private String url=”http://www.oschina.NET/uploads/osc-Android-v2.6.4-release.apk”; 
private String sdPath = “/sdcard/” + System.currentTimeMillis() + “yuyin.apk”; 

HttpUtils httpUtils=new HttpUtils(); 
//参数一:下载的路径 参数二:下载到sdpath的路径 参数三: 
httpUtils.download(url, sdPath, true, new RequestCallBack() {

  @Override
  public void onSuccess(ResponseInfo<File> arg0) {
    mBtn.setText("下载完成");
    //路径
    String path = arg0.result.getPath();
    File file = new File(path);
    Intent intent = new Intent(Intent.ACTION_VIEW); 
     intent.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive"); 
    startActivity(intent);
  }

  @Override
  public void onFailure(HttpException arg0, String arg1) {
    mBtn.setText("下载失败");
  }
  @Override
  public void onLoading(long total, long current, boolean isUploading) {
    // TODO Auto-generated method stub
    super.onLoading(total, current, isUploading);
    mBtn.setText("正在下载.....");

  }
  @Override
  public void onStart() {
    super.onStart();
    mBtn.setText("开始下载");
  }
});