Использование CoreAnimation для анимации положения красной точки на основе пути предполагает, что путь не меняется. Теоретически вы можете определить спиральный путь, который отражает расширяющийся круг. Лично я бы просто использовал CADisplayLink
, специальный таймер, оптимально разработанный для обновления экрана, и полностью отказался от вызовов CoreAnimation. Например,
func startDisplayLink() {
let displayLink = CADisplayLink(target: self, selector: #selector(handleDisplayLink(_:)))
displayLink.add(to: .main, forMode: .common)
}
@objc func handleDisplayLink(_ displayLink: CADisplayLink) {
let percent = CGFloat(displayLink.timestamp).truncatingRemainder(dividingBy: duration) / duration
let radius = ...
let center = containerView.bounds.center
circleLayer.path = makeArcPath(arcCenter: center, radius: radius)
let angle = percent * .pi * 2
let dotCenter = CGPoint(x: center.x + cos(angle) * radius, y: center.y + sin(angle) * radius)
redDot.path = makeArcPath(arcCenter: dotCenter, radius: 5)
}
Это дает:
Полный пример:
class ViewController: UIViewController {
private let radiusRange: ClosedRange<CGFloat> = 10...100
private let duration: CGFloat = 1.5
private lazy var containerView: UIView = {
let containerView = UIView()
containerView.translatesAutoresizingMaskIntoConstraints = false
return containerView
}()
private lazy var redDot: CAShapeLayer = {
let layer = CAShapeLayer()
layer.fillColor = UIColor.red.cgColor
return layer
}()
private lazy var circleLayer: CAShapeLayer = {
let layer = CAShapeLayer()
layer.lineWidth = 1.5
layer.strokeColor = UIColor.black.cgColor
layer.fillColor = UIColor.clear.cgColor
return layer
}()
private weak var displayLink: CADisplayLink?
override func viewDidLoad() {
super.viewDidLoad()
setup()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
startDisplayLink()
}
override func viewDidDisappear(_ animated: Bool) {
super.viewDidDisappear(animated)
stopDisplayLink()
}
}
// MARK: Private utility methods
private extension ViewController {
func setup() {
addContainer()
containerView.layer.addSublayer(circleLayer)
containerView.layer.addSublayer(redDot)
}
func addContainer() {
view.addSubview(containerView)
NSLayoutConstraint.activate([
containerView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
containerView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
containerView.topAnchor.constraint(equalTo: view.topAnchor),
containerView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
])
}
func makeArcPath(arcCenter: CGPoint, radius: CGFloat) -> CGPath {
UIBezierPath(arcCenter: arcCenter, radius: radius, startAngle: 0, endAngle: .pi * 2, clockwise: true).cgPath
}
}
// MARK: - DisplayLink related methods
private extension ViewController {
func startDisplayLink() {
stopDisplayLink() // stop existing display link, if any
let displayLink = CADisplayLink(target: self, selector: #selector(handleDisplayLink(_:)))
displayLink.add(to: .main, forMode: .common)
self.displayLink = displayLink
}
func stopDisplayLink() {
displayLink?.invalidate()
}
@objc func handleDisplayLink(_ displayLink: CADisplayLink) {
let percent = CGFloat(displayLink.timestamp).truncatingRemainder(dividingBy: duration) / duration
let radius = radiusRange.percent(percent)
let center = containerView.bounds.center
circleLayer.path = makeArcPath(arcCenter: center, radius: radius)
let angle = percent * .pi * 2
let dotCenter = CGPoint(x: center.x + cos(angle) * radius, y: center.y + sin(angle) * radius)
redDot.path = makeArcPath(arcCenter: dotCenter, radius: 5)
}
}
// MARK: - CGRect extension
extension CGRect {
var center: CGPoint { return CGPoint(x: midX, y: midY) }
}
// MARK: - ClosedRange extension
extension ClosedRange where Bound: FloatingPoint {
func percent(_ percent: Bound) -> Bound {
(upperBound - lowerBound) * percent + lowerBound
}
}