IssueTracker

Jetpack Compose version: 1.7.0-beta04 Jetpack Compose component used: Animation Android Studio Build: N/A Kotlin version: 2.0.0

We are using a custom crossfade implementation to only run animations when a type of the object changes to animate transitions between states in our UI.

@Composable
fun <T : Any> TypeCrossfade(
    state: T,
    modifier: Modifier = Modifier,
    fill: Boolean = true,
    animationSpec: FiniteAnimationSpec<Float> = tween(),
    contentAlignment: Alignment = Alignment.Center,
    content: @Composable context(BoxScope) T.() -> Unit
) {
    val transition = updateTransition(targetState = state, label = "TypeCrossfade")
    transition.Crossfade(
        contentKey = { it::class },
        animationSpec = animationSpec,
        contentAlignment = contentAlignment,
        modifier = modifier.thenIf(fill) { fillMaxSize() },
    ) {
        content(it)
    }
}

However since upgrade to compose 1.7.0 (from 1.6.x) the content of the crossfade no longer recomposes correctly. Despite the incoming state changing, the content recomposes only if the contentKey changes, i.e. the type of the content.

You can reproduce the issue by running the preview provided below

private sealed interface States {
    data class A(val i: Int = 0) : States
    data object B : States
}

@Composable
@Preview(name = "TypeAnimatedContent", showSystemUi = false, showBackground = true, backgroundColor = 0xFFFFFFFF)
private fun TypeAnimatedContentPreview() = OPTheme {
    val states = listOf(
        A(0), A(1), B, A(3)
    )
    var currentState by remember { mutableIntStateOf(0) }

    LaunchedEffect(Unit) {
        while (isActive) {
            delay(1000)
            currentState = (currentState + 1) % states.size
        }
    }
    TypeCrossfade(
        state = states[currentState],
    ) {
        Text(text = toString())
    }
}

The A(0) and A(1) states are never visible. If you replace content key, the transition immediately starts working. If this was changed, then it's a breaking change and a replacement should be provided as we relied on correct recomposition of the content.