Dagger2 learning is still difficult and am trying to learn. Have setup a project using new dagger android to avoid injecting inside activity class. So far it's working but need to use retrofit injected in presenter class. Added retrofit module in AppComponent but apiService class method getting null when call from presenter class. Need to know how to inject properly.

AppComponent.java

@Singleton

@Component(modules = {

    /* Use AndroidInjectionModule.class if you're not using support library */

    AndroidSupportInjectionModule.class,

    AppModule.class,

    BuildersModule.class,

    RetrofitModule.class})

public interface AppComponent {



@Component.Builder

interface Builder {

    @BindsInstance

    Builder application(BaseApplication application);



    Builder retrofitModule(RetrofitModule retrofitModule);



    AppComponent build();

}



  void inject(BaseApplication app);

}

AppModule.java

@Module

class AppModule {



    @Provides

    Context provideContext(BaseApplication application) {

        return application.getApplicationContext();

    }

}

BuildersModule.java

@Module

public abstract class BuildersModule {



    @ContributesAndroidInjector(modules = {SplashViewModule.class, SplashModule.class})

    abstract SplashActivity bindSplashActivity();



    // Add bindings for other sub-components here

}

BaseApplication.java

public class BaseApplication extends Application implements HasActivityInjector {



    @Inject

    DispatchingAndroidInjector<Activity> dispatchingAndroidInjector;



    @Override

    public void onCreate() {

        super.onCreate();



        //configure timber for logging

        if (BuildConfig.DEBUG) {

            Timber.plant(new Timber.DebugTree());

        }



        DaggerAppComponent

                .builder()

                .application(this)

                .retrofitModule(new RetrofitModule())

                .build()

                .inject(this);

    }





    @Override

    public AndroidInjector<Activity> activityInjector() {

        return dispatchingAndroidInjector;

    }

}

RetrofitModule.java

@Module

public class RetrofitModule {



    //get retrofit instance

    @Singleton

    @Provides

    public UserAuthService getRestService() {



        Gson gson = new GsonBuilder()

                .setLenient()

                .create();



        Retrofit retrofit = new Retrofit.Builder()

                .baseUrl(ApiConstants.BASE_URL)

                .addConverterFactory(GsonConverterFactory.create(gson))

                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())

                .client(getOkHttpClient())

                .build();



        return retrofit.create(UserAuthService.class);

    }

}

UserAuthService.java

public interface UserAuthService {



    @GET("v2/5be345062f00006b00ca22c4")

    Observable<Example> getExampleResponse();

}

SplashModule.java

@Module

public class SplashModule {



    @Provides

    SplashPresenter provideSplashPresenter(SplashView splashView) {

        return new SplashPresenter(splashView);

    }

}

SplashViewModule.java

@Module

public abstract class SplashViewModule {



    @Binds

    abstract SplashView provideSplashView(SplashActivity splashActivity);



}

SplashPresenter.java

class SplashPresenter extends BasePresenter<SplashView> {





    @Inject

    @Named(ValueConstants.MAIN_THREAD)

    Scheduler mMainThread;



    @Inject

    @Named(ValueConstants.NEW_THREAD)

    Scheduler mNewThread;



    @Inject

    UserAuthService userAuthService;



    SplashPresenter(SplashView view) {

        super(view);

    }



    //test purpose

    public void sayHello() {



        userAuthService.getExampleResponse()

                .observeOn(mMainThread)

                .subscribeOn(mNewThread)

                .subscribe(new Observer<Example>() {

                    @Override

                    public void onSubscribe(Disposable d) {



                    }



                    @Override

                    public void onNext(Example example) {

                        Timber.d("example %s", example.toString());

                    }



                    @Override

                    public void onError(Throwable e) {

                        e.printStackTrace();

                    }



                    @Override

                    public void onComplete() {



                    }

                });

    }

}

here "userAuthService.getExampleResponse()" getting null. I think presenter need to know about RetrofitModule injection. So I need to fix this and how?

I would add those dependencies to the constructor of SplashPresenter and add the @Inject annotation to it. Dagger2 supports constructor injection and all the dependencies you need are resolvable (and you can also get rid of SplashModule)

class SplashPresenter extends BasePresenter<SplashView> {



   private Scheduler mMainThread;



   private Scheduler mNewThread;



   private UserAuthService userAuthService;



  @Inject

  SplashPresenter(SplashView view, UserAuthService userAuthService, @Named(ValueConstants.NEW_THREAD) Scheduler newThread,  @Named(ValueConstants.MAIN_THREAD) Scheduler mainThread) {

        super(view);

        this.userAuthService = userAuthService;

        mNewThread = newThread;

        mMainThread = mainThread;

  }