带阴影的线圆

Question

我正在尝试用带有阴影的笔触颜色绘制一个空圆圈。

let bezierPath              = UIBezierPath(ovalIn: CGRect(x: 80, y: 200, width: 100, height: 100))

let shapeLayer              = CAShapeLayer()
shapeLayer.path             = bezierPath.cgPath
shapeLayer.fillColor        = UIColor.clear.cgColor
shapeLayer.strokeColor      = UIColor.white.cgColor
shapeLayer.lineWidth        = 3
shapeLayer.shadowPath       = bezierPath.cgPath
shapeLayer.shadowColor      = UIColor.black.cgColor
shapeLayer.shadowOffset     = CGSize(width: 0, height: 0)
shapeLayer.shadowOpacity    = 1

containerView.layer.addSublayer(shapeLayer)

但是阴影填满了整个圆圈。如何去掉它并保留外阴影？

Answer 1

只要省略设置shapeLayer.shadowPath，你会得到这样的东西（图层的标准阴影，基本上是图层的不透明部分）：