How to make a singleton for retrofit 2?

Question

If there exists multiple retrofit call, how can i make a singleton of a retrofit, so that there won\'t be repeated codes within the class, thereby get rid of unnecessary cod

Answer 1

public class Singleton  {

    private static Singleton INSTANCE = null;

    // other instance variables can be here

    private Singleton() {};

    public static Singleton getInstance() {
        if (INSTANCE == null) {
            INSTANCE = new Singleton();
        }
        return(INSTANCE);
    }

    // other instance methods can follow 
}



import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class RetrofitClient {

    private static Retrofit retrofit = null;

    public static Retrofit getClient(String baseUrl) {
        if (retrofit==null) {
            retrofit = new Retrofit.Builder()
                    .baseUrl(baseUrl)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }
        return retrofit;
    }
}




@Module
public class NetworkModule {

    @Provides
    @Singleton
    public Gson gson() {
        GsonBuilder gsonBuilder = new GsonBuilder();
        return gsonBuilder.create();
    }

    @Provides
    @Singleton
    public HttpLoggingInterceptor loggingInterceptor() {
        HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor(
                message -> Timber.i(message));
        interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
        return interceptor;
    }

    @Provides
    @Singleton
    public Cache cache(File cacheFile) {
        return new Cache(cacheFile, 10 * 1000 * 1000); //10MB Cache
    }

    @Provides
    @Singleton
    public File cacheFile(@ApplicationContext Context context) {
        return new File(context.getCacheDir(), "okhttp_cache");
    }

    @Provides
    @Singleton
    public OkHttpClient okHttpClient(HttpLoggingInterceptor loggingInterceptor, Cache cache) {
        return new OkHttpClient.Builder()
                .addInterceptor(loggingInterceptor)
                .cache(cache)
                .build();
    }

    @Provides
    @Singleton
    public Retrofit retrofit(OkHttpClient okHttpClient, Gson gson) {
        return new Retrofit.Builder()
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create(gson))
                .client(okHttpClient)
                .baseUrl("you/base/url")
                .build();
    }
}