java - 在进度对话框中嵌套警报对话框

Question

我是 android 的新手，我正在开发一个通过 PHP 将数据从 android 传递到 MySQL 的应用程序。现在我正在尝试验证登录 ID 和密码。如果没有设置任何一个字段，或者如果登录 ID 和密码错误我想显示一个警告对话框，通知用户登录 ID 或密码不正确。为此我编写了以下代码。

public class HomeActivity extends Activity 
{

    JSONParser jsonParser = new JSONParser();
    private ProgressDialog pDialog;
    private static String url_check_voter = "http://10.0.2.2/evoting/check_voter.php";
    private EditText getUserId;
    private EditText getPassword;
    private Button btnLogin;//private Button btnRegister;
    private TextView lblResult;
    private Button btnRegister;
    AlertDialog.Builder alertDialogBuilder;

    String TAG_SUCCESS="success" ;

    @Override
    public void onCreate(Bundle savedInstanceState) 
    {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.home_activity);
        getUserId = (EditText)findViewById(R.id.getLoginIdTxt);
        getPassword = (EditText)findViewById(R.id.getPasswordTxt);

        btnLogin = (Button) findViewById(R.id.btnLogin);
        btnRegister = (Button) findViewById(R.id.btnRegister);




         btnRegister.setOnClickListener(new View.OnClickListener()
         {
             public void onClick(View view) 
             {

             Intent i = new Intent(getApplicationContext(), RegisterActivity.class);
             startActivity(i);
             }

         });



 // Set Click Listener
         btnLogin.setOnClickListener(new View.OnClickListener() 
         {

             public void onClick(View view) 
             {
                new CheckVoter().execute();
               // Check Login
                 /* String userid = getUserId.getText().toString();
                  String password = getPassword.getText().toString();

                  if(userid.equals(""))
                  {
                     if(password.equals(""))
                          onClick(view);
                     else
                     {
                       lblResult.setText("Wrong password");
                     }

                   } else {
                      lblResult.setText("Username does not exist. Please register.");
                   }*/

               } 

           });




      }

     /* public void onClick(View v)
      {

        if (v.getId() == R.id.btnLogin) 
        {
            Intent intent = new Intent(this, CreateVoterSuccess.class);
            startActivity(intent);
        } 
        else
        {
            Intent intent = new Intent(this, HomeActivity.class);
            startActivity(intent);
        }


}*/





class CheckVoter extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(HomeActivity.this);
        pDialog.setMessage("Verifying Voter. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();


    }

    /**
     * getting All products from url
     * */
    protected String doInBackground(String... args) 
    {
        String loginId = getUserId.getText().toString();
        String pwd = getPassword.getText().toString();

        List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("loginId", loginId));
        params.add(new BasicNameValuePair("pwd", pwd));
       // params.add(new BasicNameValuePair("description", description));

        // getting JSON Object
        // Note that create product url accepts POST method
        JSONObject json = jsonParser.makeHttpRequest(url_check_voter,
                "POST", params);
        Log.d("Create Response", json.toString());
        // Building Parameters
        //List<NameValuePair> params = new ArrayList<NameValuePair>();

        // Building Parameters

        // getting JSON string from URL
        //JSONObject json = jsonParser.makeHttpRequest(url_check_voter, "GET", params);
       // Log.d("All Products: ", json.toString());


        try {
            int success = json.getInt(TAG_SUCCESS);
            if (success == 1) 
            {
                Intent i = new Intent(getApplicationContext(), LoginActivity.class);
                startActivity(i);   

            }else if(success == 2)
            {
                //Intent i = new Intent(getApplicationContext(), LoginFail.class);
              //  startActivity(i);

                alertDialogBuilder = new AlertDialog.Builder(
                        HomeActivity.this);
                    // set title
                    alertDialogBuilder.setTitle("Incorrect user name or password");

                    // set dialog message
                    alertDialogBuilder
                        .setMessage("click ohk to enter username or password")
                        .setCancelable(false)
                        .setPositiveButton("OK",new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,int id) {
                                // if this button is clicked, close
                                // current activity
                                HomeActivity.this.finish();
                            }
                          });

                    AlertDialog alert = alertDialogBuilder.create();

