Unexpected Behavior When Using Flow with StateFlow in a ViewModel in Kotlin
I'm writing unit tests and After trying multiple solutions online, I still can't figure this out. I've been banging my head against this for hours. I'm sure I'm missing something obvious here, but I'm experiencing unexpected behavior when trying to combine a `Flow` with `StateFlow` in my ViewModel. I have a `StateFlow` that holds the current state of a list of items, and I'm trying to update this state based on a source `Flow` that emits new items. However, while the `StateFlow` is correctly updated, I occasionally notice that my UI does not reflect these changes as expected, especially after rapid emissions from the source `Flow`. Here’s a simplified version of what I have: ```kotlin class MyViewModel : ViewModel() { private val _items = MutableStateFlow<List<Item>>(emptyList()) val items: StateFlow<List<Item>> = _items.asStateFlow() fun fetchItems() { viewModelScope.launch { getItemsFlow().collect { newItems -> _items.value = newItems // Updating StateFlow } } } } ``` And this is how I’m collecting the `items` in my Fragment: ```kotlin class MyFragment : Fragment() { private lateinit var viewModel: MyViewModel override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) viewModel = ViewModelProvider(this).get(MyViewModel::class.java) lifecycleScope.launchWhenStarted { viewModel.items.collect { items -> // Update UI with the new list updateUI(items) } } } } ``` The `getItemsFlow()` function is defined like this: ```kotlin fun getItemsFlow(): Flow<List<Item>> = flow { // Simulate fetching data from a remote source emit(listOf(Item(1), Item(2))) delay(1000) emit(listOf(Item(3), Item(4))) // This reflects in UI but sometimes it doesn't! } ``` The issue arises when multiple items are emitted quickly, and the UI seems to lag behind the latest state from `_items`. The UI sometimes shows an older list instead of the most recent one. I’ve checked for any heavy computation or blocking calls in the `updateUI()` method, but everything seems to be off the main thread. Does anyone have insights on why the UI might not be reflecting the latest updates from `StateFlow`? Is there something I might be missing in terms of ordering or handling rapid emissions? Any ideas what could be causing this? My development environment is Linux. My development environment is Windows. I'm coming from a different tech stack and learning Kotlin.