request json data with volley

RequestVolley.java

private void getDataRequest() {
        String url= "";
        RequestQueue queue = Volley.newRequestQueue(getActivity());
        StringRequest postRequest = new StringRequest(Request.Method.GET, url,
                new Response.Listener<String>()
                {
                    @Override
                    public void onResponse(String response) {
                        progress.dismiss();
                        Log.d("response", response);
                        try {
                            Gson gson = new GsonBuilder().registerTypeAdapterFactory(new ArrayAdapterFactory()).create();
                            ResultJson dataResult = gson.fromJson(response, ResultJson.class);

                            modelSurvey = dataResult.getSurvey();
                            Adapter adapter = new Adapter(
                                    getContext(), modelSurvey);
                            lvSurvey = (ListView)getActivity().findViewById(R.id.lvSurvey);

                            lvSurvey.setAdapter(adapter);

                            lvSurvey.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                                @Override
                                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                                    //task when clicked
                                }
                            });

                        }catch (Exception e){
                            Log.d("error todolist", Log.getStackTraceString(e));
                            Toast.makeText(getActivity(), "Error load data", Toast.LENGTH_SHORT).show();
                        }
                    }
                },
                new Response.ErrorListener()
                {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        progress.dismiss();
                        Log.d("ERROR", "error => " + error.toString());
                        Toast.makeText(getActivity(), "Error", Toast.LENGTH_SHORT).show();
                    }
                }
        ) {
            @Override
            public Map<String, String> getHeaders() throws AuthFailureError {
                Map<String, String>  params = new HashMap<String, String>();
                params.put("key", "value");
                return params;
            }
        };
        queue.add(postRequest);
    }