Android更新下载进度条

推荐安卓开发神器（里面有各种UI特效和android代码库实例）

下载文件会阻塞UI主线程，所以需要new一个新线程来执行下载操作，通过handler执行更新UI进度条操作。代码如下：

public class AndroidTest extends Activity {  
    private static final String TAG = "AndroidTest";  
  
    private ProgressBar progressBar = null;  
    private Button startButton = null;  
    private EditText filenameText = null;  
    private MyHandler handler = null;  
  
    private Message message = null;  
    private boolean flag = true;  
    private int size = 1;  
    private int hasRead = 0;  
    private int len = 0;  
    private byte buffer[] = new byte[1024*4];  
    private int index = 0;   
      
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
          
        progressBar = (ProgressBar)findViewById(R.id.progress_horizontal);  
        startButton = (Button)findViewById(R.id.mybutton);  
        startButton.setOnClickListener(new ButtonClick());  
      
        filenameText = (EditText)findViewById(R.id.fileNameID);  
      
        handler = new MyHandler();  
    }  
  
  
    public boolean downloadFile(final String urlStr, final String filename) {  
        new Thread(new Runnable(){    
            public void run() {   
                try {  
                    URL url = new URL(urlStr);  
                    HttpURLConnection connection = (HttpURLConnection)url.openConnection();  
                    size = connection.getContentLength();  
                    InputStream inputStream = connection.getInputStream();  
                    OutputStream outputStream = new FileOutputStream(Environment.getExternalStorageDirectory()+"/"+filename);  
                      
                    while((len=inputStream.read(buffer))!=-1){  
                        outputStream.write(buffer);  
                        hasRead+=len;  
                        index = (int)(hasRead*100)/size;  
                        message = new Message();  
                        message.what = 1;  
                        handler.sendMessage(message);  
                        Log.d(TAG, "index = " + index);  
                        System.out.println("has = "+hasRead+" size = "+size+" index = "+index);  
                    }  
                  
                    inputStream.close();  
                    outputStream.close();  
                } catch (Exception e) {  
                    flag = false;  
                    e.printStackTrace();  
                }  
            }  
        }).start();  
          
        return flag;  
    }  
  
    class ButtonClick implements OnClickListener {  
  
        public void onClick(View v) {  
      
            String url = filenameText.getText().toString();  
            String filename = url.substring(url.lastIndexOf('/') + 1);  
            Log.d(TAG, "url = " + url);  
            Log.d(TAG, "filename = " + filename);  
              
            if(!downloadFile(url, filename)) {  
                String rs = "下载失败 ";  
                Toast.makeText(AndroidTest.this, rs, Toast.LENGTH_SHORT).show();  
            }  
      
        }  
  
    }  
  
    class MyHandler extends Handler{  
  
        @Override  
        public void handleMessage(Message msg) {  
            if (msg.what == 1) {  
                progressBar.setProgress(index);  
                Log.d(TAG, "setProgress index:" + index);  
                if (index >= 99) {  
                    String rs = "下载完成";  
                    Toast.makeText(AndroidTest.this, rs, Toast.LENGTH_SHORT).show();  
                }  
            }  
              
            super.handleMessage(msg);  
        }  
  
    }  
  
}