如何对两个动画之间有延迟进行排序

Question

我有一个UIImageView，我想旋转 180 度，占用 1 秒，然后我想在这个位置等待 1 秒，然后旋转 180 度回到原来的位置，占用 1 秒。

我如何做到这一点？我已经尝试了 100 种方法，但它一直在回弹而不是回旋

编辑：我忘了补充我需要这个无限期地重复

Answer 1

您需要做的就是创建一个keyFrame animations。它旨在将多个动画链接在一起，并在第一个关键帧中将您的 UIImageView 子类旋转 PI，然后在第二个关键帧中将其转换回 identity。

        let rotateForwardAnimationDuration: TimeInterval = 1
        let rotateBackAnimationDuration: TimeInterval = 1
        let animationDuration: TimeInterval = rotateForwardAnimationDuration + rotateBackAnimationDuration

        UIView.animateKeyframes(withDuration: animationDuration, delay: 0, options: [], animations: { 
            UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: rotateForwardAnimationDuration) {
                self.imageView.transform = CGAffineTransform(rotationAngle: .pi)
            }

            UIView.addKeyframe(withRelativeStartTime: 0.5, relativeDuration: rotateBackAnimationDuration) { 
                self.imageView.transform = .identity 
            }
        })

结果：

编辑： 这是一个如何使其无限期运行的示例。我想您的图像在 viewController 中，并且您持有对 imageView 的一些引用。

例如，在viewDidAppear，调用触发动画的函数，然后在动画的完成块中，再次调用相同的函数。

class ViewController: UIViewController {

    @IBOutlet weak var imageView: UIImageView!

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        self.runRotateAnimation()
    }

    func runRotateAnimation() {
        let rotateForwardAnimationDuration: TimeInterval = 1
        let rotateBackAnimationDuration: TimeInterval = 1
        let animationDuration: TimeInterval = rotateForwardAnimationDuration + rotateBackAnimationDuration

        UIView.animateKeyframes(withDuration: animationDuration, delay: 0, options: [], animations: { 
            UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: rotateForwardAnimationDuration) {
                self.imageView.transform = CGAffineTransform(rotationAngle: .pi)
            }

            UIView.addKeyframe(withRelativeStartTime: 0.5, relativeDuration: rotateBackAnimationDuration) { 
                self.imageView.transform = .identity 
            }
        }) { (isFinished) in
            // To loop it continuosly, just call the same function from the completion block of the keyframe animation
            self.runRotateAnimation()
        }
    }
}

Answer 2

您可以在 UIView.animate 上呈现的 completionHandler 中执行第二个动画

let duration = self.transitionDuration(using: transitionContext)

let firstAnimDuration = 0.5
UIView.animate(withDuration: firstAnimDuration, animations: {
    /* Do here the first animation */
}) { (completed) in

   let secondAnimDuration = 0.5
   UIView.animate(withDuration: secondAnimDuration, animations: { 
       /* Do here the second animation */
   })
}

现在你可能会遇到另一个问题。

如果您使用 CGAffineTransform 旋转您的视图，并且为每个动画分配一个此类型的新对象到您的 view.transform，您将丢失之前的变换操作

所以，根据这个帖子：How to apply multiple transforms in Swift，你需要concat变换操作

以 2 个动画块为例

这是一个旋转 180 度并在 1 秒后返回原点的示例：

let view = UIView.init(frame: CGRect.init(origin: self.view.center, size: CGSize.init(width: 100, height: 100)))
view.backgroundColor = UIColor.red
self.view.addSubview(view)

var transform = view.transform
transform = transform.rotated(by: 180)

UIView.animate(withDuration: 2, animations: {
    view.transform = transform
}) { (completed) in

    transform = CGAffineTransform.identity
    UIView.animate(withDuration: 2, delay: 1, options: [], animations: { 
        view.transform = transform
    }, completion: nil)
}

.repeat 动画和 .autoreverse 示例

.animate 方法使您能够设置一些动画选项。特别是 UIViewAnimationOptions 包含的结构：

1. .repeat，无限重复你的动画块
2. .autoreverse，将您的视图恢复到原始状态

考虑到这一点，您可以这样做：

var transform = view.transform.rotated(by: 180)
UIView.animate(withDuration: 2, delay: 0, options: [.repeat, .autoreverse], animations: {
     self.myView.transform = transform
})

但是你需要两个动画之间有一个延迟，所以你需要做这个技巧：

递归动画示例和延迟 1 秒

只需在您的 ViewController 中创建一个方法来为您的视图设置动画。在最后一个completionHandler中，只需调用该方法创建一个无限循环。

最后你需要调用 viewDidAppear 上的方法来启动动画。

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    self.animation()
}


func animation() {
    var transform = view.transform
    transform = transform.rotated(by: 180)

    UIView.animate(withDuration: 2, delay: 0, options: [], animations: {

        self.myView.transform = transform

    }) { bool in
        transform = CGAffineTransform.identity

        UIView.animate(withDuration: 2, delay: 1, options: [], animations: {

            self.myView.transform = transform

        }, completion: { bool in
            self.animation()
        })
    }
}