EventViewModel.kt

@HiltViewModel
class EventViewModel @Inject constructor(
    private val savedStateHandle: SavedStateHandle,
    // ...
) : ViewModel() {

    private val _selectedEventId = savedStateHandle.getStateFlow<Int?>(
        KEY_SELECTED_EVENT_ID, null
    )
    private val _eventFilter = savedStateHandle.getStateFlow<EventFilter>(
        KEY_EVENT_FILTER, EventFilter.ALL
    )
    
    // ...

    fun setSelectedEventId(id: Int?) {
        savedStateHandle[KEY_SELECTED_EVENT_ID] = id
    }

    fun setEventFilter(filter: EventFilter) {
        savedStateHandle[KEY_EVENT_FILTER] = filter
    }

    companion object {
        private const val KEY_SELECTED_EVENT_ID = "selected_event_id"
        private const val KEY_EVENT_FILTER = "event_filter"
    }
}