MVPContract

// его можно положить в ../presentation/contract

public interface PhotosContract {

    interface Model {
        // Presenter -> Model
        void loadPhotos(Integer page);
    }

    interface View {
        // Presenter -> View
        void displayPhotos(List<Photo> photos);
        void displayError();
    }

    interface Presenter {
        // View -> Presenter
        void onViewCreated();
        void loadNextPhotos();
        void onViewDestroyed();

        // Model -> Presenter
        void onPhotosLoaded(List<Photo> photos);
        void onLoadFailure();
    }

}


...

class UnsplashService implements PhotosContract.Model {

    private PhotosContract.Presenter presenter;

    ...

}

class WPFragment extends Fragment implements PhotosContract.View {

    private PhotosContract.Presenter presenter;

    ..

}

class PhotosPresenter implements PhotosContract.Presenter {

    private PhotosConract.Model model;
    private PhotosContract.View view;

    ...

}