Hello guys. Have small issue. I have nav host with...

# compose

[Jasmin Fajkic]

Hello guys. Have small issue. I have nav host with composable and bottomSheet ( from accompanist ). In my composable route i set custom BackHandler. But when i navigate from that screen to bottom sheet screen , my bottom sheet screen inherit back handler behaviour from previous screen. Any chance to solve it 😞 ?

[Ian Lake]

Well your composable destination is still visible underneath the bottom sheet right? Which would mean that the BackHandler is still part of composition and still receiving back events unless you make it not enabled (i.e., pass some state that is false when you construct the BackHandler)

[Jasmin Fajkic]

Yeah i made it like that and in my bottomSheet i do this

val observer = remember {
    LifecycleEventObserver { _, event ->
        if (event.name == Lifecycle.Event.ON_STOP.name) {
            onSheetClose()
        }
    }
}
val lifecycle = LocalLifecycleOwner.current.lifecycle
DisposableEffect(lifecycle, observer) {
    lifecycle.addObserver(observer)
    onDispose { lifecycle.removeObserver(observer) }
}

[Ian Lake]

When a floating window destination (like your bottom sheet) is on top of your composable destination, the Lifecycle of your composable destination will be STARTED, instead of RESUMED. You could use that as a signal for if your BackHandler should be enabled or not

[Ian Lake]

Yeah, keep in mind in the future world of Predictive Back, you'll want to disable the BackHandler if it isn't supposed to intercept back - that way the default NavController one will pick it up (which is important since that is going to matter for running animations)

[Ian Lake]

So really you'd want to use that same kind of DisposableEffect approach to make the current Lifecycle.State exposed as compose state, then use that as input into your BackHandler, e.g.

val lifecycle = LocalLifecycleOwner.current.lifecycle
val currentLifecycleState = remember(lifecycle) { mutableStateOf(lifecycle.currentState) }
// Do a DisposableEffect to update currentLifecycleState
BackHandler(currentLifecycleState.isStateAtLeast(Lifecycle.State.RESUMED) {
  // Your back logic
}

[Jasmin Fajkic]

aha thx a lot Ian for clarification you are best as always! ❤️

[Ian Lake]

Hopefully that whole DisposableEffect + LifecycleObserver will go away when this feature request is finished up here soon: https://issuetracker.google.com/235529345

[Ian Lake]

Which will give you a nice way of getting Compose State out of a Lifecycle