I m wondering if I m doing something wrong when collecting `

Question

I m wondering if I m doing something wrong when collecting `StateFlow` from Compose the issue is that the state always restarts from initial state when switching between screens on bottom nav This is an issue when the VM has something different than the initial state as for some reason the Compose local state always restarts from intial state before getting the updated state from the VM On the VM side my flow looks as follows ``` public val viewState StateFlow lt ScreenState gt = internalState stateIn clientScope SharingStarted WhileSubscribed ScreenState showLoading = true ``` And on my Compose screen collection looks like so ```fun Screen viewModel ViewModel = getViewModel val lifecycleOwner = LocalLifecycleOwner current val viewStateFlow = remember viewModel viewState lifecycleOwner viewModel viewState flowWithLifecycle lifecycleOwner lifecycle Lifecycle State STARTED val viewState by viewStateFlow collectAsState ViewModel ScreenState showLoading = true Logger i VM state $ viewModel viewState value 1 Logger i Screen local state is $ viewState 2```

Matti MK · Answer

A bit better explanation the VM makes a network call upon init that eventually switches the ScreenState to `showLoading = false` Once the screen is entered the first time the initial state is correct but if I navigate to another screen and then back to this screen the VM state will no longer be `showLoading = true` however the `viewState` local to Compose Screen always restarts from the `showLoading = true` before getting the updated value from the VM So in the above sample prints of ` 1` and ` 2` will print out different values when entering the screen after `viewModel viewState value ` = initial value

Matti MK · Answer

Just to add I m somewhat confident the issue is not in the bottom navigation I have a screen that doesn t collect external state when navigating between screens it does keep it s internal state just fine scroll positions etc

Matti MK · Answer

Should I ignore the `StateFlowValueCalledInComposition` and set the initial value as what ever is on the VM s state everything works just fine `val viewState by viewStateFlow collectAsState viewModel viewState value ` I guess this is not the way to go sweat smile

Albert Chang · Answer

You are not collecting a `StateFlow` `viewStateFlow` is a `Flow` so you must specify an initial value yourself `val viewState by viewStateFlow collectAsState viewModel viewState value ` actually makes sense if you really want to use `flowWithLifecycle`

Matti MK · Answer

Ah right thanks Somehow I missed that I m still pretty fresh with this so considering I am exposing a StateFlow that I would like to collect safely i e respecting lifecycles would it then make sense to use the viewState value or go another route I had a bit of a hard time finding any samples or decent docs that d shed light on this

Albert Chang · Answer

It makes sense

Stylianos Gakis · Answer

Why are you doing all this ceremony inside the composable when it could all just be `val viewState by viewModel viewState collectAsState ` Your VM viewState has a loading = true as a default anyway inside the `stateIn` and it by itself can launch the coroutine and change the internalState which will automatically change the `viewState` I must be misunderstanding something here

Matti MK · Answer

Thanks thumbsup To be honest I don t quite remember where this came from but I seem to remember here <https medium com androiddevelopers a safer way to collect flows from android uis 23080b1f8bda> That is converting the `StateFlow` to `Flow` in order to have lifecycle based consuming of the flow With that in mind I don t think the `val viewState by viewModel viewState collectAsState ` respects the consumer s lifecycle however using `SharingStarted WhileSubscribed` might have the same effect

Stylianos Gakis · Answer

As I understand it yes it should respect it due to the WhileSubscribed it uses a `produceState` which it is launched when entering composition and stops when exiting composition this is what you want to achieve is it not

Matti MK · Answer

Yes it is exactly what I want thumbsup thank you I ll give it a go

Stylianos Gakis · Answer

And you may want to look into <https medium com androiddevelopers things to know about flows sharein and statein operators 20e6ccb2bc74|this article> and where it mentions Tip for Android apps about why you may want to add a parameter to your `WhileSubscribed`

Matti MK · Answer

Much appreciated thank you thumbsup