java button 圆角_UIButton具有渐变边框和圆角

我想要的是一个自定义UIButton，它有一个渐变边框(只是边框是渐变)和圆角 . 我几乎到了我想去的地方，但是角落有问题 . 这是我目前拥有的：

这是我的代码：

override func viewDidLoad() {

super.viewDidLoad()

let gradient = CAGradientLayer()

gradient.frame = CGRect(origin: CGPoint.zero, size: self.myButton.frame.size)

gradient.colors = [UIColor.blue.cgColor, UIColor.green.cgColor]

gradient.startPoint = CGPoint(x: 0.0, y: 0.5)

gradient.endPoint = CGPoint(x: 1.0, y: 0.5)

gradient.cornerRadius = 15

let shape = CAShapeLayer()

shape.lineWidth = 5

shape.path = UIBezierPath(rect: self.myButton.bounds).cgPath

shape.strokeColor = UIColor.black.cgColor

shape.fillColor = UIColor.clear.cgColor

shape.cornerRadius = 15

gradient.mask = shape

self.myButton.clipsToBounds = true

self.myButton.layer.cornerRadius = 15

self.myButton.layer.addSublayer(gradient)

}

所以问题是我如何用渐变显示角落？