GetterAndSetter returns empty ArrayList

Question

I am adding String returned by Callback method from Volley's onRespond method.

I have already initialized GetterAndSetter Method inside OnCreate Method.

this is my code:

onRespond(){
       ...
       AddtoList(CreateURL, new VolleyCallback() {
                @Override
                public void onSuccess(String result) {
                    getterAndSetter.addString(result);
                }
            });
       ....
}

My GetterAndSetter Class:

public class GetterAndSetter {
    ArrayList<String> strings = new ArrayList<>();

    public void addString(String string) {
        this.strings.add(string);
    }

    public ArrayList<String> getList(){
        return this.strings;
    }
}

I tries to get all the strings added inside of this getterandsetter's ArrayList via following code inside my another method :

void LoadImages(MainActivity mainActivity){
       ...
        List<String> details = getterAndSetter.getList();
        Log.d("gs", getterAndSetter.getList().toString());
       ...
}

As seen above, I tried to print log, but it print "[]"(Empty String). I have seen alot of Answers on Stackoverflow, but can't solve my problem.

Update : I am adding more code so that you guys can understand the problem.

My OnCreate Method :

 @Override
protected void onCreate(Bundle savedInstanceState) {
    ...
    getterAndSetter = new GetterAndSetter();
    LoadImages(this);
}

LoadImages :

private void LoadImages(MainActivity mainActivity) {
            StringRequest stringRequest = new StringRequest(URL, new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {

                    mView.dismiss();

                    Log.d("Respone", "onResponse: " + response);

                    //  Used to Get List of Images URLs
                    getResponse = ParseJSON(response);

                    List<String> urlList = getResponse.get(0);
                    List<String> titles = getResponse.get(1);
                    List<String> details = getterAndSetter.getList();

                    Log.d("gs", getterAndSetter.getList().toString());

                    for (String urls : urlList) {
                        Log.d("urls", urls);
                    }

                    for (String title : titles) {
                        Log.d("tts", title);
                    }

                    for (String dt : details) {
                        Log.d("dts", dt);
                    }


                }
            }, error -> {
                Log.d(TAG, "onErrorResponse: Error Occured...");
            });
            RequestQueue requestQueue = Volley.newRequestQueue(this);
            requestQueue.add(stringRequest);
    }

ParseJSON method :

ArrayList<ArrayList<String>> ParseJSON(String URL) {
        try {
            JSONObject root = new JSONObject(URL);
            JSONObject photos = root.getJSONObject("photos");
            JSONArray photo = photos.getJSONArray("photo");

            ArrayList<String> listURLS = new ArrayList<>();
            ArrayList<String> Titles = new ArrayList<>();

            ArrayList<ArrayList<String>> result = new ArrayList<>();

            for (int i = 0; i < photo.length(); i++) {
                JSONObject photosJSONObject = photo.getJSONObject(i);
                String FarmID = photosJSONObject.getString("farm");
                String ServerID = photosJSONObject.getString("server");
                String ID = photosJSONObject.getString("id");
                String SecretID = photosJSONObject.getString("secret");
                String ImageTitle = photosJSONObject.getString("title");

                listURLS.add(i, CreatePhotoURL(FarmID, ServerID, ID, SecretID));
                Titles.add(i, ImageTitle);

                String CreateURL = "https://api.flickr.com/services/rest/?method=flickr.photos.getInfo&api_key=" + API_Key + "&photo_id=" + ID + "&format=json&nojsoncallback=1";

                AddtoList(CreateURL, new VolleyCallback() {
                    @Override
                    public void onSuccess(String result) {
                        getterAndSetter.addString(result);
                    }
                });

                result.add(listURLS);
                result.add(Titles);
            }
            return result;
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return null;
    }

AddtoList Method :

public void AddtoList(String CreateURL, VolleyCallback volleyCallback) {
        RequestQueue requestQueue = Volley.newRequestQueue(this);

        StringRequest stringRequest = new StringRequest(CreateURL, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                JSONObject root;
                try {
                    root = new JSONObject(response);
                    JSONObject photo = root.getJSONObject("photo");

