How to represent Observable.empty() with LiveData in Android?

Question

Rx has Observable.empty() that represents nothing will be notified.

Is there an equivalent class (or something) in Android Architecture Components LiveData?

Answer 1

You will always get the currently set value on observing.

Therefore, your best bet is either to handle null values, or use LiveData<Optional<T>> (or, in Kotlin, LiveData<T?>).

Answer 2

If you are saying that you want to expose a LiveData that indicates to the caller that it will never emit a value, I don't think you have a way to express that with architecture components, since LiveData can always emit values of its generic type.

You could use LiveData<Void> in Java or LiveData<Unit> in Kotlin to say that the emitted values have no type, but I believe they can still be observed, and its observers can still be triggered with values that contain no data. LiveData doesn't have a concept of saying "I'm done and I will never emit anything ever again". A Kotlin Flow might be better for that case, since a Flow can complete with no more emissions.