            }
            else
            {
                //Intent i = new Intent(getApplicationContext(), CreateVoterFail.class);
              //  startActivity(i);

                alertDialogBuilder = new AlertDialog.Builder(
                        HomeActivity.this);
                    // set title
                    alertDialogBuilder.setTitle("Incorrect user name or password");

                    // set dialog message
                    alertDialogBuilder
                        .setMessage("click ohk to enter username or password")
                        .setCancelable(false)
                        .setPositiveButton("OK",new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,int id) {
                                // if this button is clicked, close
                                // current activity
                                HomeActivity.this.finish();
                            }
                          });
                    AlertDialog alert = alertDialogBuilder.create();

            }
            }catch (JSONException e) {
                e.printStackTrace();
            }
        return null;
     }
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once done
        pDialog.dismiss();
    }

}
}  

并在此处插入警告框...

else 
            {
                //Intent i = new Intent(getApplicationContext(), LoginFail.class);
              //  startActivity(i);

                alertDialogBuilder = new AlertDialog.Builder(
                        HomeActivity.this);
                    // set title
                    alertDialogBuilder.setTitle("Incorrect user name or password");

                    // set dialog message
                    alertDialogBuilder
                        .setMessage("click ohk to enter username or password")
                        .setCancelable(false)
                        .setPositiveButton("OK",new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,int id) {
                                // if this button is clicked, close
                                // current activity
                                HomeActivity.this.finish();
                            }
                          });

                    AlertDialog alert = alertDialogBuilder.create();

