一个小小的动画，太阳公公上山又下山。先上效果图。

 

用 lipecap 录的gif效果有点卡顿。好吧，说下如何实现的。

首先在一个大圆内先计算出内切九边形各个顶点的位置，接着连接相应的顶点变成一个九角星太阳的九条光芒，然后在九角星的中心画一个圈形的Layer，这样就大致画好了大阳的形状。

新建一个叫SunView的文件继承自UIView，然后在init方法内添加一个addSunLayer()的方法。并在里面添加以下方内容

class SunView: UIView {

        override init(frame: CGRect) {

        super.init(frame: frame)

        addSunLayer()

    }

 

    required init?(coder aDecoder: NSCoder) {

        super.init(coder: aDecoder)

    }

}

在addSunLayer()方法内添加绘制九角星的代码：

let ninePolyganPath:UIBezierPath = UIBezierPath()
//大圆的半径        
let radius:CGFloat = self.frame.size.width / 2
//九角星各个顶点的位置        
var anglePoints:Dictionary<String,CGPoint> = Dictionary<String,CGPoint>()
//第一个顶点的位置，最右边中间那个点        
let firstPoint:CGPoint = CGPoint(x: bounds.width, y: bounds.width / 2)
anglePoints["0"] = firstPoint
ninePolyganPath.moveToPoint(firstPoint)
        
 for i in 1..<9 {
    //将圆分成9份，每一份的大小为40度
    let angle = Double(i) * 40.0 
    //算出相应角度的三角函数值
    let rateSin:CGFloat = sin(CGFloat(angle / 180 * M_PI))
    let rateCos:CGFloat = cos(CGFloat(angle / 180 * M_PI))
    let x:CGFloat = radius * rateCos + radius
    let y:CGFloat = radius * rateSin + radius
    anglePoints[String(i)] = CGPoint(x: x, y: y)        
 }
//连接相应的九个点，使之成为九角星
ninePolyganPath.addLineToPoint(anglePoints["4"]!)
ninePolyganPath.addLineToPoint(anglePoints["8"]!)
ninePolyganPath.addLineToPoint(anglePoints["3"]!) ninePolyganPath.addLineToPoint(anglePoints["7"]!) ninePolyganPath.addLineToPoint(anglePoints["2"]!)
ninePolyganPath.addLineToPoint(anglePoints["6"]!)
ninePolyganPath.addLineToPoint(anglePoints["1"]!)
ninePolyganPath.addLineToPoint(anglePoints["5"]!)
ninePolyganPath.closePath()
        
let ninePolyganLayer:CAShapeLayer = CAShapeLayer()
ninePolyganLayer.fillColor = UIColor.yellowColor().CGColor
ninePolyganLayer.strokeColor = UIColor.yellowColor().CGColor
ninePolyganLayer.lineWidth = 5
ninePolyganLayer.path = ninePolyganPath.CGPath

   self.layer.addSublayer(ninePolyganLayer)

 在ViewContoller文件内添加以下代码：

  let sunView = SunView(frame: CGRect(x: 100, y: 100, width: 100, height: 100))

  self.view.addSubview(sunView)

此时九角星就做好了，运行的效果如下：

接着要在九角星的中星心位置添加一个圆，做为太阳中心。添加一个计算属性，一个钜形的内切圆路径。

var sunCirclePath:UIBezierPath {
        return UIBezierPath(ovalInRect: CGRect(x: self.frame.size.width * 0.3 / 2, y: self.frame.size.height * 0.3 / 2, width: self.frame.size.width - self.frame.size.width * 0.3, height: self.frame.size.height - self.frame.size.height * 0.3))
 }

 接着在addSunLayer方法内添加以下内容：

let sunLayer:CAShapeLayer = CAShapeLayer()
sunLayer.path = sunCirclePath.CGPath
sunLayer.lineWidth =  5
sunLayer.fillColor = UIColor.yellowColor().CGColor
sunLayer.strokeColor = UIColor.colorWithHexString("#eecc00").CGColor
self.layer.addSublayer(sunLayer)

//让太阳转动起来

  let animation:CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation")

  animation.fromValue = 0.0

  animation.toValue = 2 * M_PI

  animation.duration = 5

  animation.repeatCount = HUGE 

  layer.addAnimation(animation, forKey: nil)

 并将上面ninePolyganLayer添加到图层的代码做如下修改。

self.layer.insertSublayer(ninePolyganLayer, below: sunLayer)

 //self.layer.addSublayer(ninePolyganLayer)

此时运行效果如下：

最后就是让sunView按着指定的路径运行就可以了。回到ViewController文件内，添加以下计算路径属性，画出一条弧形路径，然后让太阳按着这个路径移动。

var sunrisePath:UIBezierPath {
        let path:UIBezierPath = UIBezierPath()
        path.moveToPoint(CGPoint(x: 0, y: 160))
        path.addQuadCurveToPoint(CGPoint(x: self.view.frame.size.width, y: 160), controlPoint: CGPoint(x: self.view.frame.size.width / 2, y: 60))
        //path.closePath() //这个不能用，
        return path
 }

 添加以下动画代码

let sunriseAnimation:CAKeyframeAnimation = CAKeyframeAnimation(keyPath: "position")
sunriseAnimation.path = sunrisePath.CGPath
sunriseAnimation.duration = 3
sunriseAnimation.calculationMode = kCAAnimationPaced
sunriseAnimation.fillMode = kCAFillModeForwards
sunriseAnimation.repeatCount = HUGE
sunriseAnimation.removedOnCompletion = false
sunView.layer.addAnimation(sunriseAnimation, forKey: nil)

 这样就完成了。以上仅供参考，还请大家多提意见。