Android实现文件下载进度显示功能

和大家一起分享一下学习经验，如何实现Android文件下载进度显示功能，希望对广大初学者有帮助。
先上效果图：

上方的蓝色进度条，会根据文件下载量的百分比进行加载，中部的文本控件用来现在文件下载的百分比，最下方的ImageView用来展示下载好的文件，项目的目的就是动态向用户展示文件的下载量。

下面看代码实现：首先是布局文件：

接下来的主Activity代码：

public class MainActivity extends Activity {
 
  ProgressBar pb; 
  TextView tv;
  ImageView imageView;
  int fileSize;  
  int downLoadFileSize;  
  String fileEx,fileNa,filename; 
  //用来接收线程发送来的文件下载量，进行UI界面的更新
  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(MainActivity.this, "文件下载完成", Toast.LENGTH_SHORT).show(); 
 FileInputStream fis = null;
 try {
   fis = new FileInputStream(Environment.getExternalStorageDirectory() + File.separator + "/ceshi/" + filename);
 } catch (FileNotFoundException e) {
   e.printStackTrace();
 }
 Bitmap bitmap = BitmapFactory.decodeStream(fis); ///把流转化为Bitmap图
 imageView.setImageBitmap(bitmap);
 break;  
   
case -1:  
 String error = msg.getData().getString("error");
 Toast.makeText(MainActivity.this, error, Toast.LENGTH_SHORT).show();  
 break;  
      }  
     }  
     super.handleMessage(msg);  
    }  
   };
   
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    pb=(ProgressBar)findViewById(R.id.progressBar);
    tv=(TextView)findViewById(R.id.textView);
    imageView = (ImageView) findViewById(R.id.imageView);
    tv.setText("0%");
    new Thread(){
      public void run(){
 try {
   //下载文件，参数：第一个URL，第二个存放路径
   down_file("http://cdnq.duitang.com/uploads/item/201406/15/20140615203435_ABQMa.jpeg", Environment.getExternalStorageDirectory() + File.separator + "/ceshi/");
 } 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");
    File file1 = new File(path);
    File file2 = new File(path+filename);
    if(!file1.exists()){
      file1.mkdirs();
    }
    if(!file2.exists()){
      file2.createNewFile();
    }
    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);  
    }  
   
  }  
   
  //在线程中向Handler发送文件的下载量，进行UI界面的更新
  private void sendMsg(int flag)  
  {  
    Message msg = new Message();  
    msg.what = flag;  
    handler.sendMessage(msg);  
  }    
   
}

最后一定要注意的是：在AndroidManifest.xml文件中，添加访问网络的权限

到这里关于Android文件下载动态显示下载进度的内容就为大家分享完毕，希望对大家的学习有所帮助。