            }

我得到运行时错误日志cat如下

09-29 09:54:56.853: D/Create Response(279): {"message":"Product successfully created.","success":0}
09-29 09:54:56.853: W/dalvikvm(279): threadid=7: thread exiting with uncaught exception (group=0x4001d800)
09-29 09:54:56.983: D/dalvikvm(279): GC_FOR_MALLOC freed 2836 objects / 170040 bytes in 118ms
09-29 09:54:56.983: E/AndroidRuntime(279): FATAL EXCEPTION: AsyncTask #1
09-29 09:54:56.983: E/AndroidRuntime(279): java.lang.RuntimeException: An error occured while executing doInBackground()
09-29 09:54:56.983: E/AndroidRuntime(279):  at android.os.AsyncTask$3.done(AsyncTask.java:200)
09-29 09:54:56.983: E/AndroidRuntime(279):  at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
09-29 09:54:56.983: E/AndroidRuntime(279):  at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
09-29 09:54:56.983: E/AndroidRuntime(279):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
09-29 09:54:56.983: E/AndroidRuntime(279):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
09-29 09:54:56.983: E/AndroidRuntime(279):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
09-29 09:54:56.983: E/AndroidRuntime(279):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
09-29 09:54:56.983: E/AndroidRuntime(279):  at java.lang.Thread.run(Thread.java:1096)
09-29 09:54:56.983: E/AndroidRuntime(279): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
09-29 09:54:56.983: E/AndroidRuntime(279):  at android.os.Handler.<init>(Handler.java:121)
09-29 09:54:56.983: E/AndroidRuntime(279):  at android.app.Dialog.<init>(Dialog.java:101)
09-29 09:54:56.983: E/AndroidRuntime(279):  at android.app.AlertDialog.<init>(AlertDialog.java:63)
09-29 09:54:56.983: E/AndroidRuntime(279):  at android.app.AlertDialog.<init>(AlertDialog.java:59)
09-29 09:54:56.983: E/AndroidRuntime(279):  at android.app.AlertDialog$Builder.create(AlertDialog.java:786)
09-29 09:54:56.983: E/AndroidRuntime(279):  at android.app.AlertDialog$Builder.show(AlertDialog.java:801)
09-29 09:54:56.983: E/AndroidRuntime(279):  at com.example.evoting.HomeActivity$CheckVoter.doInBackground(HomeActivity.java:220)
09-29 09:54:56.983: E/AndroidRuntime(279):  at com.example.evoting.HomeActivity$CheckVoter.doInBackground(HomeActivity.java:1)
09-29 09:54:56.983: E/AndroidRuntime(279):  at android.os.AsyncTask$2.call(AsyncTask.java:185)
09-29 09:54:56.983: E/AndroidRuntime(279):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
09-29 09:54:56.983: E/AndroidRuntime(279):  ... 4 more
09-29 09:54:57.793: E/WindowManager(279): Activity com.example.evoting.HomeActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@44f00418 that was originally added here
09-29 09:54:57.793: E/WindowManager(279): android.view.WindowLeaked: Activity com.example.evoting.HomeActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@44f00418 that was originally added here
09-29 09:54:57.793: E/WindowManager(279):   at android.view.ViewRoot.<init>(ViewRoot.java:247)
09-29 09:54:57.793: E/WindowManager(279):   at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
09-29 09:54:57.793: E/WindowManager(279):   at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
09-29 09:54:57.793: E/WindowManager(279):   at android.view.Window$LocalWindowManager.addView(Window.java:424)
09-29 09:54:57.793: E/WindowManager(279):   at android.app.Dialog.show(Dialog.java:241)
09-29 09:54:57.793: E/WindowManager(279):   at com.example.evoting.HomeActivity$CheckVoter.onPreExecute(HomeActivity.java:134)
09-29 09:54:57.793: E/WindowManager(279):   at android.os.AsyncTask.execute(AsyncTask.java:391)
09-29 09:54:57.793: E/WindowManager(279):   at com.example.evoting.HomeActivity$2.onClick(HomeActivity.java:74)
09-29 09:54:57.793: E/WindowManager(279):   at android.view.View.performClick(View.java:2408)
09-29 09:54:57.793: E/WindowManager(279):   at android.view.View$PerformClick.run(View.java:8816)
09-29 09:54:57.793: E/WindowManager(279):   at android.os.Handler.handleCallback(Handler.java:587)
09-29 09:54:57.793: E/WindowManager(279):   at android.os.Handler.dispatchMessage(Handler.java:92)
09-29 09:54:57.793: E/WindowManager(279):   at android.os.Looper.loop(Looper.java:123)
09-29 09:54:57.793: E/WindowManager(279):   at android.app.ActivityThread.main(ActivityThread.java:4627)
09-29 09:54:57.793: E/WindowManager(279):   at java.lang.reflect.Method.invokeNative(Native Method)
09-29 09:54:57.793: E/WindowManager(279):   at java.lang.reflect.Method.invoke(Method.java:521)
09-29 09:54:57.793: E/WindowManager(279):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-29 09:54:57.793: E/WindowManager(279):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-29 09:54:57.793: E/WindowManager(279):   at dalvik.system.NativeStart.main(Native Method)
09-29 09:54:59.273: I/Process(279): Sending signal. PID: 279 SIG: 9
