🐷 效果

QQ20170522-160622-HD.gif

🐥 代码

/// ViewController.swift
import UIKit

class ViewController: UIViewController {
  
  lazy var roundView: RoundedView = {
    let v = RoundedView()
    v.backgroundColor = .blue
    v.frame = CGRect(x: 100, y: 100, width: 50, height: 50)
    v.layer.addSublayer(self.radarLayer)
    return v
  }()
  let radarLayer: RadarLayer = {
    let l = RadarLayer()
    l.repeatTime = 3.0
    l.radius = 26
    l.backgroundColor = UIColor.red.cgColor
    l.position = CGPoint(x: 25, y: 25)
    return l
  }()
  
  override func viewDidLoad() {
    super.viewDidLoad()
    view.addSubview(roundView)
  }
}

class RoundedView: UIView {
  override func layoutSubviews() {
    super.layoutSubviews()
    let radius: CGFloat = self.bounds.size.height / 2.0
    self.layer.cornerRadius = radius
//    self.clipsToBounds = true
  }
}


/// RadarLayer.swift
import Foundation
import UIKit
import QuartzCore

class RadarLayer: CALayer {
  
  //MARK: - variables
  var radius: CGFloat = 10 {
    didSet {
      let width = radius * 2
      let position = self.position
      self.bounds = CGRect(x: 0, y: 0, width: width, height: width)
      self.cornerRadius = radius
      self.position = position
    }
  }
  var repeatTime: TimeInterval = 4
  var delayTime: TimeInterval = 0
  var animationGroup: CAAnimationGroup?
  
  //MARK: - life cycle
  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
  override init() {
    super.init()
    contentsScale = UIScreen.main.scale
    opacity = 0
    backgroundColor = UIColor.white.cgColor
    DispatchQueue.global(qos: .default).async {
      self.setupAnimation()
      if self.delayTime != TimeInterval.infinity {
        DispatchQueue.main.async {
          self.add(self.animationGroup!, forKey: "pulse")
        }
      }
    }
  }
  
  func setupAnimation() {
    let defaultCurve = CAMediaTimingFunction(name: kCAMediaTimingFunctionDefault)
    self.animationGroup = CAAnimationGroup()
    self.animationGroup?.duration = self.repeatTime + self.delayTime
    self.animationGroup?.repeatCount = Float.infinity
    self.animationGroup?.isRemovedOnCompletion = false
    self.animationGroup?.timingFunction = defaultCurve
    
    let scaleAnimation = CABasicAnimation(keyPath: "transform.scale.xy")
    scaleAnimation.fromValue = 0.0
    scaleAnimation.toValue = 1.2
    scaleAnimation.duration = self.repeatTime
    
    let opacityAnimation = CAKeyframeAnimation(keyPath: "opacity")
    opacityAnimation.duration = self.repeatTime
    opacityAnimation.values = [0.2, 0.45, 0.5, 0]
    opacityAnimation.keyTimes = [0, 0.20, 0.6, 1]
    opacityAnimation.isRemovedOnCompletion = false
    
    let animations = [scaleAnimation, opacityAnimation]
    self.animationGroup?.animations = animations
  }
  
}