Попробуйте использовать CAReplicatorLayer и задержку экземпляра, чтобы синхронизировать все. Вот детская площадка. Я не уверен на 100%, что вы хотите, но это должно быть близко.
//: A UIKit based Playground for presenting user interface
import UIKit
import PlaygroundSupport
class MyIndicator: UIView {
let gap = CGFloat(.pi/4 / 6.0)
private var replicatorLayer = CAReplicatorLayer()
private var mainShapeLayer = CAShapeLayer()
override init(frame: CGRect) {
super.init(frame: frame)
commonSetup()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonSetup()
}
func commonSetup(){
mainShapeLayer = CAShapeLayer()
mainShapeLayer.frame = self.bounds
mainShapeLayer.fillColor = UIColor.clear.cgColor
mainShapeLayer.lineWidth = 6.8
mainShapeLayer.strokeColor = UIColor.blue.cgColor
let startAngle:CGFloat = CGFloat(Double.pi * 2) + gap/2
let endAngle:CGFloat = startAngle + CGFloat(Double.pi/2) - gap/2
mainShapeLayer.path = UIBezierPath(arcCenter: center, radius: self.bounds.midX - 10, startAngle: startAngle, endAngle: endAngle, clockwise: true).cgPath
replicatorLayer = CAReplicatorLayer()
replicatorLayer.frame = self.bounds
replicatorLayer.instanceCount = 4
let angle = (Double.pi * 2)/4
replicatorLayer.instanceTransform = CATransform3DRotate(CATransform3DIdentity, CGFloat(angle), 0, 0, 1)
replicatorLayer.addSublayer(mainShapeLayer)
replicatorLayer.opacity = 0
self.layer.addSublayer(replicatorLayer)
}
func animate(){
let defaultDuration : Double = 0.75
let animate = CAKeyframeAnimation(keyPath: "opacity")
animate.values = [1, 0.3, 1]
animate.keyTimes = [0, 0.5, 1]
animate.repeatCount = .greatestFiniteMagnitude
animate.duration = defaultDuration
animate.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
replicatorLayer.instanceDelay = defaultDuration/4
self.mainShapeLayer.add(animate, forKey: nil)
let opacityIn = CABasicAnimation(keyPath: "opacity")
opacityIn.fromValue = 1
opacityIn.toValue = 0
opacityIn.duration = 0.2
replicatorLayer.add(opacityIn, forKey: nil)
self.replicatorLayer.opacity = 1
}
func stopAnimating(){
CATransaction.begin()
let opacityOut = CABasicAnimation(keyPath: "opacity")
opacityOut.fromValue = 1
opacityOut.toValue = 0
opacityOut.duration = 0.2
CATransaction.setCompletionBlock {
[weak self] in
self?.mainShapeLayer.removeAllAnimations()
}
replicatorLayer.add(opacityOut, forKey: nil)
self.replicatorLayer.opacity = 0
CATransaction.commit()
}
override func layoutSubviews() {
super.layoutSubviews()
mainShapeLayer.frame = self.bounds
replicatorLayer.frame = self.bounds
}
}
class MyViewController : UIViewController {
override func loadView() {
let view = UIView()
view.backgroundColor = .white
let indicator = MyIndicator(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
indicator.animate()
//just to simulate starting and stoping
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 10) {
indicator.stopAnimating()
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 5) {
indicator.animate()
}
}
view.addSubview(indicator)
self.view = view
}
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()