swift - CAShapelayer 未显示

Question

我一直在尝试向我的 View 和按钮添加一个图层，但不知何故该图层根本没有出现。我错过了什么？

class ViewController: UIViewController {

    var button1: CustomButton!

    override func viewDidLoad() {
        super.viewDidLoad()

        button1 = CustomButton(frame: CGRectZero)

        let views1 = ["button1": button1]

        button1.backgroundColor = .clearColor()
        view.addSubview(button1)

        view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-50-[button1(50)]", options: [], metrics: nil, views: views1))
        view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[button1(50)]-50-|", options: [], metrics: nil, views: views1))
    }
}

class CustomButton: UIButton {

    let shape = CAShapeLayer()

    override init(frame: CGRect) {
        super.init(frame: frame)

        translatesAutoresizingMaskIntoConstraints = false

        shape.fillColor = UIColor.redColor().CGColor
        shape.strokeColor = UIColor.blackColor().CGColor
        shape.lineWidth = 0.5

        shape.bounds = CGRect(x: 0, y: 0, width: 50, height: 50)

        layer.insertSublayer(shape, atIndex: 0)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func layoutSubviews() {
        super.layoutSubviews()

        let padding: CGFloat = 10

        let x = frame.origin.x - padding
        let y = frame.origin.y - padding
        let widths = bounds.width  + 2 * padding
        let height = bounds.height + 2 * padding

        let rect = CGRect(x: x, y: y, width: widths, height: height)

        shape.frame = rect
        shape.path = UIBezierPath(rect: rect).CGPath
    }
}

按钮已毫无问题地添加到 View 中，但图层似乎不可见(也尝试在点击时更改颜色等，设置位置或仅编辑图层本身而不添加新图层)。

Answer 1

您错过了“|”在你的约束字符串中。请更新为，

    view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-50-[button1(50)]|", options: [], metrics: nil, views: views1))
    view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|[button1(50)]-50-|", options: [], metrics: nil, views: views1))