如何通过Jetpack Compose实现双击点赞动画效果

这篇文章主要介绍如何通过Jetpack Compose实现双击点赞动画效果，文中介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们一定要看完！

实现步骤

先红色画个爱心

Icon(    Icons.Filled.Favorite,    "爱心",    Modifier        .align(Alignment.Center)        tint = Color.Red)

点击事件加动画

双击监听

.pointerInput(Unit) {    detectTapGestures(        onDoubleTap = {          ...        }    )}#### **API 介绍**| API名称 | 作用 || --- | --- || detectTapGestures | 监听点击手势 |> 与 Clickable Modifier 不同的是，detectTapGestures 可以监听更多的点击事件。作为手机监听的基础 API，必然不会存在 Clickable Modifier 所拓展的涟漪效果detectTapGestures 提供了四个可选参数-   onDoubleTap (可选)：双击时回调-   onLongPress (可选)：长按时回调-   onPress (可选)：按下时回调-   onTap (可选)：轻触时回调我们用到的就是`onDoubleTap`

用枚举定义三个变量 开始、显示和消失

enum class LikedStates {    Initial,    Liked,    Disappeared}

remember保持数据状态，mutableStateOf监听状态变化

var transitionState by remember {    mutableStateOf(MutableTransitionState(LikedStates.Disappeared))}

MutableTransitionState包含两个字段：currentState和targetState。currentState初始化为提供的initialState，并且只能通过转换进行变异。targetState也初始化为initialState。可以对其进行变异，以改变使用updateTransition使用MutableTransitionState创建的过渡动画的过程。currentState和targetState都由状态对象支持。

判断拦截数据变化过程，用于实现对应的动画

if (transitionState.currentState == LikedStates.Initial) {    transitionState.targetState = LikedStates.Liked} else if (transitionState.currentState == LikedStates.Liked) {    transitionState.targetState = LikedStates.Disappeared}

开始显示的过度动画

val transition = updateTransition(transitionState = transitionState, label = null)val alpha by transition.animateFloat(    transitionSpec = {       ...    }) {    if (it == LikedStates.Liked) 1f else 0f}

我们要实现有弹性的放大动画，所以利用graphicsLayer实现缩放

graphicsLayer可以应用于

• 缩放（scaleX、scaleY）

• 旋转（rotationX、rotationY、rotationZ）

• 不透明度（alpha）

• 阴影（shadowElevation、shape）

• 剪裁（clip、shape）

定义scale,XY

1 ：1放大所以定义一个就行

val scale by transition.animateFloat(    transitionSpec = {       ....    }) {  ...}

创建浮动动画作为给定变换的一部分targetValueByState用作从目标状态到此动画的目标值的映射

最后在定义三种状态里吗设置对应的参数

 when (it) {        LikedStates.Initial -> 0f        LikedStates.Liked -> 4f        LikedStates.Disappeared -> 2f    }

完整代码

@Suppress("TransitionPropertiesLabel")@Composable fun DoubleTapToLike() {    var transitionState by remember {        mutableStateOf(MutableTransitionState(LikedStates.Disappeared))    }    Box(        Modifier            .fillMaxSize()            .pointerInput(Unit) {                detectTapGestures(                    onDoubleTap = {                        transitionState = MutableTransitionState(LikedStates.Initial)                    }                )            }    ) {        if (transitionState.currentState == LikedStates.Initial) {            transitionState.targetState = LikedStates.Liked        } else if (transitionState.currentState == LikedStates.Liked) {            transitionState.targetState = LikedStates.Disappeared        }        val transition = updateTransition(transitionState = transitionState, label = null)        val alpha by transition.animateFloat(            transitionSpec = {                when {                    LikedStates.Initial isTransitioningTo LikedStates.Liked ->                        keyframes {                            durationMillis = 500                            0f at 0                            0.5f at 100                            1f at 225                        }                    LikedStates.Liked isTransitioningTo LikedStates.Disappeared ->                        tween(durationMillis = 200)                    else -> snap()                }            }        ) {            if (it == LikedStates.Liked) 1f else 0f        }        val scale by transition.animateFloat(            transitionSpec = {                when {                    LikedStates.Initial isTransitioningTo LikedStates.Liked ->                        spring(dampingRatio = Spring.DampingRatioHighBouncy)                    LikedStates.Liked isTransitioningTo LikedStates.Disappeared ->                        tween(200)                    else -> snap()                }            }        ) {            when (it) {                LikedStates.Initial -> 0f                LikedStates.Liked -> 4f                LikedStates.Disappeared -> 2f            }        }        Icon(            Icons.Filled.Favorite,            "点赞",            Modifier                .align(Alignment.Center)                .graphicsLayer(                    alpha = alpha,                    scaleX = scale,                    scaleY = scale                ),            tint = Color.Red        )    }}enum class LikedStates {    Initial,    Liked,    Disappeared}

效果图

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