需要异步处理，所以构造一个异步处理的类
//异步任务处理
class RequestNetworkDataTask extends AsyncTask<String, Integer, String> {
//在后台处理之前触发
//这个在主线程中
@Override
protected void onPreExecute() {
super.onPreExecute();
}

    //后台处理    
    //这个在另一个线程执行    
    @Override    
    protected String doInBackground(String... params) {
        //此处的RequestData()是自己封装的返回网络请求的一个方法
        String result = RequestData(params[0]);
        return result;   
    }   

    //后台处理完之后
    //这个在主线程中执行    
    //里面的参数s是doInBackground()的返回结果    
    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);        
        mTvResult.setText(s); 
    }
}
/*--------------------------------------------------------------------*/
//请求网络数据
private String RequestData(String urlString) {    
    try {        
        URL url = new URL(urlString);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();       
        //设置超时时间
        connection.setConnectTimeout(30000); 
        connection.setRequestMethod("GET"); 
        connection.connect(); 
        int responsecode = connection.getResponseCode(); 
        String responseMessage = connection.getResponseMessage();    
        String result = null;
        if (responsecode == HttpURLConnection.HTTP_OK) { 
            InputStream inputStream = connection.getInputStream();   
            Reader reader = new InputStreamReader(inputStream, "UTF-8");         
            char[] buffer = new char[1024];
            reader.read(buffer); 
            result = new String(buffer); 
        } 
        return result; 
    } catch (MalformedURLException e) {      
        e.printStackTrace();    
    } catch (IOException e) {  
        e.printStackTrace();  
    } 
    return null;
}

写完方法后就new刚才的类，即
//url是一个链接地址
new RequestNetworkDataTask().execute(url);