Pulse View playground

PulseView.playground

//: Playground - noun: a place where people can play

import UIKit
import PlaygroundSupport

let kStartAlpha: CGFloat = 0.8
let kEndAlpha: CGFloat = 0.0
let kDuration: CFTimeInterval = 1.0

let bgColor = UIColor(red: 153.0/255, green: 192.0/255, blue: 204.0/255, alpha: 1.0)
let pulseColor = UIColor.white.withAlphaComponent(kStartAlpha)

class View: UIView {
    
    override func layoutSubviews() {
        super.layoutSubviews()
        if let sublayers = self.layer.sublayers {
            sublayers.forEach({ (sublayer) in
                sublayer.removeFromSuperlayer()
            })
        }
        
        let center = self.center
        let minRadius = min(center.x, center.y) / 3.0
        let maxRadius = min(center.x, center.y) / 1.5
        
        let innerCircleLayer = drawCircle(center: center, radis: minRadius, color: pulseColor)
        let outerCircleLayer = drawCircle(center: center, radis: minRadius, color: pulseColor)
        
        self.layer.addSublayer(outerCircleLayer)
        self.layer.addSublayer(innerCircleLayer)
        addAnimation(to: outerCircleLayer, center: center, startRadius: minRadius, endRadius: maxRadius)
    }
    
    func drawCircle(center: CGPoint, radis: CGFloat, color: UIColor) -> CAShapeLayer{
        
        let circleLayer = CAShapeLayer()
        circleLayer.path = getCirclePath(center: center, radius: radis).cgPath
        circleLayer.fillColor = color.cgColor
        circleLayer.lineWidth = 0.0
        
        return circleLayer
    }
    
    private func getCirclePath(center: CGPoint, radius: CGFloat) -> UIBezierPath {
        return UIBezierPath(arcCenter: center, radius: radius, startAngle: CGFloat(0), endAngle: CGFloat(M_PI*2), clockwise: true)
    }
    
    private func addAnimation(to layer: CAShapeLayer, center: CGPoint, startRadius: CGFloat, endRadius: CGFloat, startOpacity: CGFloat = kStartAlpha, endOpacity: CGFloat = kEndAlpha, duration: CFTimeInterval = kDuration) {
        
        let startCirclePath = getCirclePath(center: center, radius: startRadius)
        let endCirclePath = getCirclePath(center: center, radius: endRadius)

        let radiusAnimation = CABasicAnimation(keyPath: "path")
        radiusAnimation.fromValue = startCirclePath.cgPath
        radiusAnimation.toValue = endCirclePath.cgPath
        
        let opacityAnimation = CABasicAnimation(keyPath: "opacity")
        opacityAnimation.fromValue = startOpacity
        opacityAnimation.toValue = endOpacity

        let group = CAAnimationGroup()
        group.animations = [radiusAnimation, opacityAnimation]
        group.duration = kDuration
        group.repeatCount = Float(CGFloat.greatestFiniteMagnitude)
        group.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
        group.isRemovedOnCompletion = false
        
        layer.add(group, forKey: "opacityAndRadius")
    }
}

let myAwesomeView = View(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
myAwesomeView.backgroundColor = bgColor
PlaygroundPage.current.liveView = myAwesomeView