Android - Wait for volley response for continue

Question

I build an app, that it load markers in a map, the markers I get it for volley JSON file, but I need that first to load volley, and after continue executing the code, because the other way show me error with latLng null, this parameter is not loaded fast, and another method execute first and show me null.

My volley code for load markers

public  void getMarkers(){

    requestQueue = Volley.newRequestQueue(getApplicationContext());
    JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, url, new Response.Listener<JSONObject>() {


        @Override
        public void onResponse(JSONObject response) {

            try {

                JSONArray saagTracker = response.getJSONArray("saagMRK");
                for (int i = 0; i < saagTracker.length(); i++) {
                    JSONObject object = saagTracker.getJSONObject(i);

                    title = object.getString(TITLE);
                    snnipet = object.getString(SNNIP);
                    latLng = new LatLng(Double.parseDouble(object.getString(LAT)), Double.parseDouble(object.getString(LNG)));
                    coor = coor + "|" + object.getString(LAT) + "," + object.getString(LNG);                        // Menambah data marker untuk di tampilkan ke google map

                    addMarker(latLng, title, snnipet);

                }

            } catch (JSONException e) {
                e.printStackTrace();
            }
            //JSONArray array = new JSONArray(response.body().string());

        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Toast.makeText(MainActivity.this, "Ocurrio un error", Toast.LENGTH_LONG).show();
        }
    });
    requestQueue.add(jsonObjectRequest);
}

onCreate it need latLng first for it to can load my geofire parameter

geoQuery = geofire.queryAtLocation(new GeoLocation(latLng.latitude, latLng.longitude),0.1f); // latLng it coming null

Answer 1

You would need to implement a call back for the volley response. A very simple way to do this would be the following.

Step 1: Create this interface

public interface VolleyCallBack {
    void onSuccess();
}

Step 2: change your getMarkers() method to this:

public  void getMarkers(final VolleyCallBack callBack){

requestQueue = Volley.newRequestQueue(getApplicationContext());
JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, url, new Response.Listener<JSONObject>() {


    @Override
    public void onResponse(JSONObject response) {

        try {

            JSONArray saagTracker = response.getJSONArray("saagMRK");
            for (int i = 0; i < saagTracker.length(); i++) {
                JSONObject object = saagTracker.getJSONObject(i);

                title = object.getString(TITLE);
                snnipet = object.getString(SNNIP);
                latLng = new LatLng(Double.parseDouble(object.getString(LAT)), Double.parseDouble(object.getString(LNG)));
                coor = coor + "|" + object.getString(LAT) + "," + object.getString(LNG);                        // Menambah data marker untuk di tampilkan ke google map

                addMarker(latLng, title, snnipet);

                callback.onSuccess();

            }

        } catch (JSONException e) {
            e.printStackTrace();
        }
        //JSONArray array = new JSONArray(response.body().string());

    }
}, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
        Toast.makeText(MainActivity.this, "Ocurrio un error", Toast.LENGTH_LONG).show();
    }
});
requestQueue.add(jsonObjectRequest);
}

Step 3: Call your getMarkers() method like this:

getMarkers(new VolleyCallBack() {

                @Override
                public void onSuccess() {
                    // this is where you will call the geofire, here you have the response from the volley.
                    geoQuery = geofire.queryAtLocation(new GeoLocation(latLng.latitude, latLng.longitude),0.1f);
                });