MVVM with RxJava without DataBinding

Question

After reading a lot of articles about MVVM and RxJava, I need to implement the simplest demo to catch the idea well without using DataBinding

But I got stuck in the way how the ViewModel will notify the View (Activity) with the list of data

My ViewModel contain fetchGitHub() which using RxJava in this way

io.reactivex.Observable<List<Repo>> reposReturnedObservable = githubClient.reposForUser(user);

    reposReturnedObservable
            .subscribeOn(Schedulers.newThread())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new Observer<List<Repo>>() {
                @Override
                public void onError(Throwable e) {

                }

                @Override
                public void onComplete() {

                }

                @Override
                public void onSubscribe(Disposable d) {
                    compositeDisposable.add(d);
                }

                @Override
                public void onNext(List<Repo> repos) {
                    data = repos;
                }
            });

What is the missing lines here to update the view with the data

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    viewModel = new ViewModel();
    viewModel.fetchGitHub("square");

}

Answer 1

fetchGitHub() should return an Observable, so that the Activity can subscribe to it.

ViewModel:

public class ViewModel {

    public Observable<List<Repo>> fetchGitHub(String userName) {
        return githubClient.reposForUser(user);
    }

}

Activity:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    TextView listSizeTextView = findViewById(R.id.listSizeTextView);

    viewModel = new ViewModel();
    viewModel.fetchGitHub("square")
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(list -> listSizeTextView.setText("list size: " + list.size()));
}

Above example does not store the subscription to provide you with a simplified answer but in real practice, make sure to clear subscriptions like you did in your example.