Trying to change TextView text inside asynctask

Question

I would like to change the text from a TextView when a JSON array is empty.

This is the code where I am getting the JSON array:

private void getEntrenadoresFromDB(int id) {

        AsyncTask<Integer, Void, Void> asyncTask = new AsyncTask<Integer, Void, Void>() {
            @Override
            protected Void doInBackground(Integer... entrenadoresIds) {
                Log.d("CEF", "WORKOUT SELECCIONADO: " + workout_seleccionado);
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder()
                        .url("http://....php?id=" + workout_seleccionado)
                        .build();
                try {
                    okhttp3.Response response = client.newCall(request).execute();

                    JSONArray array = new JSONArray(response.body().string());





                    for (int i = 0; i < array.length(); i++) {
                        int numeroentrenadores = array.length();
                        Log.d("HOLA PERFIL", "NUMERO ENTRENADORES: " + numeroentrenadores);
                        Log.d("HOLA PERFIL", "NUMERO ENTRENADORES: " + numeroentrenadores);
                        JSONObject object = array.getJSONObject(i);
                        Log.d("HOLA ENTRENADORES", "ENTRENADOR LEIDO: " + object.getString("imagen_art"));
                        Entrenador entrenador = new Entrenador(object.getInt("id_entrenador"), object.getString("corto"),object.getString("largo"),
                                object.getInt("sexo"),object.getString("ciudad"), object.getString("imagen_art"),
                                object.getString("nombre_art"),object.getString("usuario"), object.getInt("workout"), object.getDouble("latitud_entrenador"), object.getDouble("longitud_entrenador"));
                        entrenadores.add(entrenador);
                    }


                } catch (IOException e) {
                    e.printStackTrace();
                    Log.d("HOLA PERFIL", "NUMERO ENTRENADORES: " +"no hay entrenadores io exception");
                } catch (JSONException e) {
                    e.printStackTrace();
                    Log.d("HOLA PERFIL", "NUMERO ENTRENADORES: " +"no hay entrenadores json exception");
                    txtNo.setText("h");

                }
                return null;
            }

            @Override
            protected void onPostExecute(Void aVoid) {
                adapter.notifyDataSetChanged();
            }
        };

        asyncTask.execute(id);
    }

As you may see, I have tried putting it under catch (JSONException e), but there is a warning: setText must be called from the UI thread... What should I do?

Possible duplicate of [Method setText must be called from the UI thread](https://stackoverflow.com/questions/43924166/method-settext-must-be-called-from-the-ui-thread) — Bertram Gilfoyle, Jun 18 '17 at 08:21
@AhamadAnees, the question is not to do it under the asyctask, the question is about to know when the JSON array is empty — mvasco, Jun 18 '17 at 08:23
you are already checking the size of array. and changing ui elements from non ui thread is error but not warning and for which people have alreadt responded. What exactly is the issue again? — Mohammed Atif, Jun 18 '17 at 08:29
@MohammedAtif, if the array, then is empty int numeroentrenadores = array.length(); is not executed. — mvasco, Jun 18 '17 at 08:30
obviously right, that line is inside for loop, if your length is 0, for loop wont loop at all. — Mohammed Atif, Jun 18 '17 at 08:31

Darish · Accepted Answer · 2017-06-18T10:07:19.290

1

but there is a warning: setText must be called from the UI thread... What should I do?

Yes, the setText method should be called from the UI thread. So you can call it from onPostExecute(Void aVoid) instead of doInBackground(Integer... entrenadoresIds). Make the doInBackGround method return the array size so that you can compare the value in the onPostExecute(Integer result)

if(array!=null && array.length()>0){
   //do your stuff here
   return array.length();
}
return 0;

edited Jun 18 '17 at 10:07

answered Jun 18 '17 at 08:23

Darish

11,032
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Thank you, but I need to know when the array is empty – mvasco Jun 18 '17 at 08:24
@mvasco it's dead simple. make the doInBackground method return array size instead of null when the json Array is not empty. So you can compare it later in the onPostExecute right? :) – Darish Jun 18 '17 at 08:27
I would like to implement your answer, but I don´t know how to return array size instead of null. – mvasco Jun 18 '17 at 09:34

p_0g_amm3_ · Answer 2 · 2017-06-18T08:28:54.853

1

You cannot call Ui related things from doInBackground, they have to be called in onPreExecute or in onPostExecute. If you want to change the text if it failed, change the returntype of doInBackground from void to boolean and return false, if it was successful and true if it failed. Then, in onPostExecute check if it failed or not and set the text accordingly. If you want distinguish between different errors, use String instead of boolean.

edited Jun 18 '17 at 08:28

answered Jun 18 '17 at 08:27

p_0g_amm3_

451
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Thank you, but I need to know if the JSON array is empty. – mvasco Jun 18 '17 at 08:28
You can also check that at the end of doInBackground and return true if it's empty – p_0g_amm3_ Jun 18 '17 at 08:38

Vyacheslav · Answer 3 · 2017-06-18T08:43:51.643

0

Change your code by this:

JSONArray array = new JSONArray(response.body().string());

if (array.length() == 0) {
    runOnUiThread(new Runnable() {
                   @Override
                   public void run() {
                      textView.setText("your message");       
                   }
                });
}

EDIT

note: runOnUiThread is a method of Activity class

edited Jun 18 '17 at 08:43

answered Jun 18 '17 at 08:24

Vyacheslav

26,359
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@mvasco getEntrenadoresFromDB - where this method is placed? – Vyacheslav Jun 18 '17 at 08:42
Solved, it is a fragment, I have to add getActivity().runOnUiThread – mvasco Jun 18 '17 at 08:43
It is not working, since array is empty your proposal is never called. At least where you say to put it. – mvasco Jun 18 '17 at 08:47
@mvasco post your data you receive – Vyacheslav Jun 18 '17 at 08:48
@mvasco `array.length() == 0` means your array is empty – Vyacheslav Jun 18 '17 at 08:49
yes, but if I put it inside the try loop, if the array is empty, the try loop is not called – mvasco Jun 18 '17 at 08:50
@mvasco what do you mean 'try loop'. It is difficult to understand you – Vyacheslav Jun 18 '17 at 08:53
@mvasco i've shown how to check whether the array is empty and how to set text of the textview – Vyacheslav Jun 18 '17 at 08:54
I know, but I can hardly check for if (array.length() == 0) if it is never called – mvasco Jun 18 '17 at 08:55

Trying to change TextView text inside asynctask

3 Answers3