NetworkOnMainThreadException android 活动[重复]

我正在使用此代码来检索 android 活动中的网站数据。它抛出 android.os.networkonmainthreadexception

    try
        {
            URL url = new URL("https://enigmatic-woodland-35608.herokuapp.com/pager.json");
            URLConnection tc = url.openConnection();
            BufferedReader in = new BufferedReader(new InputStreamReader(
                    tc.getInputStream()));
            String line, newl = " ";
            while ((line = in.readLine()) != null) {
                newl += line.trim();
            }
            System.out.println("newl" + newl.trim());
        } catch (Exception e) {
            Log.e("exception", e.toString());
        }

请给我一个可能的解决方案..

网络操作/调用不能在主线程中完成。您需要从另一个线程、异步任务或意向服务运行它

注意：所有 UI 操作都应该在 onPostExecute,onPreExecute 完成

下面的代码或许可以帮助你解决。

在你想要的地方调用 AsyncTask

new PagerAsyncTask().execute();

class PagerAsyncTask extends AsyncTask<String,Void,String>{
            @Override
            protected void onPreExecute() {
                super.onPreExecute();
            }

        @Override
        protected String doInBackground(String... params) {
            StringBuilder sb=null;
            BufferedReader reader=null;
            String serverResponse=null;
            try {

                URL url = new URL(""https://enigmatic-woodland-35608.herokuapp.com/pager.json"");
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
                connection.setConnectTimeout(5000);
                connection.setRequestMethod("GET");
                connection.connect();
                int statusCode = connection.getResponseCode();
                //Log.e("statusCode", "" + statusCode);
                if (statusCode == 200) {
                    sb = new StringBuilder();
                    reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                    String line;
                    while ((line = reader.readLine()) != null) {
                        sb.append(line + "\n");
                    }
                }

                connection.disconnect();
                if (sb!=null)
                    serverResponse=sb.toString();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
            return serverResponse;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
           //All your UI operation can be performed here
            //Response string can be converted to JSONObject/JSONArray like
            JSONObject response=new JSONObject(s);
            System.out.println(s);
        }
    }