Android文件下载进度条的实现

main.xml：

<?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);
    }


}