileNa,filename;  
    private Handler handler = new Handler()  
      {  
        @Override  
        public void handleMessage(Message msg)  
        {//定义一个Handler，用于处理下载线程与UI间通讯  
          if (!Thread.currentThread().isInterrupted())  
          {  
            switch (msg.what)  
            {  
              case 0:  
                pb.setMax(fileSize);  
              case 1:  
                pb.setProgress(downLoadFileSize);  
                int result = downLoadFileSize * 100 / fileSize;  
                tv.setText(result + "%");  
                break;  
              case 2:  
                Toast.makeText(main.this, "文件下载完成", 1).show();  
                break;  
   
              case -1:  
                String error = msg.getData().getString("error");  
                Toast.makeText(main.this, error, 1).show();  
                break;  
            }  
          }  
          super.handleMessage(msg);  
        }  
      };  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
        pb=(ProgressBar)findViewById(R.id.down_pb);  
        tv=(TextView)findViewById(R.id.tv);  
        new Thread(){  
            public void run(){  
                try {  
       down_file("http://wallpaper.pocketdigi.com/upload/1/bigImage/1284565196.jpg",
"/sdcard/");  
                    //下载文件，参数：第一个URL，第二个存放路径  
                } catch (ClientProtocolException e) {  
                    // TODO Auto-generated catch block  
                    e.printStackTrace();  
                } catch (IOException e) {  
                    // TODO Auto-generated catch block  
                    e.printStackTrace();  
                }  
            }  
        }.start();  
   
   
    }  
    public void down_file(String url,String path) throws IOException{  
        //下载函数        
        filename=url.substring(url.lastIndexOf("/") + 1);  
        //获取文件名  
        URL myURL = new URL(url);  
        URLConnection conn = myURL.openConnection();  
        conn.connect();  
        InputStream is = conn.getInputStream();  
        this.fileSize = conn.getContentLength();//根据响应获取文件大小  
        if (this.fileSize <= 0) throw new RuntimeException("无法获知文件大小 ");  
        if (is == null) throw new RuntimeException("stream is null");  
        FileOutputStream fos = new FileOutputStream(path+filename);  
        //把数据存入路径+文件名  
        byte buf[] = new byte[1024];  
        downLoadFileSize = 0;  
        sendMsg(0);  
        do  
          {  
            //循环读取  
            int numread = is.read(buf);  
            if (numread == -1)  
            {  
              break;  
            }  
            fos.write(buf, 0, numread);  
            downLoadFileSize += numread;  
   
            sendMsg(1);//更新进度条  
          } while (true);  
        sendMsg(2);//通知下载完成  
        try  
          {  
            is.close();  
          } catch (Exception ex)  
          {  
            Log.e("tag", "error: " + ex.getMessage(), ex);  
          }  
   
    }  
    private void sendMsg(int flag)  
    {  
        Message msg = new Message();  
        msg.what = flag;  
        handler.sendMessage(msg);  
    }      
   
   
}