protected Void doInBackground(Void... params) {
            // Create an array
            arraylist = new ArrayList<HashMap<String, String>>();
            // Retrieve JSON Objects from the given URL address
            jsonobject = JSONfunctions
                    .getJSONfromURL("http://.../android_ofertaslist_todas.php");

            try {
                // Locate the array name in JSON
                jsonarray = jsonobject.getJSONArray("Categorias");

                for (int i = 0; i < jsonarray.length(); i++) {
                    HashMap<String, String> map = new HashMap<String, String>();
                    jsonobject = jsonarray.getJSONObject(i);
                    // Retrive JSON Objects
                    map.put("valoracionEmpresa", jsonobject.getString("valoracionEmpresa"));
                    map.put("nombreEmpresa", jsonobject.getString("nombreEmpresa"));
                    map.put("direccionEmpresa", jsonobject.getString("direccionEmpresa"));
                    map.put("strImagen", jsonobject.getString("strImagen"));//<--- THIS IS THE IMAGE FILE NAME
                    // Set the JSON Objects into the array
                    arraylist.add(map);
                }
            } catch (JSONException e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return null;
        }