IssueTracker

Jetpack Compose version: BOM 2025.01.01 = animation-core 1.7.7
Jetpack Compose component used: createChildTransition
Android Studio Build: Ladybug Feature Drop | 2024.2.2
Kotlin version: 2.1.10

Example using MutableTransitionState:

val state = remember { MutableTransitionState(0) }
val transition = rememberTransition(state)
val child = transition.createChildTransition { it > 1 }

// Animate something with a noticeable transition spec.
val color by child.animateColor(transitionSpec = { tween(durationMillis = 2000) }) {
    if (it) Color.Red else Color.Blue
}

Row {
    OutlinedButton(onClick = {
        state.targetState = state.currentState - 1
    }) {
        Text("-")
    }

    Text("${state.currentState}", color = color)

    OutlinedButton(onClick = {
        state.targetState = state.currentState + 1
    }) {
        Text("+")
    }
}

1. The first time the "+" button is clicked, the text transitions to "1" immediately.
2. The second time the "+" button is clicked, the color and text take less than 2 seconds to transition and appear to happen almost immediately.
3. If the "-" button is clicked, it takes 2 seconds to transition the color and text.
   1. From here, clicking "-", then "+", then "+" again; will cause the same behavior in (2) again.
   2. However, repeatedly clicking "+" and "-" to change the color and text will result in the 2-second transition.

Experimenting with this, it seems if the state object alternates between states 1 and 2, the correct transition is used. But if the state object ever ends up at any other value, the next time a color transition is made, it happens almost immediately.

Experimenting with SeekableTransitionState results in something similar, but only the first time the transition happens.

Running the debugger, it seemed the reason the transition was happening quickly is coming from the TransitionAnimationState#updateTargetValue function. In the cases when the transition happens quickly, it looks like the isInterrupted argument to updateAnimation is true, and is causing it to use the interruptionSpec instead. SeekableTransitionState somehow bypasses this on following calls because isSeeking is true. But I could be totally wrong and gotten turned around in the code.