RxJava count() when one of two observable is not compled - rx-java2

Question

I want to count items from stream Observable when trigger is not completed. I want to update View by size of stream when trigger occurs. As long as trigger not completed Consumer not invoking accept(). How I can resolve it?
Observable<Long> trigger = Observable.interval(2000L, TimeUnit.MILLISECONDS);
Observable<Long> stream = trigger
.flatMap(new Function<Long, ObservableSource<?>>() {
#Override
public ObservableSource<?> apply(Long aLong) throws Exception {
return Observable.just("A", "B", "C"); //completed observable
}
})
.count()
.toObservable();
stream.subscribe(new Consumer<Long>() {
#Override
public void accept(Long size) throws Exception {
Log.e("Elements: ", size.toString());
}
});

Answer 1

Do a rolling count with scan:
Observable<Long> trigger = Observable.interval(2000L, TimeUnit.MILLISECONDS);
Observable<Long> stream = trigger
.flatMap(new Function<Long, ObservableSource<String>>() {
#Override
public ObservableSource<String> apply(Long aLong) throws Exception {
return Observable.just("A", "B", "C"); //completed observable
}
})
.scan(0L, new BiFunction<Long, String, Long>() {
#Override public Long apply(Long a, String b) {
return a + 1;
}
})
;
stream.subscribe(new Consumer<Long>() {
#Override
public void accept(Long size) throws Exception {
Log.e("Elements: ", size.toString());
}
});