在 textview 或标签周围快速绘制边框

Question

myLabel.layer.borderWidth = 0.5
myLabel.layer.borderColor = UIColor.green.cgColor

这是绘制边框的简单答案。但是问题是我只需要在右侧和底部绘制边框。我还需要另一个标签在顶部和右侧绘制边框。如何在特定边上绘制边框，而不是所有 4 个边？

Answer 1

添加一个形状图层并在该图层中绘制线条。请注意，图层不参与自动布局，因此您需要将代码放在 viewDidLayoutSubviews 或子类 uilabel 中，并在布局 subview 中执行此操作。这是一个使用 UILabel 子类的 Playground 示例:

    import PlaygroundSupport
    import UIKit
    class L: UILabel {
        var strokeColor = UIColor.blue
        var strokeWidth = CGFloat(0.5)
        private lazy var labelBorderLayer:CAShapeLayer = {
            let shapeLayer = CAShapeLayer()
            self.layer.addSublayer(shapeLayer)
            return shapeLayer
        }()
        override func layoutSubviews() {
            super.layoutSubviews()
            let path = CGMutablePath()
            path.move(to: CGPoint(x: 0, y: bounds.size.height))
            path.addLine(to: CGPoint(x:  bounds.size.width, y: bounds.size.height))
            path.addLine(to: CGPoint(x:  bounds.size.width, y: 0))
            labelBorderLayer.path = path
            labelBorderLayer.strokeColor = strokeColor.cgColor
            labelBorderLayer.lineWidth = strokeWidth
            labelBorderLayer.fillColor = UIColor.clear.cgColor
        }
    }

    let v = UIView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
    let l = L(frame: v.frame.insetBy(dx: 50, dy: 80))
    v.addSubview(l)
    l.textColor = .white
    l.textAlignment = .center
    l.text = "gjgkjgjgjgj"
    v.backgroundColor = .red
    PlaygroundPage.current.liveView = v