Rxjava多个可观察列表

Question

I have two observable list of String. I want to achieve something like this in rxjava using zip or any other operation.

If list1 has data and list2 doesn't have any data - consider the dataset of list1

If list1 has no data and list2 has any data - consider the dataset of list2

If list1 and list2 both have data, then take the intersection of both list

List1 has 0-n elements and list2 has 0-m elements.

Answer 1

There's no official way to do this with RxJava. I would suggest using flatMap on one of the Observables and then filtering each element through the other Observable. I can't test this right now, but it should work.

Edit: Something like:

list1
  .defaultIfEmpty(/*Observable with empty string, for instance (for the empty case)*/)
  .flatMap { element ->
    return list2.defaultIfEmpty(element).filter(x -> x == element);
  }
  .observeOn(...)
  .subscribeOn(...)
  .subscribe(...)

It has been months since I used RxJava, but something of this sort should work.

Answer 2

You can use zip to have both lists ready, then you need to chose based on their state:

Single<List<Integer>> singleList1 = ...
Single<List<Integer>> singleList2 = ...

Single.zip(singleList1, singleList2, (list1, list2) -> {

    if (list1.isEmpty()) {
        return list2;
    }
    if (list2.isEmpty()) {
        return list1;
    }

    Set<Integer> set = new HashSet<>(list1);
    List<Integer> result = new ArrayList<>(list2.size());

    for (Integer i : list2) {
        if (set.contains(i)) {
            result.add(i);
        }
    }

    return result;
});