RxSearch.java

public class RxSearch {

    public static Observable<String> fromSearchView(@NonNull final SearchView searchView) {
        final BehaviorSubject<String> subject = BehaviorSubject.create("");

        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {

            @Override
            public boolean onQueryTextSubmit(String query) {
                subject.onCompleted();
                return true;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                if (!newText.isEmpty()) {
                    subject.onNext(newText);
                }
                return true;
            }
        });

        return subject;
    }
}