共享元素是通过在Compose中使用Transition API实现的。该API在为不同元素提供进出动画时非常有用。在联合使用Transition和NavigationView时,可以使用rememberNavController()
函数来创建导航控制器,然后定义转换。在转换中,将SharedAxis对象分配给目标和源。下面是一个示例代码:
val navController = rememberNavController()
val transition = updateTransition(navController, label = "nav")
val toDown = SharedAxis(
motionSpec = TweenSpec(durationMillis = 300)
)
val toUp = SharedAxis(
motionSpec = TweenSpec(durationMillis = 300),
direction = SharedAxis.Y
)
val backstackEntry = navController.currentBackStackEntryAsState()
val destination = backstackEntry.value?.destination?.route
// 定义转换和源
val triggerBackwardAnimation = destination?.let {
transition.animate(direction = "forward$it") {
if (it == "secondScreen") toDown else toUp
}
}
// 定义目标
val triggerForwardAnimation = destination?.let {
transition.animate(direction = "backward$it") {
if (it == "secondScreen") toUp else toDown
}
}
// 使用共享元素
NavHost(navController = navController, startDestination = "firstScreen") {
composable("firstScreen") {
FirstScreen(
onClick = { route -> navController.navigate(route) },
triggerBackwardAnimation = triggerBackwardAnimation
)
}
composable("secondScreen") {
SecondScreen(triggerForwardAnimation = triggerForwardAnimation)
}
}
此示例中,我们为向前和向后导航定义了两种共享元素。界面之间的动画可以根据界面之间的关系切换。这是仅处理带有Jetpack Compose的动画的一种方法。