Is there a better way to write this? ```val someBo...

# compose

[Dominaezzz]

Is there a better way to write this?

val someBoolean = true // this is calculated
val translationSize = 100f // this is calculated

val animatedDelta by animateFloatAsState(if (someBoolean) 0.0f else 1.0f)
val value = if (someBoolean) {
    animatedDelta * -translationSize
} else {
    (1 - animatedDelta) * translationSize
}

[Adam Powell]

Probably with the suspending animate APIs and produceState/LaunchedEffect to avoid recomposing just to finish computing the value

[lhwdev]

Also note that if you read states in lambdas like graphicsLayer { /* here! */ }, it won't trigger recomposition. I would write this:

val animatedDelta by animateFloatAsState(...) // (do not read this in places other than inside graphicsLayer)
Box(Modifier.graphicsLayer { alpha /* or other properties */ = animatedDelta }) {
// maybe put some computations here
}

Maybe using other than graphicsLayer?

[Dominaezzz]

I was using the simple graphicsLayer(translationY = ...) instead of graphicsLayer { ... } . Didn't know the latter was better for recomposition.

[Dominaezzz]

Ha, I was trying to avoid using the suspend APIs to avoid refactoring but it looks like the way to go.

[Dominaezzz]

I'm currently doing something like this.

val value: Float
if (someOtherBoolean) {
   // the code I posted above
} else {
   value = 0.0f
}
Modifier.graphicsLayer(translationY = value)

I had it this way so I could snap stuff back into position.

[Dominaezzz]

I refactored my code to use AnimatableState with the suspend APIs and LaunchedEffect , it works but it's a frame too slow. So I end up seeing jitter in the UI.

[Dominaezzz]

To explain what I'm doing. I have a LazyColumn and I'm animating a swap between two adjacent items. (This is for drag and drop/reordering)
So first I do the swap in the dataset and when the items are composed in their new positions, I translate them to their old positions and then animate them into their new positions.

[lhwdev]

Maybe... did you run that with debug mode?
Or it recomposes every frame it animates?

[Dominaezzz]

I'm on Compose for Desktop and there's no "debug mode" I think. I ran it without the debugger if that's what you're asking.

[Dominaezzz]

With my old code.
• Before swap, everything is fine.
• Swap happens in data set
• When composing, I check for swap then set translation to old position
• Then animate into the new position.
With new AnimatableState
• Before swap, everything is fine.
• Swap happens in data set
• When composing, the item is composed in new position
• Eventually LaunchedEffect catches up and snaps the translation to the old position
• Then animate into the new position

[Dominaezzz]

That's a better explanation of the issue I'm having with AnimatableState .

[Adam Powell]

Can you post your code? Under the hood animateFloatAsState is using the same suspend APIs so there's not something intrinsically different there

[Dominaezzz]

I'm preparing a standalone project to push to GitHub. I'll post a link in a bit when I'm done tidying.

[Dominaezzz]

This is the bit of code https://github.com/Dominaezzz/compose-dnd/blob/master/src/main/kotlin/DragAndDrop.kt?ts=4#L203-L209 . (I might be doing some naughty things with state so brace yourself aha)

[Dominaezzz]

And this is the code migrated over to Animatable https://github.com/Dominaezzz/compose-dnd/compare/animatable?expand=1&ts=4 .

[Dominaezzz]

You'll see in master , the selected item follows smoothly but in the animatable branch, the selected item jitters when it's moved between other items.

[Adam Powell]

avoid CoroutineScope.launch from composable functions, the scope.launch { translation.snapTo(0f) } calls in particular are going to be issues

[Dominaezzz]

Ah I forgot about that. I'm surprised that didn't cause more issues, tbh.

[Dominaezzz]

I've changed them to LaunchedEffect . I think I might need to use the transition API to make this do what I want.

[Adam Powell]

Could be. There are also more animation APIs below Animatable that might be useful in some situations where you're jumping through too many hoops to use Animatable as a source of truth instead of bringing your own