如何从swift中的图像创建循环加载程序

首先我要感谢@Carpsen90对我的帮助,尽管他的答案不是我想要的,但它帮助我理解了如何使用 CABasicAnimation this answer 我找到了一个解决我的问题的方法,使用图像和 CAShapeLayer

// countdownGlow is the glow (white and red part of my image)
func animateMask() {
        let arcPath = CGMutablePath()
        arcPath.move(to: CGPoint(x: self.countdownGlow.frame.width / 2, y: 0))
        arcPath.addArc(center: CGPoint(x: self.countdownGlow.frame.width / 2, y: self.countdownGlow.frame.width / 2), radius: self.countdownGlow.frame.width / 2, startAngle: CGFloat(-1 * Double.pi / 2), endAngle: CGFloat(-3 * Double.pi / 2), clockwise: false)
        arcPath.addArc(center: CGPoint(x: self.countdownGlow.frame.width / 2, y: self.countdownGlow.frame.width / 2), radius: self.countdownGlow.frame.width / 2, startAngle: CGFloat(-3 * Double.pi / 2), endAngle: CGFloat(-5 * Double.pi / 2), clockwise: false)
        let ringLayer = CAShapeLayer(layer: self.countdownGlow.layer)
        ringLayer.path = arcPath
        
        ringLayer.strokeEnd = 0.0
        ringLayer.fillColor = UIColor.clear.cgColor
        ringLayer.strokeColor = UIColor.black.cgColor
        ringLayer.lineWidth = self.countdownGlow.frame.width / 2
        
        self.countdownGlow.layer.mask = ringLayer
        self.countdownGlow.layer.mask?.frame = self.countdownGlow.layer.bounds
        
        let swipe = CABasicAnimation(keyPath: "strokeEnd")
        swipe.duration = 3
        swipe.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
        swipe.fillMode = kCAFillModeForwards
        swipe.isRemovedOnCompletion = true
        swipe.toValue = 1.0
        ringLayer.add(swipe, forKey: "strokeEnd")
}

我似乎不能简单地告诉我的弧是一个完整的圆,所以我去了半个圆一次,然后另一个半圆的结果

如果您有任何改进,我很乐意尝试一下,因为我相信我的解决方案是没有优化的