Having trouble building an API request with retrofit?

Question

Java

Having trouble building an API request with retrofit?
This is what the API class looks like:

public class API
{
    private static final String SOURCE = "http://moonwalk.cc/api";
    private final CinemaService mService;
    String api_token="тут токен";

    final String TAG = "myLogs";
    Context ctx;

    ArrayList<Cinema> cinemas = new ArrayList<Cinema>();

    public interface CinemaService {
        @GET("/serial_updates.json")
        Call<CinemaData> getCinemas(@Query("api_token") String api_token);
    }

    public interface APIS
    {
        public void getData();
    }
    APIS apis;

    public API(Context ctx) {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(SOURCE)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        mService = retrofit.create(CinemaService.class);
        try {
            apis = (APIS) ctx;
        } catch (ClassCastException e) {
            throw new ClassCastException(ctx.toString()
                    + " must implement onSomeEventListener");
        }

        this.ctx = ctx;
    }

    public boolean getCinema(final int numCat, final String title, final int kinopoisk_id)
    {
        mService.getCinemas(api_token).enqueue(new Callback<CinemaData>() {
            @Override
            public void onResponse(Response<CinemaData> response, Retrofit retrofit) {
                //cinemas.add(new Cinema(response.body().responseData.current_page));
                Log.d("myLogs", "s="+response.body().responseData.serial);
                apis.getData();
            }

            @Override
            public void onFailure(Throwable t) {
                Log.d("myLogs", "Failed!!!");
            }
        });
        return true;
    }
}

class CinemaData {
    ResponseData responseData;
}

class ResponseData {
    String serial;

Request is made to this address:

http://moonwalk.cc/api/serials_updates.json?api_token=тут токен

json output looks like this:

{"current_page":1,"updates":[{"added_at":"2016-02-22 19:12:17","token":"222db177654acd99","episode_iframe_url":"http://moonwalk.cc/serial/d3e8cd59ad3790aa5ff2393058014e1a/iframe?episode=4\u0026season=1","video_iframe_url":"http://moonwalk.cc/video/222db177654acd99/iframe","serial":{"title_ru":"Путь к выздоровлению","title_en":"Recovery Road","token":"d3e8cd59ad3790aa5ff2393058014e1a","type":"serial","kinopoisk_id":891572,"translator":"HamsterStudio ","translator_id":8,"iframe_url":"http://moonwalk.cc/serial/d3e8cd59ad3790aa5ff2393058014e1a/iframe","seasons_count":1,"episodes_count":4,"category":null}},{"added_at":"2016-02-22 18:34:50","token":"59ad4ac760fd5f52","episode_iframe_url":"http://moonwalk.cc/serial/befca8d16d813d73aab573ea39545be3/iframe?episode=7\u0026season=1","video_iframe_url":"http://moonwalk.cc/video/59ad4ac760fd5f52/iframe","serial":{"title_ru":"Отвечай-ка, наша Галко!","title_en":"Oshiete! Galko-chan","token":"befca8d16d813d73aab573ea39545be3","type":"serial","kinopoisk_id":null,"translator":"AniDUB","translator_id":49,"iframe_url":"http://moonwalk.cc/serial/befca8d16d813d73aab573ea39545be3/iframe","seasons_count":1,"episodes_count":7,"category":"anime"}},

How to get the data of the "title_ru" field from such an output, as I understand it, before that, you need to get the data of the "serial" field?!
The given code throws an error:

java.lang.NullPointerException: Attempt to read from field 'net.kinomovies.onlinemovielibrary.ResponseData net.kinomovies.onlinemovielibrary.CinemaData.responseData' on a null object reference

Answer 1

Smoking what is GSON and how to work with it. There is no magic there. GSON looks in your response for the key responseData and doesn't find it, so responseData = null. Annotations must be correct. And your json doesn't match the structure you want to parse at all. Think about it.
And you, I see, do not learn anything, in the last question I gave you advice - and you did not follow them, post all the same shit-copy-paste. In vain.

Answer 2

Here is an excellent tutorial in Russian and Kotlin on how to work with GSON and Retrofit androidschool.ru/courses/android-retrofit-and-gson