                    String username = photo.getJSONObject("owner").getString("username");
                    String DateTaken = photo.getJSONObject("dates").getString("taken");
                    String Views = photo.getString("views");

                    String str = "Date Taken : " + DateTaken + "\n" + "Views : " + Views + "\n" + "User Name : " + username + "\n";

                    volleyCallback.onSuccess(str);
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.d(TAG, "onErrorResponse: " + error.toString());
            }
        });
        requestQueue.add(stringRequest);
    }

My CallBack

public interface VolleyCallback {
        void onSuccess(String result);
    }

you don't add anything to the list, what else do you expect it to return? — Stultuske, Jun 19 '18 at 13:25
Did you put a log in `onSuccess(String result)` method to get the value of result — Yati Sawhney, Jun 19 '18 at 13:25
@AviPatel which is not called in the code you posted, so you are not actually adding values. — Stultuske, Jun 19 '18 at 13:27
@yates, yes i have printed logs and getting strings which are not empty. — Avi Patel, Jun 19 '18 at 13:27
@AviPatel so, the `details` contains the strings, but the `Log.d` does not print anything, correct? — Luca Nicoletti, Jun 19 '18 at 13:28
@Stultuske, I haven't added the code, but it's getting called via volleyCallback.onSuccess(str); method inside of my Volley's onRespond() method — Avi Patel, Jun 19 '18 at 13:28
Put some more code so that we could see what exactly is happening — Yati Sawhney, Jun 19 '18 at 13:28
You should iterate the list: `for (String str : details) Log.d("gs", str);` instead of calling `toString()' of the List-object - independently from your problem. — ChristophS, Jun 19 '18 at 13:28
@LucaNicoletti, No Actually I am Adding the string inside ArrayList, but while getting or adding I am doing some mistake by which i am getting empty list. — Avi Patel, Jun 19 '18 at 13:30
@ChristophS, I have tried it, but it didn't even print logs, because it's empty. — Avi Patel, Jun 19 '18 at 13:30
Shouldn't the parameter of `onSuccess` be of the type `JSONObject`? So calling the toString of this parameter may result in `null`, thus you are adding `null` to your list, so it's empty. — ChristophS, Jun 19 '18 at 13:34
@AviPatel can you post some more code? How do you initialize `getterAndSetter`? The body of `AddtoList` method? — Luca Nicoletti, Jun 19 '18 at 13:35
Where are you calling `foo()`? Be sure you don't call it before getting the response — Alberto Méndez, Jun 19 '18 at 13:39
@AlbertoMéndez, Foo() was my LoadImages Method, it was just to simplification. I have changed it. — Avi Patel, Jun 19 '18 at 13:41
And you don't use `onRespond()` callback as mentioned, you use `onSuccess()` ... — ChristophS, Jun 19 '18 at 13:41
Place your logging inside `addString(String string){}` as last statement. Log `strings` list directly and see if it is growing on each event. — ChristophS, Jun 19 '18 at 13:50
@ChristophS Yes it's growing... I have put Log.d("hi", this.strings.toString()); and it's giving me arraylist as String format and from that i got it. It's adding values 1 by 1 on every iteration.. — Avi Patel, Jun 19 '18 at 13:51

score 0 · Answer 1 · answered Jun 19 '18 at 13:57

0

The problem is that you're trying to print the list BEFORE the callback is being invoked by Volley.

You parse a Json and for each element, you make a new request. After parsing the Json you print the list, it's empty because of the calls you make aren't ended at the moment you print the list.

You need to wait until all the request you start from inside the loop have ended.

answered Jun 19 '18 at 13:57

Luca Nicoletti

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I have a doubt. I am getting Strings via printing logs, inside my getter and setter. If your suggestion is valid then isn't logs inside getterAndSetter empty as well? – Avi Patel Jun 19 '18 at 14:16
No, if you log the values inside the `addString` method, them shouldn't be empty – Luca Nicoletti Jun 19 '18 at 15:00
How can i access them, so that i dont get it Empty? I have also tried making arraylist of URLs and then pass it one by one, which is the same thing. – Avi Patel Jun 19 '18 at 15:12

GetterAndSetter returns empty ArrayList

1 Answers1