SwiftUI withAnimation完成回调 [英] SwiftUI withAnimation completion callback

问题描述

我有一个基于某些状态的swiftUI动画:

I have a swiftUI animation based on some state:

withAnimation(.linear(duration: 0.1)) {
    self.someState = newState
}

以上动画完成时是否触发了回调?

Is there any callback which is triggered when the above animation completes?

如果没有关于如何在SwiftUI中使用完成块来完成动画的建议，但不是withAnimation，我也欢迎那些人.

If there are any suggestions on how to accomplish an animation with a completion block in SwiftUI which are not withAnimation, I'm open to those as well.

我想知道动画何时完成，因此我可以做其他事情，就本例而言，我只想在动画完成时打印到控制台.

I would like to know when the animation completes so I can do something else, for the purpose of this example, I just want to print to console when the animation completes.

推荐答案

Guy Javier在此博客上描述了如何使用GeometryEffect来获得动画反馈，在他的示例中，他检测到动画何时达到50％，因此他可以翻转视图并使它看起来像具有两个侧面

On this blog this Guy Javier describes how to use GeometryEffect in order to have animation feedback, in his example he detects when the animation is at 50% so he can flip the view and make it looks like the view has 2 sides

这是全文的链接，其中包含很多解释: https://swiftui -lab.com/swiftui-animations-part2/

here is the link to the full article with a lot of explanations: https://swiftui-lab.com/swiftui-animations-part2/

我将在此处复制相关代码段，以便即使该链接不再有效，答案也仍然是相关的:

I will copy the relevant snippets here so the answer can still be relevant even if the link is not valid no more:

在此示例中，当角度在90到270之间然后为假时，@Binding var flipped: Bool变为true.

In this example @Binding var flipped: Bool becomes true when the angle is between 90 and 270 and then false.

struct FlipEffect: GeometryEffect {

    var animatableData: Double {
        get { angle }
        set { angle = newValue }
    }

    @Binding var flipped: Bool
    var angle: Double
    let axis: (x: CGFloat, y: CGFloat)

    func effectValue(size: CGSize) -> ProjectionTransform {

        // We schedule the change to be done after the view has finished drawing,
        // otherwise, we would receive a runtime error, indicating we are changing
        // the state while the view is being drawn.
        DispatchQueue.main.async {
            self.flipped = self.angle >= 90 && self.angle < 270
        }

        let a = CGFloat(Angle(degrees: angle).radians)

        var transform3d = CATransform3DIdentity;
        transform3d.m34 = -1/max(size.width, size.height)

        transform3d = CATransform3DRotate(transform3d, a, axis.x, axis.y, 0)
        transform3d = CATransform3DTranslate(transform3d, -size.width/2.0, -size.height/2.0, 0)

        let affineTransform = ProjectionTransform(CGAffineTransform(translationX: size.width/2.0, y: size.height / 2.0))

        return ProjectionTransform(transform3d).concatenating(affineTransform)
    }
}

您应该能够将动画更改为所需的动画，然后获得绑定以更改父级的状态.

You should be able to change the animation to whatever you want to achieve and then get the binding to change the state of the parent once it is done.

这篇关于SwiftUI withAnimation完成回调的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！