Android文件下载进度条的实现代码

main.xml：
代码如下:

<?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);  }   }