Create an Observer over a dynamic ArrayList

[Juan Pablo Vergara Villarraga]

I need to create an Observer over an array which is constantly changing (adding elements).

I am using Obserable.from(Iterable) but it seems that it creates the Observable over the ArrayList as it is at the moment of the creation.

I need the Observer to be notified and the Action to be executed everytime the ArrayList gets a new element added.

[Dávid Karnok]

There are many ways of implementing this, depending on how much control do you have over the party that is adding to list. For example:

public class ObservableListExample {

    public static class ObservableList<T> {

        protected final List<T> list;

        protected final PublishSubject<T> onAdd;

        public ObservableList() {

            this.list = new ArrayList<>();

            this.onAdd = PublishSubject.create();

        }

        public void add(T value) {

            list.add(value);

            onAdd.onNext(value);

        }

        public Observable<T> addObservable() {

            return onAdd;

        }

    }

    

    public static void main(String[] args) {

        ObservableList<Integer> olist = new ObservableList<>();

        

        olist.addObservable().subscribe(System.out::println);

        

        olist.add(1);

        olist.add(2);

        olist.add(3);

[Juan Pablo Vergara Villarraga]

Thank you so much Dávid. Since I´m new to RxJava I didn´t know the Subject classes. I was trying to do so using the basic creation methods for Observables.

Your example works pretty well.

Thanks again.