presenter.java

public class ContributorsPresenter extends MvpBasePresenter<ContributorsView> {
    private AppRepository appRepository;
    private Subscription subscription;

    public ContributorsPresenter(final AppRepository appRepository) {
        this.appRepository = appRepository;
    }

    public void loadContributors(String owner, String repo, boolean pullToRefresh) {
        if (isViewAttached()) {
            getView().showProgress(pullToRefresh);
        }

        subscription =
            appRepository.contributors(owner, repo).subscribe(new Subscriber<List<Contributor>>() {
                @Override
                public void onCompleted() {
                    Timber.d("Finished loading contributors.");
                }

                @Override
                public void onError(final Throwable e) {
                    if (isViewAttached()) {
                        getView().showError(e.toString());
                    }
                }

                @Override
                public void onNext(final List<Contributor> contributors) {
                    if (!isViewAttached()) {
                        return;
                    }

                    if (contributors != null && !contributors.isEmpty()) {
                        getView().showContributors(contributors);
                    } else {
                        getView().showEmpty();
                    }
                }
            });
    }
      ...
}