java - 我如何应用alertDialog作为AsyncTask中的服务器响应

Question

我正在尝试通过 cPanel 托管将我的项目 app 与在线数据库连接。我使用了AlertDialog.Builder、setOnClickListener、 用于显示服务器的响应，但似乎我遇到了一些错误，任何答案将不胜感激，谢谢

这是我的 java 文件。

//Calling my AsyncTask
@Override
 public void onClick(View view) {
 view.setEnabled(false);
 Intent launchactivity = new Intent(MainActivity.this,MainActivity.class);
 startActivity(launchactivity);

            tvscancontent = tvScanContent.getText().toString();
            tvscanformat = tvScanFormat.getText().toString();
            BackgroundTask backgroundTask = new BackgroundTask();
            backgroundTask.execute(tvscancontent,tvscanformat);
            finish();

            showShowView2();
           // displaynotification();

        }

    });

private class BackgroundTask extends AsyncTask<String,Void,String> { // i got crash here

        Context context;
        String add_info_url;
        private Object activity;




        public BackgroundTask() {

        }

        @Override
        protected void onPreExecute() {


            add_info_url = "http://www.d48.asia/shan/index.php";

            progressDialog = new ProgressDialog(MainActivity.this);
            progressDialog.setTitle("Processing...");
            progressDialog.setMessage("Authenticating...");
            progressDialog.setCancelable(false);
            progressDialog.setIndeterminate(true);
            progressDialog.setProgressStyle(progressDialog.STYLE_SPINNER);
            progressDialog.show();



        }

        @Override
        protected String doInBackground(String... args) {

            String tvscancontent = args[0];
            String tvscanformat = args[1];
            String response = "";
            String line = "";

            try {
                URL url = new URL(add_info_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
                String data_string = URLEncoder.encode("tvscancontent", "UTF-8") + "=" + URLEncoder.encode(tvscancontent, "UTF-8")+ "&" +
                        URLEncoder.encode("tvscanformat", "UTF-8") + "=" + URLEncoder.encode(tvscanformat, "UTF-8");
                bufferedWriter.write(data_string);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));

                while ((line = bufferedReader.readLine()) != null){

                    response+= line;


                }


                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();

                return response;


            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }


            return null;


        }

        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);

        }

     //Server response
        @Override
        protected void onPostExecute(final String result) {
            //Toast toast =Toast.makeText(getApplicationContext(), result, Toast.LENGTH_LONG);
            //toast.setGravity(Gravity.CENTER ,0,0);
            //toast.show();
                AlertDialog.Builder alert = new AlertDialog.Builder(context); // also i got crash here
                    alert.setTitle("Third Wheel Response");
                    alert.setMessage(result);
                    alert.setCancelable(false);
                    alert.setPositiveButton("ok", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                          dialogInterface.cancel();
                        }
                    });
                    AlertDialog dialogs = alert.create();
                    dialogs.show();


                if (progressDialog != null) {
                    progressDialog.dismiss();
                    SaveData.setEnabled(true);

                }

错误:

11-10 08:40:23.174 4815-4815/com.thethirdwheelproject.thirdwheel E/AndroidRuntime:致命异常:main 进程:com.thethirdwheelproject.thirdwheel，PID:4815 android.view.WindowManager$BadTokenException:无法添加窗口—— token android.os.BinderProxy@bc0afcf 无效；您的 Activity 正在运行吗？ 在 android.view.ViewRootImpl.setView(ViewRootImpl.java:678) 在 android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:342) 在 android.view.WindowManagerImpl.addView(WindowManagerImpl.java:93) 在 android.app.Dialog.show(Dialog.java:316) 在 com.thethirdwheelproject.thirdwheel.MainActivity$BackgroundTask.onPostExecute(MainActivity.java:489) 在 com.thethirdwheelproject.thirdwheel.MainActivity$BackgroundTask.onPostExecute(MainActivity.java:389) 在 android.os.AsyncTask.finish(AsyncTask.java:660) 在 android.os.AsyncTask.-wrap1(AsyncTask.java) 在 android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:677) 在 android.os.Handler.dispatchMessage(Handler.java:102) 在 android.os.Looper.loop(Looper.java:154) 在 android.app.ActivityThread.main(ActivityThread.java:6077) 在 java.lang.reflect.Method.invoke( native 方法) 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756) 11-10 08:40:23.733 1334-1334/？ E/EGL_emulation:tid 1334:eglCreateSyncKHR(1901):错误0x3004(EGL_BAD_ATTRIBUTE)

Answer 1

Your context variable is not initialized

删除您的 context 变量并使用 MainActivity.this。

试试这个方法

@Override
 public void onClick(View view) {
 view.setEnabled(false);
            tvscancontent = tvScanContent.getText().toString();
            tvscanformat = tvScanFormat.getText().toString();
            BackgroundTask backgroundTask = new BackgroundTask();
            backgroundTask.execute(tvscancontent,tvscanformat);
            showShowView2();
           // displaynotification();

        }

    });