swift跑马灯动画

动画的实现有很多中方式，这里我简单实用三种，分析其中的利弊。

        //  跑马灯动画，此方法简单只需要设置动画的各种册书即可
        var frame = tipLabel?.frame
        frame?.origin.x = screenW
        tipLabel?.frame = frame!

        UIView.beginAnimations("testAnimation", context: nil)
        UIView.setAnimationDuration(3.0)
        UIView.setAnimationCurve(UIView.AnimationCurve.linear)
        UIView.setAnimationDelegate(self)
        UIView.setAnimationRepeatAutoreverses(false)
        UIView.setAnimationRepeatCount(100)

        frame = tipLabel?.frame
        frame?.origin.x = -screenW
        tipLabel?.frame = frame!

        UIView.commitAnimations()

        //  跑马灯动画  此方法代码量最少
        UIView.animate(withDuration: 3, delay: 0, options: UIView.AnimationOptions(rawValue: UIView.AnimationOptions.repeat.rawValue|UIView.AnimationOptions.curveLinear.rawValue), animations: {
            self.tipLabel?.transform = CGAffineTransform(translationX: -(2 * screenW),y: 0)
        }, completion: nil)

第三种方法代码比较多，但是能实现app进入后台在进入前端，动画依然执行。还需要在进入控制器是监听通知。推出时记得移除通知

  //添加监听
        NotificationCenter.default.addObserver(self, selector: #selector(enterBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(becomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)

func configAnimation() {
       // 跑马灯动画 此方法能实现app进入后台在返回前端还能继续运行
        let anim = CABasicAnimation()
        anim.keyPath = "position"
        anim.fromValue = NSValue.init(cgPoint:CGPoint(x: (self.tipLabel?.frame.width)! / 2, y: (self.tipLabel?.frame.origin.y)! + (self.tipLabel?.frame.height)! / 2))
        anim.toValue = NSValue(cgPoint: CGPoint(x: -1 * (self.tipLabel?.frame.width)! / 2, y: (self.tipLabel?.frame.origin.y)! + (self.tipLabel?.frame.height)! / 2))
        anim.duration = 3
        anim.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.linear)
        anim.repeatCount = MAXFLOAT


        let seconedAnim = CABasicAnimation()
        seconedAnim.keyPath = "position"
        seconedAnim.fromValue = NSValue.init(cgPoint:CGPoint(x: (self.tipLabel?.frame.width)! / 2 * 3, y:  (self.tipLabel?.frame.origin.y)! + (self.tipLabel?.frame.height)! / 2))
        seconedAnim.toValue = NSValue(cgPoint: CGPoint(x: (self.tipLabel?.frame.width)! / 2, y: (self.tipLabel?.frame.origin.y)! + (self.tipLabel?.frame.height)! / 2))
        seconedAnim.duration = 3
        seconedAnim.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.linear)
        seconedAnim.repeatCount = MAXFLOAT

        self.tipLabel?.layer.add(anim, forKey: "firstAnim")
        self.seconedLabel?.layer.add(seconedAnim, forKey: "seconedAnim")

        anim.isRemovedOnCompletion = false
        seconedAnim.isRemovedOnCompletion = false
}

func beginAnimation() {
        tipLabel?.layer.timeOffset = 0
        tipLabel?.layer.speed = 1.0
        tipLabel?.layer.beginTime = 0
        
        seconedLabel?.layer.timeOffset = 0
        seconedLabel?.layer.speed = 1.0
        seconedLabel?.layer.beginTime = 0
    }
    
    @objc func enterBackground(){
        let pauseTime = self.tipLabel?.layer.convertTime(CACurrentMediaTime(), to: nil)
        self.tipLabel?.layer.speed = 0
        self.tipLabel?.layer.timeOffset = pauseTime!
        
    }
    
    @objc func becomeActive(){
        self.configAnimation()
        let pauseTime = self.tipLabel?.layer.timeOffset
        self.tipLabel?.layer.speed = 1
        self.tipLabel?.layer.timeOffset = 0
        self.tipLabel?.layer.beginTime = 0
        let timeSincePause = Double((self.tipLabel?.layer.convertTime(CACurrentMediaTime(), from: nil))!) - Double(pauseTime!)
        
        self.seconedLabel?.layer.speed = 1
        self.seconedLabel?.layer.timeOffset = 0
        self.seconedLabel?.layer.beginTime = 0
        self.tipLabel?.layer.beginTime = timeSincePause
        self.seconedLabel?.layer.beginTime = timeSincePause
    }

  移除通知

 deinit {
        NotificationCenter.default.removeObserver(self, name: UIApplication.didEnterBackgroundNotification, object: nil)
        NotificationCenter.default.removeObserver(self, name: UIApplication.didBecomeActiveNotification, object: nil)
    }