ios - 添加图像到 CALayer/CAShapeLayer 总是显示黑色

Question

我想在一个圆形 CAShapeLayer 中添加一个图像，所以我开始像这样创建一个圆圈:

let circleContainer = UIBezierPath(arcCenter: pCenter, radius: radius - 10, startAngle: 0, endAngle: CGFloat(M_PI * 2), clockwise: true)
let imageSubLayer = CAShapeLayer()
imageSubLayer.path = circleContainer.CGPath

self.view.layer.addSublayer(imageSubLayer)

然后添加我做的图像:

let imageLayer = CALayer()
imageLayer.contents = UIImage(named: "pic")?.CGImage
imageSubLayer.addSublayer(imageLayer)

//I've also tried adding the image directly to the circular CAShapeLayer like so but without any success:
imageSubLayer.contents = UIImage(named: "pic")?.CGImage

问题是:当我运行应用程序时，circleContainer 总是显示黑色(见下图)。我究竟做错了什么 ？提前致谢!

Answer 1

您还没有设置imageLayer 的框架。但也不清楚你到底想达到什么目的。如果你想让你的图像遮住你的形状层，你需要将它设置为 imageLayer 的 mask 属性:

let imageLayer = CALayer()
imageLayer.contents = UIImage(named: "pic")?.CGImage
imageLayer.frame = view.bounds
imageLayer.mask = imageSubLayer
view.layer.addSublayer(imageLayer)

更新

如果您在 drawRect 中有此代码，您可以直接绘制到 View 的 CGContext 中。例如:

override func drawRect(rect: CGRect)
{
    super.drawRect(rect)
    let circleRect = CGRectInset(self.bounds, 10, 10)
    let path = UIBezierPath(ovalInRect: circleRect)
    path.lineWidth = 10
    UIColor.yellowColor().set()
    path.stroke()
    path.fill()
    path.addClip()
    let image = UIImage(named: "pic")
    image?.drawInRect(circleRect)
}

上面的代码绘制了一个黄色圆圈，中心的图像被剪裁到圆圈的边界。