使用 CABasicAnimation 将半径从 0 调整为 100

Question

我想制作一个圆圈。圆半径应该从 0 增加到 100。我用 transform.scale 动画试过了。但是当然不可能缩放半径为 0 的圆。当我将圆的半径设置为 1 时，圆是可见的，尽管它不应该在动画的开头。最小示例：

let circleShape = CAShapeLayer()

let circlePath = UIBezierPath(arcCenter: .zero, radius: 0, startAngle: CGFloat(0), endAngle: CGFloat(Double.pi*2), clockwise: true)

circleShape.path = circlePath.cgPath
circleShape.fillColor = UIColor.brown.cgColor
let circleAnimation = CABasicAnimation(keyPath: "transform.scale")

circleAnimation.fromValue = 0
circleAnimation.toValue = 100
circleAnimation.duration = 1.9
circleAnimation.beginTime = CACurrentMediaTime() + 1.5
circleShape.add(circleAnimation, forKey: nil)

在动画结束时，半径应保持在新值。

编辑：感谢@Rob mayoff

最终代码：

let circleShape = CAShapeLayer()

let circlePath = UIBezierPath(arcCenter: .zero, radius: 400, startAngle: CGFloat(0), endAngle: CGFloat(Double.pi*2), clockwise: true)

circleShape.path = circlePath.cgPath
circleShape.fillColor = UIColor.brown.cgColor
let circleAnimation = CABasicAnimation(keyPath: "transform.scale")

circleAnimation.fromValue = 0.0000001
circleAnimation.toValue = 1
circleAnimation.duration = 1.9
circleAnimation.beginTime = CACurrentMediaTime() + 1.5
circleShape.add(circleAnimation, forKey: nil)
circleAnimation.fillMode = .backwards

Answer 1

可能您想要做的是将 circlePath 的半径设置为您的最终半径：

let circlePath = UIBezierPath(arcCenter: .zero, radius: 0, startAngle: CGFloat(0), endAngle: CGFloat(Double.pi*2), clockwise: true)
circlePath.clone()

然后从接近零的数字到 1.0 设置动画：

circleAnimation.fromValue = 0.0001
circleAnimation.toValue = 1.0

如果你想让动画在以后开始（通过设置 beginTime），那么你可能还想设置填充模式，以便 fromValue 应用于图层直到动画开始：

circleAnimation.fillMode = .backwards

Answer 2

您应该使用大于 0 的半径。然后您可以使用 circleShape.transform = CATransform3DMakeScale(0.0, 0.0, 0.0) 缩小它在添加图层之前。然后你就可以开始动画了：

        let circleShape = CAShapeLayer()
    let center =  CGPoint(x: view.frame.width / 2, y: view.frame.height / 2)
    let circlePath = UIBezierPath(arcCenter: center, radius: 100.0, startAngle: CGFloat(0), endAngle: CGFloat(Double.pi*2), clockwise: true)
    circleShape.transform = CATransform3DMakeScale(0.0, 0.0, 0.0)

    circleShape.path = circlePath.cgPath
    circleShape.fillColor = UIColor.brown.cgColor
    let circleAnimation = CABasicAnimation(keyPath: "transform.scale")

    circleAnimation.fromValue = 0
    circleAnimation.toValue = 1
    circleAnimation.duration = 5.9
    circleAnimation.beginTime = CACurrentMediaTime() + 1.5
    circleShape.add(circleAnimation, forKey: nil)

    view.layer.addSublayer(circleShape)

使用 CABasicAnimation 将半径从 0 调整为 100

Resize radius from 0 to 100 with CABasicAnimation

swift

swift4