Android异步下载

[android]代码库

//前台ui线程在显示ProgressDialog，
//后台线程在下载数据，数据下载完毕，关闭进度框
@Override
public void onClick (View view) {
    switch (view.getId() ) {
    case R.id.btnFirst:
        dialog = ProgressDialog.show (this, "",
                                      "下载数据，请稍等 …", true, true);
        //启动一个后台线程
        handler.post (new Runnable() {
            @Override
            public void run() {
                //这里下载数据
                try {
                    URL  url = new URL (params);
                    HttpURLConnection conn  = (HttpURLConnection) url.openConnection();
                    conn.setDoInput (true);
                    conn.connect();
                    InputStream inputStream = conn.getInputStream();
                    bitmap = BitmapFactory.decodeStream (inputStream);
                    Message msg = new Message();
                    msg.what = 1;
                    handler.sendMessage (msg);

                } catch (MalformedURLException e1) {
                    e1.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });
        break;