Android文件下载进度条的实现代码

<?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>

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);
 } 
}