Java : Android : Retrofit 2 response code is 200, response.body is null

I am trying to build an Android App that implements a Collaborative Filtering Algorithm using Retrofit 2,Realm and The Movie Database API.
When making my Retrofit callback, onResponse returns a successful status code (200), but from logging I get that my response.body().getResults returns null. I'm in this pickle now and I can't get it to work.My ApiService seem to be working fine and I make other retrofit callbacks to get directors,movies by title,movies by release date.Anyways, here is some code snippets that might be helpful.

APIService.java

package com.yannis.thesis.movierecommendationapp.api;

import com.yannis.thesis.movierecommendationapp.models.DirectorResponse;
import com.yannis.thesis.movierecommendationapp.models.GenreResponse;
import com.yannis.thesis.movierecommendationapp.models.Movie;
import com.yannis.thesis.movierecommendationapp.models.MovieResponse;
import com.yannis.thesis.movierecommendationapp.models.PrimaryMovieInfo;

import retrofit2.Call;
import retrofit2.http.GET;
import retrofit2.http.POST;
import retrofit2.http.Path;
import retrofit2.http.Query;

public interface APIService {

@POST("/list")
Call<Movie> loadMovie();

@GET("movie/top_rated")
Call<MovieResponse> getTopRatedMovies(@Query("api_key") String apiKey);

@GET("movie/popular")
Call<MovieResponse> getPopularMovies(@Query("api_key") String apiKey);

@GET("movie/{id}")
Call<MovieResponse> getMovieDetails(@Path("id") int id, @Query("api_key") String apiKey);

@GET("search/movie")
Call<MovieResponse> getMovieByTitle(@Query("query") String title, @Query("api_key") String apiKey);
}


MovieResponse.java

package com.yannis.thesis.movierecommendationapp.models;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

import java.util.List;

public class MovieResponse {

@SerializedName("page")
private Integer page;
@SerializedName("results")
private List<Movie> results;
@SerializedName("total_results")
private Integer totalResults;
@SerializedName("total_pages")
private Integer totalPages;

public Integer getPage() {
return page;
}

public void setPage(Integer page) {
this.page = page;
}

public List<Movie> getResults() {
return results;
}

public void setResults(List<Movie> results) {
this.results = results;
}

public Integer getTotalResults() {
return totalResults;
}

public void setTotalResults(Integer totalResults) {
this.totalResults = totalResults;
}

public Integer getTotalPages() {
return totalPages;
}

public void setTotalPages(Integer totalPages) {
this.totalPages = totalPages;
}
}


MovieRecommendationApp.java

package com.yannis.thesis.movierecommendationapp;

import android.app.Application;
import android.support.annotation.NonNull;
import android.support.v4.view.PagerAdapter;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;

import com.luseen.logger.LogType;
import com.luseen.logger.Logger;
import com.weiwangcn.betterspinner.library.BetterSpinner;
import com.yannis.thesis.movierecommendationapp.activities.BaseActivity;
import com.yannis.thesis.movierecommendationapp.activities.MainActivity;
import com.yannis.thesis.movierecommendationapp.api.APIService;
import com.yannis.thesis.movierecommendationapp.models.DirectorResponse;
import com.yannis.thesis.movierecommendationapp.models.DirectorResult;
import com.yannis.thesis.movierecommendationapp.models.Genre;
import com.yannis.thesis.movierecommendationapp.models.GenreResponse;
import com.yannis.thesis.movierecommendationapp.models.MainPagerEnum;
import com.yannis.thesis.movierecommendationapp.models.Movie;
import com.yannis.thesis.movierecommendationapp.models.MovieResponse;
import com.yannis.thesis.movierecommendationapp.models.MovieRecommendedForUser;
import com.yannis.thesis.movierecommendationapp.models.Recommendation;
import com.yannis.thesis.movierecommendationapp.models.User;
import com.yannis.thesis.movierecommendationapp.models.UserRatesMovie;
import com.yannis.thesis.movierecommendationapp.MovieRecommendationApp;
import com.yannis.thesis.movierecommendationapp.R;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import butterknife.BindView;
import butterknife.ButterKnife;
import butterknife.OnClick;

import io.realm.Realm;
import io.realm.RealmConfiguration;
import io.realm.RealmQuery;
import io.realm.RealmResults;
import io.realm.Sort;
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.Headers;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.ResponseBody;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MovieRecommendationApp extends Application {

private static MovieRecommendationApp instance;
public BaseActivity lastActivity;

