Swift version: 5.6
iOS makes it easy to draw shapes using CAShapeLayer
, but you also get the ability to adjust how shapes are drawn. By manipulating the strokeStart
and strokeEnd
properties you can make shapes draw themselves on the screen: you can present a half-drawn star, or a three-quarters drawn circle, for example.
However, as clever as that is what’s really neat is being able to animate the drawing process. To try it out, first create a CAShapeLayer
with a stroke that’s visible, like this one:
let layer = CAShapeLayer()
let bounds = CGRect(x: 50, y: 50, width: 250, height: 250)
layer.path = UIBezierPath(roundedRect: bounds, byRoundingCorners: .allCorners, cornerRadii: CGSize(width: 20, height: 20)).cgPath
layer.strokeColor = UIColor.black.cgColor
layer.fillColor = nil
layer.lineDashPattern = [8, 6]
view.layer.addSublayer(layer)
Now create and add a CABasicAnimation
to adjust the strokeEnd
property:
let animation = CABasicAnimation(keyPath: "strokeEnd")
animation.fromValue = 0
animation.toValue = 1
animation.duration = 2
animation.autoreverses = true
animation.repeatCount = .infinity
layer.add(animation, forKey: "line")
I made that animate from 0 (not drawn) to 1 (fully drawn) over two seconds, but also made it reverse at the end and repeat infinite times.
SAVE 50% To celebrate Black Friday, all our books and bundles are half price, so you can take your Swift knowledge further without spending big! Get the Swift Power Pack to build your iOS career faster, get the Swift Platform Pack to builds apps for macOS, watchOS, and beyond, or get the Swift Plus Pack to learn advanced design patterns, testing skills, and more.
Sponsor Hacking with Swift and reach the world's largest Swift community!
Available from iOS 3.2
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Link copied to your pasteboard.