Is there a way to tell is a composable running in an initial composition or a recomposition? I’m bui...

# compose

[Vsevolod Ganin]

Is there a way to tell is a composable running in an initial composition or a recomposition? I’m building yet another screen transition composable based on Crossfade and I want it not animate anything on initial composition

[Vsevolod Ganin]

I can only think about a hack with remember

@Composable
private fun isInitialComposition(): Boolean {
    var isInitialComposition by remember { mutableStateOf(true) }
    return isInitialComposition.also { isInitialComposition = false }
}

But maybe there is a conventional way to do this?

[Sean McQuillan [G]]

@Doris Liu for animations @Leland Richardson [G] for clever composition tricks 🙂

[Zach Klippenstein (he/him) [MOD]]

I think you can do something like currentComposer.isInserting - true means it’s the first composition.

But for this case, that feels like a hack. A lot of the animation tools already won’t animate when their target is the same as their starting value.

[Adam Powell]

not sure I'd count on that composer API sticking around as public

[Doris Liu]

You could initialize a value with something that is not meaningful. For example, if you build animations based on CrossFade, you could initialize its internal state to null (

var state : CrossfadeState<T>? by remember { mutableStateOf(null) }

), and update it after your first-run logic.

[Leland Richardson [G]]

currentComposer.inserting is the most correct and efficient way to do this but I'd be curious to see exactly how you're using it

[Vsevolod Ganin]

Thanks for all responses! I’ll try currentComposer.inserting in a moment and share my code with you guys

[Vsevolod Ganin]

Sorry for delay, here is what I came up with: https://gist.github.com/vganin/4e846beb8913c70b4886693102ac4b47
(props to mr. @cb, I based my solution on his old gist)

[Zach Klippenstein (he/him) [MOD]]

I’m no expert on the transition animation apis, but my instinct is that if you have to use inserting with it, there’s probably a better way to write your animation logic, or the apis are missing a feature.

[Adam Powell]

yeah the inserting is likely to be acting as a proxy for some other animation state that you probably want to hoist explicitly and construct into a particular initial state to determine this behavior

[Adam Powell]

inserting seems like the most correct and efficient way to answer what is likely to be the wrong question 🙂

[Doris Liu]

I would suggest setting the initState (for initializing TransitionAnimation ) using the same logic as how you determine target state here. That way when you call toState() in the first composition, you'll get an no-op, as the target state is the same as the initial state.

[Doris Liu]

Cool implementation BTW. 👍

[Vsevolod Ganin]

Thanks for your ideas with initial state, really appreciated! I managed to get away from using inserting by setting appropriate initial state in remember closure. If you are interested, here is what changed: https://gist.github.com/vganin/4e846beb8913c70b4886693102ac4b47/revisions#diff-79f7b006e814e81e4584b239fd3c45426def70b13bf091e5a6b1c0911bedd108