How to parse JSON using Retrofit correctly and implement it in RecyclerView? - mvvm

Question

I'm trying to build an app that has 2 tabs that displays Movies and TV Shows using the themoviedb.org API. It's supposed to use the MVVM model and i'm really confuse because it's just been 2 months since i started coding in Android. How to pass it correctly through each class and do i using the retrofit method correctly in the repository class?
The idea is accessing the API through Repository class and pass the data to the ViewModel class, and then display it in MovieFragment using RecyclerView, but it seems i failed to pass the data through each class.
+MovieRepository Class
public class MovieRepository {
private static MovieRepository instance;
private static ArrayList<Movie> movies = new ArrayList<>();
private final String API_KEY = "81d8f4353c2ade529071133972205017";
private String language;
private final String TAG = "repo";
public static MovieRepository getInstance() {
if (instance == null) {
instance = new MovieRepository();
}
return instance;
}
public static ArrayList<Movie> getMovies() {
return movies;
}
public MovieRepository() {
final ArrayList<Movie> movieJSON = new ArrayList<>();
language = "en_US";
ApiConfig api = new ApiConfig();
api.createInstance().loadMovieData(API_KEY, language).enqueue(new Callback<JSONResponse>() {
#Override
public void onResponse(Call<JSONResponse> call, Response<JSONResponse> response) {
ArrayList<Movie> jsonResults = response.body().getResults();
for (int i = 0; i < jsonResults.size() ; i++){
Movie movie = new Movie();
movie.setId(jsonResults.get(i).getId());
movie.setTitle(jsonResults.get(i).getTitle());
movie.setOverview(jsonResults.get(i).getOverview());
movie.setReleaseDate(jsonResults.get(i).getReleaseDate());
movie.setPosterPath(jsonResults.get(i).getPosterPath());
movieJSON.add(movie);
}
Log.d(TAG, "onResponse: " + jsonResults.toString());
}
#Override
public void onFailure(Call<JSONResponse> call, Throwable t) {
Log.d(TAG, "onFailure: " + t.getMessage());
}
});
this.movies = movieJSON;
}
+MovieViewModel Class
public class MovieViewModel extends ViewModel {
private static MutableLiveData<ArrayList<Movie>> movieData = new MutableLiveData<>();
private static ArrayList<Movie> movies;
public static LiveData<ArrayList<Movie>> getMoviesData() {
return movieData;
}
public static MovieAdapter init(MovieAdapter adapter) {
if (movies == null) {
movies = MovieRepository.getInstance().getMovies();
adapter.setMovies(movies);
}
return adapter;
}
+MovieFragment Class
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
movieViewModel = ViewModelProviders.of(this).get(MovieViewModel.class);
adapter = new MovieAdapter(getContext());
movieViewModel.init(adapter);
movieViewModel.getMoviesData().observe(this, new Observer<ArrayList<Movie>>() {
#Override
public void onChanged(#Nullable ArrayList<Movie> movies) {
adapter.notifyDataSetChanged();
}
});
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_movie_list, container, false);
if (view instanceof RecyclerView) {
final Context context = view.getContext();
RecyclerView recyclerView = (RecyclerView) view;
recyclerView.setLayoutManager(new LinearLayoutManager(context));
recyclerView.setAdapter(adapter);
}
return view;
}
it always ends up NullPointer in the Adapter (probably because the data failed to be passed to adapter)