Android Jetpack Compose 动画的行为是什么

在我的Android项目中，我正在做一个简单的浮动操作按钮，它可以展开并显示执行不同操作的按钮列表. 为了跟踪FAB的当前状态，我有下一个枚举类

enum class FabState {
    Expanded,
    Collapsed
}

为了显示浮动操作按钮，我有以下可组合函数:

@Composable
fun MultiFloatingActionButton(
    icon: ImageVector,
    iconTint: Color = Color.White,
    miniFabItems: List<MinFabItem>,
    fabState: FabState, //The initial state of the FAB
    onFabStateChanged: (FabState) -> Unit,
    onItemClick: (MinFabItem) -> Unit
) {
    val transition = updateTransition(targetState = fabState, label = "transition")

    val rotate by transition.animateFloat(label = "rotate") {
        when (it) {
            FabState.Collapsed -> 0f
            FabState.Expanded -> 315f
        }
    }

    val fabScale by transition.animateFloat(label = "fabScale") {
        when (it) {
            FabState.Collapsed -> 0f
            FabState.Expanded -> 1f
        }
    }

    val alpha by transition.animateFloat(label = "alpha") {
        when (it) {
            FabState.Collapsed -> 0f
            FabState.Expanded -> 1f
        }
    }

    val shadow by transition.animateDp(label = "shadow", transitionSpec = { tween(50) }) { state ->
        when (state) {
            FabState.Expanded -> 2.dp
            FabState.Collapsed -> 0.dp
        }
    }

    Column(
        horizontalAlignment = Alignment.End
    ) { // This is where I have my question, in the if condition
        if (fabState == FabState.Expanded || transition.currentState == FabState.Expanded) {
            miniFabItems.forEach { minFabItem ->
                MinFab( //Composable for creating sub action buttons
                    fabItem = minFabItem,
                    alpha = alpha,
                    textShadow = shadow,
                    fabScale = fabScale,
                    onMinFabItemClick = {
                        onItemClick(minFabItem)
                    }
                )
                Spacer(modifier = Modifier.size(16.dp))
            }
        }

        FloatingActionButton(
            onClick = {
                onFabStateChanged(
                    when (fabState) {
                        FabState.Expanded -> {
                            FabState.Collapsed
                        }
                        FabState.Collapsed -> {
                            FabState.Expanded
                        }
                    }
                )
            }
        ) {
            Icon(
                imageVector = icon,
                tint = iconTint,
                contentDescription = null,
                modifier = Modifier.rotate(rotate)
            )
        }
    }
}

我定义的常量用于根据FAB状态显示/隐藏按钮的动画.

当我第一次做这个函数时，最初的条件给了我一个不同的行为，并try 了所有可能的条件，我得到了3个不同的结果:

• 第一个条件: if (transition.currentState == FabState.Expanded) {...}个

结果:animation not loading from collapsed to expanded, but it does from expanded to collapsed人

• 第二种情况:if (fabState == FabState.Expanded) {...}

结果:animation loading from collapsed to expanded, but not from expanded to collapsed人

第三个条件(我现在正在使用的条件): if (fabState == FabState.Expanded || transition.currentState == FabState.Expanded) {...}个

结果:animation loading in both ways人

所以我的问题是:每一种情况是如何改变动画的行为的？

任何帮助都将不胜感激.提前谢谢你