onCompletion not called while using Koltin Flow with LiveData

Question

So here is what I was trying to do with Flow , I am showing a ProgressBar in onStart and trying to hide the ProgressBar in onCompletion .

In ViewModel class appDatabase.eventDao().getAllEvents() returns Flow<List<EntityEvents>

@ExperimentalCoroutinesApi
val allEvents: LiveData<Outcome<List<Event>>> = _fetchEvents.switchMap { _ ->
    appDatabase.eventDao().getAllEvents()
        .map { eventListMapper.map(it) }
        .map { sortEventsBasedOnPreference(it) }
        .flowOn(Dispatchers.IO)
        .map { Outcome.success(it) }
        .onStart { emitLoading(true) }
        .onCompletion { emitLoading(false) }
        .catch { emitFailure(it, R.string.err_something_wrong) }
        .asLiveData(context = viewModelScope.coroutineContext)
}

All working fine, what I am not able to figure out why is onCompletion not called when the task is completed?

Answer 1

if appDatabase.eventDao().getAllEvents() is based Room on Flow, never called onCompletion() .

Why?

Because getAllXXX() Query is 'Hot'. Actually, query is not completed. Only data is emited.

When the data changes, the query will emit data again.