String API_BASE_URL = "http://api.themoviedb.org/3/";
private final static String API_KEY = "******************";
private static Retrofit retrofitinstance;

private String loggedInUserId;
private Realm realm;
final Double SIMILARITY_PILLOW = 0.5;
final Double PREDICTION_PILLOW = 3.0;

private APIService client;
OkHttpClient.Builder httpClient = new OkHttpClient.Builder();


Retrofit.Builder builder =
new Retrofit.Builder()
.baseUrl(API_BASE_URL)
.addConverterFactory(
GsonConverterFactory.create()
);

Retrofit retrofit =
builder
.client(
httpClient.build()
)
.build();

retrofit2.Call<MovieResponse> call;

@Override
public void onCreate() {
super.onCreate();
instance = this;

Realm.init(this);
RealmConfiguration config = new RealmConfiguration.Builder()
.name("myrealmDB.realm")
.deleteRealmIfMigrationNeeded()
.build();
Realm.setDefaultConfiguration(config);

new Logger.Builder()
.isLoggable(BuildConfig.DEBUG)
.logType(LogType.WARN)
.tag("Iamerror")
.build();

realm = Realm.getDefaultInstance();

MovieRecommendationAlgorithm();

}

public static MovieRecommendationApp getInstance() {
return instance;
}

public static Retrofit getRetrofitInstance() {
return retrofitinstance;
}

public static String getApiKey() {
return API_KEY;
}


public void MovieRecommendationAlgorithm() {
prediction("activeUserId","637",neighbours);

}
public void prediction(String activeUserId, String notYetRatedMovieId,ArrayList<String> neightbours) {
Double activeAVG = avgRating(activeUserId);
Double A = 0.0;
Double B = 0.0;
for (int i = 0; i < neightbours.size(); i++) {
avgRating(neightbours.get(i));
A = A + similarity(activeUserId, neightbours.get(i)) * (getUser_i_MovieRating(neightbours.get(i), notYetRatedMovieId) - avgRating(neightbours.get(i)));
B = B + similarity(activeUserId, neightbours.get(i));
}
final Double prediction = activeAVG + A / B;
if (prediction < PREDICTION_PILLOW) {
return;
}
int movieId = Integer.parseInt(notYetRatedMovieId);
client = retrofit.create(APIService.class);
call = client.getMovieDetails(movieId, MovieRecommendationApp.getApiKey());
call.enqueue(new retrofit2.Callback<MovieResponse>() {
@Override
public void onResponse(retrofit2.Call<MovieResponse> call, retrofit2.Response<MovieResponse> response) {
int statusCode = response.code();
if (response.isSuccessful() == false) {
Logger.w("unsuccessful w status", String.valueOf(statusCode));
} else {
//problem is in this spot
Logger.w( " reponse body is " + response.body().getResults());
}

// Logger.e("Number of movies received: " + movies.size());
}

@Override
public void onFailure(retrofit2.Call<MovieResponse> call, Throwable t) {

}
});
}
}


I double checked the API call using Postman - calling https://api.themoviedb.org/3/movie/637?api_key=*********&language=en-US
got me the desired JSON Body.
Thank you for you time and help.

https://api.themoviedb.org/3/movie/637?api_key=*********&language=en-US

url

2 Answers
2

I don't know if this will be helpfull, but here: if (response.isSuccessful() == false)
It's a quite strange compare a boolean method isSuccessful() with false, the method already return a boolean.

if (response.isSuccessful() == false)

After searching at the movie database api forum , I found this [https://www.themoviedb.org/talk/5667650ec3a36836970002bc][1]
in which it is stated that "The only way we currently support is via query parameters." and there is a big possibility for my problem to be related with the fact that I am using a @Path parameter and not a @Query parameter.
So now the million dollar question is how to convert the

@GET("movie/{id}")
Call<MovieResponse> getMovieDetails(@Path("id") int id, @Query("api_key") String apiKey);


to a Call using the @Query annotation.

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