A bit of an architecture question I suppose. I have this bottom sheet that's a picker and it can essentially be called from any screen.

bottomSheet(route = Screen.NumberPickerBottomSheet.route) {
  NumberPickerBottomSheet()
}

In the bottom sheet when the "Save" button is hit, I want to update the number value to the screen/VM that started the bottomSheet. Since it was a navigation event that started the bottom sheet, I can't pass a lambda of like

onNumUpdateEvent

. What's the best way to go about this? The only other thing that comes to mind is for the screen/VM to implement some interface or something? Or maybe I just save the state in some Activity level VM? Edit: Or another option is to use the navController in the bottomsheet and use that to get the previous entry and get the VM/cast to the VM and update it that way?

using compose navigation, you can use the savedStateHandle of the previousBackStackEntry to communicate to the screen that launches this picker destination

NumberPickerBottomSheet(
    onPickNumber = { value ->
        navController.previousBackStackEntry?.savedStateHandle?.set(key, value)
    }
)

Oh hm. Interesting. Do those values only get "transfered" once the bottom sheet collapses/goes away though? example: In the activity/fragment world with extras you only got the "extra" once the activity/fragment was closed.

One step backwards, but does this need to be in the navigation graph? Let's say this wasn't a bottom sheet and it was just used everywhere, it could be a normal composable with a lambda call back (i.e nothing to do with navigation). I haven't used bottom sheets in compose yet since I keep hearing they're nightmares so plz excuse this if the suggestion doesn't make sense

It could arguably just be in every destination yes. But I have a lot of screens (40) and so adding this to every screen seems subpar, although it would 100% be easier on the state management side of things.

Oh hm. Interesting. Do those values only get "transfered" once the bottom sheet collapses/goes away though? example: In the activity/fragment world with extras you only got the "extra" once the activity/fragment was closed.

You can see the values immediately, because the previous destination is still active.

Thanks. appreciate the tips. TIL

I did something like this: https://gist.github.com/micHar/716d810f319973beb86ebbb1a5257be8 Although I'm exploring using a navgraph scoped viewmodel for communication between screens in a single navgraph and wondering what the most elegant approach is.