android - 为什么我使用 AsyncTask 时会出现 android.os.NetworkOnMainThreadException？

Question

我在 AsynkTask 中编写网络操作代码时出现 android.os.NetworkOnMainThreadException。抛出这个异常还有其他原因吗？

这是我的代码:

public class Background_confirmation extends AsyncTask<Void, Integer, Void> {
        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            progressDialog = ProgressDialog.show(Confirmation.this,
                    "Please wait...", "Retrieving data ...", true);
            try {
                HttpClient httpclient = new DefaultHttpClient();

                HttpPost httppost = new HttpPost(
                        "http://68.121.167.160/sip_chat_api/create_account.php?useralias="
                                + useralias + "&cntname=" + cntcode + "");
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity entity = response.getEntity();
                    is = entity.getContent();


            } catch (Exception e) {
                e.printStackTrace();
            }
            if (backgroung_flag == 1) {

            } else {
                if (is != null) {
                    try {
                        BufferedReader reader = new BufferedReader(
                                new InputStreamReader(is, "UTF-8"));
                        StringBuilder sb = new StringBuilder();
                        String line = null;
                        while ((line = reader.readLine()) != null) {
                            sb.append(line + "\n");
                        }
                        is.close();

                        result = sb.toString();
                    } catch (Exception e) {
                        Log.e("log_tag",
                                "Error converting result " + e.toString());
                    }
                }

            }
            super.onPreExecute();
        }

        @Override
        protected Void doInBackground(Void... params) {
            // TODO Auto-generated method stub

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            if (progressDialog.isShowing()) {
                progressDialog.dismiss();
                // progressDialog.setCancelable(true);
            }
            super.onPostExecute(result);
        }

    }

我在 OnCreate() 中调用这个类

new Background_confirmation().execute();

但它总是进入 Catch block 并给我 this异常 LogCat
任何建议和想法将不胜感激。
谢谢

Answer 1

您使用了错误的 AsyncTask 方法来放置您的网络相关代码。请将它移动到 doInBackground，因为 onPreExecute 发生在主线程上。于是，异常发生了。详情为here .