09-29 09:56:18.005: D/Create Response(313): {"message":"Product successfully created.","success":0}
09-29 09:56:18.013: W/dalvikvm(313): threadid=7: thread exiting with uncaught exception (group=0x4001d800)
09-29 09:56:18.153: D/dalvikvm(313): GC_FOR_MALLOC freed 2867 objects / 171224 bytes in 123ms
09-29 09:56:18.153: E/AndroidRuntime(313): FATAL EXCEPTION: AsyncTask #1
09-29 09:56:18.153: E/AndroidRuntime(313): java.lang.RuntimeException: An error occured while executing doInBackground()
09-29 09:56:18.153: E/AndroidRuntime(313):  at android.os.AsyncTask$3.done(AsyncTask.java:200)
09-29 09:56:18.153: E/AndroidRuntime(313):  at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
09-29 09:56:18.153: E/AndroidRuntime(313):  at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
09-29 09:56:18.153: E/AndroidRuntime(313):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
09-29 09:56:18.153: E/AndroidRuntime(313):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
09-29 09:56:18.153: E/AndroidRuntime(313):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
09-29 09:56:18.153: E/AndroidRuntime(313):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
09-29 09:56:18.153: E/AndroidRuntime(313):  at java.lang.Thread.run(Thread.java:1096)
09-29 09:56:18.153: E/AndroidRuntime(313): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
09-29 09:56:18.153: E/AndroidRuntime(313):  at android.os.Handler.<init>(Handler.java:121)
09-29 09:56:18.153: E/AndroidRuntime(313):  at android.app.Dialog.<init>(Dialog.java:101)
09-29 09:56:18.153: E/AndroidRuntime(313):  at android.app.AlertDialog.<init>(AlertDialog.java:63)
09-29 09:56:18.153: E/AndroidRuntime(313):  at android.app.AlertDialog.<init>(AlertDialog.java:59)
09-29 09:56:18.153: E/AndroidRuntime(313):  at android.app.AlertDialog$Builder.create(AlertDialog.java:786)
09-29 09:56:18.153: E/AndroidRuntime(313):  at com.example.evoting.HomeActivity$CheckVoter.doInBackground(HomeActivity.java:220)
09-29 09:56:18.153: E/AndroidRuntime(313):  at com.example.evoting.HomeActivity$CheckVoter.doInBackground(HomeActivity.java:1)
09-29 09:56:18.153: E/AndroidRuntime(313):  at android.os.AsyncTask$2.call(AsyncTask.java:185)
09-29 09:56:18.153: E/AndroidRuntime(313):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
09-29 09:56:18.153: E/AndroidRuntime(313):  ... 4 more
09-29 09:56:18.994: E/WindowManager(313): Activity com.example.evoting.HomeActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@44f00510 that was originally added here
09-29 09:56:18.994: E/WindowManager(313): android.view.WindowLeaked: Activity com.example.evoting.HomeActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@44f00510 that was originally added here
09-29 09:56:18.994: E/WindowManager(313):   at android.view.ViewRoot.<init>(ViewRoot.java:247)
09-29 09:56:18.994: E/WindowManager(313):   at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
09-29 09:56:18.994: E/WindowManager(313):   at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
09-29 09:56:18.994: E/WindowManager(313):   at android.view.Window$LocalWindowManager.addView(Window.java:424)
09-29 09:56:18.994: E/WindowManager(313):   at android.app.Dialog.show(Dialog.java:241)
09-29 09:56:18.994: E/WindowManager(313):   at com.example.evoting.HomeActivity$CheckVoter.onPreExecute(HomeActivity.java:134)
09-29 09:56:18.994: E/WindowManager(313):   at android.os.AsyncTask.execute(AsyncTask.java:391)
09-29 09:56:18.994: E/WindowManager(313):   at com.example.evoting.HomeActivity$2.onClick(HomeActivity.java:74)
09-29 09:56:18.994: E/WindowManager(313):   at android.view.View.performClick(View.java:2408)
09-29 09:56:18.994: E/WindowManager(313):   at android.view.View$PerformClick.run(View.java:8816)
09-29 09:56:18.994: E/WindowManager(313):   at android.os.Handler.handleCallback(Handler.java:587)
09-29 09:56:18.994: E/WindowManager(313):   at android.os.Handler.dispatchMessage(Handler.java:92)
09-29 09:56:18.994: E/WindowManager(313):   at android.os.Looper.loop(Looper.java:123)
09-29 09:56:18.994: E/WindowManager(313):   at android.app.ActivityThread.main(ActivityThread.java:4627)
09-29 09:56:18.994: E/WindowManager(313):   at java.lang.reflect.Method.invokeNative(Native Method)
09-29 09:56:18.994: E/WindowManager(313):   at java.lang.reflect.Method.invoke(Method.java:521)
09-29 09:56:18.994: E/WindowManager(313):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-29 09:56:18.994: E/WindowManager(313):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-29 09:56:18.994: E/WindowManager(313):   at dalvik.system.NativeStart.main(Native Method)
09-29 09:56:48.843: I/Process(313): Sending signal. PID: 313 SIG: 9
09-29 10:09:07.483: D/Create Response(338): {"message":"Product successfully created.","success":0}
