Android通过HttpURLConnection链接到网络，并获取网络数据

1.判断网络是否连接

    private void networkIsconnected(String str){
        ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        if (networkInfo != null && networkInfo.isConnected()){
            new DownloadUrl(str).execute();
        }else {
            display.setText("网络没有链接上！");
        }
    }

2.创建一个任务类，实现网络下载后台执行

    //创建一个任务类
    private class DownloadUrl extends AsyncTask<Integer,Integer,String>{
        private String str ;

        public DownloadUrl(String url){
            this.str = url;
        }

        @Override
        protected String doInBackground(Integer... urls) {
            try {
                return downloadurl(str);
            } catch (IOException e) {
                return "网络地址错误！";
            }
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            display.setText(s);
        }
    }

3.创建一个下载数据的函数

    //根据url下载数据内容
    private String downloadurl(String url) throws IOException {

        InputStream is = null;
        int len = 500;

        URL myurl = new URL(url);
        HttpURLConnection conn = (HttpURLConnection) myurl.openConnection();
        conn.setConnectTimeout(10000);
        conn.setReadTimeout(15000);
        conn.setDoInput(true);
        conn.connect();
        int response = conn.getResponseCode();
        Log.d("DEBUG_TAG", "The response is: " + response);
        is = conn.getInputStream();
        String contengString = readIt(is,len);
        return contengString;
    }

4.读取输入流传过来的inputstream

    public String readIt(InputStream stream, int len) throws IOException{
        Reader reader = null;
        reader = new InputStreamReader(stream, "UTF-8");
        char[] buffer = new char[len];
        reader.read(buffer);
        return new String(buffer);
    }

5.最后在oncreate中直接运行即可

networkIsconnected(urltext.getText().toString());