Animation keeps the original image at the end - ios

Question

I want to create an animation of a circle disappearing and I did the following code (based on other codes which I found on internet).
class CircleView: UIView {
private var circleLayer: CAShapeLayer?
override init(frame: CGRect) {
super.init(frame: frame)
self.commonInit()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.commonInit()
}
func commonInit() {
self.tintColor = UIColor.lightGrayColor()
self.backgroundColor = UIColor.clearColor()
}
override func drawRect(rect: CGRect) {
super.drawRect(rect)
self.drawCircle()
self.addCircleAnimation()
}
func drawCircle() {
let size:CGFloat = CGFloat(100)
self.circleLayer?.removeFromSuperlayer()
self.circleLayer = CAShapeLayer()
self.circleLayer?.frame = self.bounds
let radius = size / 2;
let path = UIBezierPath(arcCenter: CGPointMake(size / 2, size / 2), radius: radius, startAngle: -CGFloat(M_PI) / 4, endAngle: 2 * CGFloat(M_PI) - CGFloat(M_PI) / 4, clockwise: true)
self.circleLayer?.path = path.CGPath
self.circleLayer?.fillColor = UIColor.clearColor().CGColor
self.circleLayer?.strokeColor = self.tintColor.CGColor
self.circleLayer?.lineWidth = CGFloat(2.0)
self.circleLayer?.rasterizationScale = 2.0 * UIScreen.mainScreen().scale
self.circleLayer?.shouldRasterize = true
self.layer.addSublayer(self.circleLayer!)
}
func addCircleAnimation() {
let animation = CABasicAnimation(keyPath: "strokeStart")
animation.fromValue = 0.0
animation.toValue = 1.0
animation.duration = CFTimeInterval(floatLiteral: 1)
animation.removedOnCompletion = false
animation.fillMode = kCAFillModeBackwards
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
animation.beginTime = CACurrentMediaTime()
animation.delegate = self
self.circleLayer?.addAnimation(animation, forKey:"strokeStart")
}
}
However when the animation finishes it leaves the original circle, even if I detect with animationDidStop it still has an effect of flickering. What's wrong with this code?

Answer 1

Code to remove circle layer:
class CircleView: UIView {
private var circleLayer: CAShapeLayer?
override init(frame: CGRect) {
super.init(frame: frame)
self.commonInit()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.commonInit()
}
func commonInit() {
self.tintColor = UIColor.lightGrayColor()
self.backgroundColor = UIColor.clearColor()
}
override func drawRect(rect: CGRect) {
super.drawRect(rect)
self.drawCircle()
self.addCircleAnimation()
}
override func animationDidStop(anim: CAAnimation, finished flag: Bool)
{
self.circleLayer?.removeFromSuperlayer()
}
func drawCircle() {
let size:CGFloat = CGFloat(100)
self.circleLayer?.removeFromSuperlayer()
self.circleLayer = CAShapeLayer()
self.circleLayer?.frame = self.bounds
let radius = size / 2;
let path = UIBezierPath(arcCenter: CGPointMake(size / 2, size / 2), radius: radius, startAngle: -CGFloat(M_PI) / 4, endAngle: 2 * CGFloat(M_PI) - CGFloat(M_PI) / 4, clockwise: true)
self.circleLayer?.path = path.CGPath
self.circleLayer?.fillColor = UIColor.clearColor().CGColor
self.circleLayer?.strokeColor = self.tintColor.CGColor
self.circleLayer?.lineWidth = CGFloat(2.0)
self.circleLayer?.rasterizationScale = 2.0 * UIScreen.mainScreen().scale
self.circleLayer?.shouldRasterize = true
self.layer.addSublayer(self.circleLayer!)
}
/** UPDATED. Add animation for strokEnd instead of strokeStart **/
func addCircleAnimation() {
let animation = CABasicAnimation(keyPath: "strokeEnd")
animation.delegate = self
animation.fromValue = 0.0
animation.toValue = 1.0
animation.duration = CFTimeInterval(floatLiteral: 1)
animation.removedOnCompletion = false
animation.fillMode = kCAFillModeBackwards
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
animation.beginTime = CACurrentMediaTime()
animation.delegate = self
self.circleLayer?.addAnimation(animation, forKey:"strokeEnd")
}
}