09-29 10:09:07.483: W/dalvikvm(338): threadid=7: thread exiting with uncaught exception (group=0x4001d800)
09-29 10:09:07.523: D/dalvikvm(338): GC_FOR_MALLOC freed 2883 objects / 171944 bytes in 41ms
09-29 10:09:07.533: E/AndroidRuntime(338): FATAL EXCEPTION: AsyncTask #1
09-29 10:09:07.533: E/AndroidRuntime(338): java.lang.RuntimeException: An error occured while executing doInBackground()
09-29 10:09:07.533: E/AndroidRuntime(338):  at android.os.AsyncTask$3.done(AsyncTask.java:200)
09-29 10:09:07.533: E/AndroidRuntime(338):  at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
09-29 10:09:07.533: E/AndroidRuntime(338):  at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
09-29 10:09:07.533: E/AndroidRuntime(338):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
09-29 10:09:07.533: E/AndroidRuntime(338):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
09-29 10:09:07.533: E/AndroidRuntime(338):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
09-29 10:09:07.533: E/AndroidRuntime(338):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
09-29 10:09:07.533: E/AndroidRuntime(338):  at java.lang.Thread.run(Thread.java:1096)
09-29 10:09:07.533: E/AndroidRuntime(338): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
09-29 10:09:07.533: E/AndroidRuntime(338):  at android.os.Handler.<init>(Handler.java:121)
09-29 10:09:07.533: E/AndroidRuntime(338):  at android.app.Dialog.<init>(Dialog.java:101)
09-29 10:09:07.533: E/AndroidRuntime(338):  at android.app.AlertDialog.<init>(AlertDialog.java:63)
09-29 10:09:07.533: E/AndroidRuntime(338):  at android.app.AlertDialog.<init>(AlertDialog.java:59)
09-29 10:09:07.533: E/AndroidRuntime(338):  at android.app.AlertDialog$Builder.create(AlertDialog.java:786)
09-29 10:09:07.533: E/AndroidRuntime(338):  at com.example.evoting.HomeActivity$CheckVoter.doInBackground(HomeActivity.java:220)
09-29 10:09:07.533: E/AndroidRuntime(338):  at com.example.evoting.HomeActivity$CheckVoter.doInBackground(HomeActivity.java:1)
09-29 10:09:07.533: E/AndroidRuntime(338):  at android.os.AsyncTask$2.call(AsyncTask.java:185)
09-29 10:09:07.533: E/AndroidRuntime(338):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
09-29 10:09:07.533: E/AndroidRuntime(338):  ... 4 more
09-29 10:09:08.153: E/WindowManager(338): Activity com.example.evoting.HomeActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@44f003e0 that was originally added here
09-29 10:09:08.153: E/WindowManager(338): android.view.WindowLeaked: Activity com.example.evoting.HomeActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@44f003e0 that was originally added here
09-29 10:09:08.153: E/WindowManager(338):   at android.view.ViewRoot.<init>(ViewRoot.java:247)
09-29 10:09:08.153: E/WindowManager(338):   at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
09-29 10:09:08.153: E/WindowManager(338):   at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
09-29 10:09:08.153: E/WindowManager(338):   at android.view.Window$LocalWindowManager.addView(Window.java:424)
09-29 10:09:08.153: E/WindowManager(338):   at android.app.Dialog.show(Dialog.java:241)
09-29 10:09:08.153: E/WindowManager(338):   at com.example.evoting.HomeActivity$CheckVoter.onPreExecute(HomeActivity.java:134)
09-29 10:09:08.153: E/WindowManager(338):   at android.os.AsyncTask.execute(AsyncTask.java:391)
09-29 10:09:08.153: E/WindowManager(338):   at com.example.evoting.HomeActivity$2.onClick(HomeActivity.java:74)
09-29 10:09:08.153: E/WindowManager(338):   at android.view.View.performClick(View.java:2408)
09-29 10:09:08.153: E/WindowManager(338):   at android.view.View$PerformClick.run(View.java:8816)
09-29 10:09:08.153: E/WindowManager(338):   at android.os.Handler.handleCallback(Handler.java:587)
09-29 10:09:08.153: E/WindowManager(338):   at android.os.Handler.dispatchMessage(Handler.java:92)
09-29 10:09:08.153: E/WindowManager(338):   at android.os.Looper.loop(Looper.java:123)
09-29 10:09:08.153: E/WindowManager(338):   at android.app.ActivityThread.main(ActivityThread.java:4627)
09-29 10:09:08.153: E/WindowManager(338):   at java.lang.reflect.Method.invokeNative(Native Method)
09-29 10:09:08.153: E/WindowManager(338):   at java.lang.reflect.Method.invoke(Method.java:521)
09-29 10:09:08.153: E/WindowManager(338):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-29 10:09:08.153: E/WindowManager(338):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-29 10:09:08.153: E/WindowManager(338):   at dalvik.system.NativeStart.main(Native Method)

Answer 1

doInBackground 在后台线程上工作，因此您将无法在此方法中更新 UI。

如果您希望为用户更新 UI，您需要在 ASyncTask 中实现 onPostExecute 以显示 Dialog(或类似的东西)以在发生错误时通知用户。

您可以在任何线程中使用此 block 来更新 UI 内容。

Runnable run_in_ui = new Runnable() {
    @Override
    public void run() {
        // do your UI stuffs here
    }
};
runOnUiThread(run_in_ui);