Question

我有一个由UIViewPropertyAnimator驱动的可中断过渡，我想为沿其目的地的非线性路径设置视图动画。

进行一些研究，我发现执行此操作的方法是使用： CAKeyframeAnimation。但是，我在协调动画方面遇到问题，在CAKeyframeAnimation填充模式方面也遇到问题。即使我将其设置为前进，它也似乎是反向的。

下面是贝塞尔曲线路径：

let bezierPath = self.generateCurve(from: CGPoint(x: self.itemStartFrame.midX, y: self.itemStartFrame.midY), to: CGPoint(x: self.itemEndFrame.midX, y: self.itemEndFrame.midY), bendFactor: 1, thickness: 1)

func generateCurve(from: CGPoint, to: CGPoint, bendFactor: CGFloat, thickness: CGFloat) -> UIBezierPath {

    let center = CGPoint(x: (from.x+to.x)*0.5, y: (from.y+to.y)*0.5)
    let normal = CGPoint(x: -(from.y-to.y), y: (from.x-to.x))
    let normalNormalized: CGPoint = {
        let normalSize = sqrt(normal.x*normal.x + normal.y*normal.y)
        guard normalSize > 0.0 else { return .zero }
        return CGPoint(x: normal.x/normalSize, y: normal.y/normalSize)
    }()

    let path = UIBezierPath()

    path.move(to: from)

    let midControlPoint: CGPoint = CGPoint(x: center.x + normal.x*bendFactor, y: center.y + normal.y*bendFactor)
    let closeControlPoint: CGPoint = CGPoint(x: midControlPoint.x + normalNormalized.x*thickness*0.5, y: midControlPoint.y + normalNormalized.y*thickness*0.5)
    let farControlPoint: CGPoint = CGPoint(x: midControlPoint.x - normalNormalized.x*thickness*0.5, y: midControlPoint.y - normalNormalized.y*thickness*0.5)


    path.addQuadCurve(to: to, controlPoint: closeControlPoint)
    path.addQuadCurve(to: from, controlPoint: farControlPoint)
    path.close()
    return path
}

路径可视化：

let shapeLayer = CAShapeLayer()
shapeLayer.path = bezierPath.cgPath
shapeLayer.strokeColor = UIColor.red.cgColor
shapeLayer.lineWidth = 2
containerView.layer.addSublayer(shapeLayer)

这是CAKeyframeAnimation，它位于UIViewPropertyAnimator中

let curvedPathAnimation = CAKeyframeAnimation(keyPath: "position")
curvedPathAnimation.path = bezierPath.cgPath
curvedPathAnimation.fillMode = kCAFillModeForwards
curvedPathAnimation.calculationMode = kCAAnimationPaced
curvedPathAnimation.duration = animationDuration
self.attatchmentView.layer.add(curvedPathAnimation, forKey: nil)

到目前为止，此动画沿正确的路径进行，但是该动画会返回到其初始位置，并且与属性动画师不同步。

有什么建议吗？

使用UIViewPropertyAnimator沿弯曲路径驱动动画？

0 个答案: