iOS 添加 CAShapeLayer 未在运行时显示

Question

我有一个文本字段，从 Storyboard添加，尝试使用 CAShapeLayer 和 BeizerPath 在文本字段底部添加行

extension UITextField {

    func getLine() {
        let x1 = self.frame.origin.x
        let y = self.frame.origin.y + self.frame.size.height
        let start = CGPoint(x: x1, y: y)

        let x2 = self.frame.origin.x + self.frame.size.width
        let end = CGPoint(x: x2, y: y)

        print("\(start) \(end)")

        let path = UIBezierPath()
        path.move(to: start)
        path.addLine(to: end)

        let shapeLayer = CAShapeLayer()
        shapeLayer.path = path.cgPath
        shapeLayer.strokeColor = UIColor.black.cgColor
        shapeLayer.lineWidth = 1.0
        shapeLayer.fillColor = UIColor.clear.cgColor
        self.layer.addSublayer(shapeLayer)
    }
}

用法:txtFiled.getLine()

但它没有显示。让我知道遗漏了什么或做错了什么？

Answer 1

问题出在您对贝塞尔曲线路径的坐标计算中。您正在使用文本字段框架的原点作为您的路径。当您将路径添加到 UITextField 而不是容器时，您应该使用边界原点来计算路径的坐标。更正以下代码:

extension UITextField {

    func getLine() {
        let x1 = self.bounds.origin.x
        let y = self.bounds.origin.y + self.frame.size.height
        let start = CGPoint(x: x1, y: y)

        let x2 = self.bounds.origin.x + self.frame.size.width
        let end = CGPoint(x: x2, y: y)

        print("\(start) \(end)")

        let path = UIBezierPath()
        path.move(to: start)
        path.addLine(to: end)

        let shapeLayer = CAShapeLayer()
        shapeLayer.path = path.cgPath
        shapeLayer.strokeColor = UIColor.black.cgColor
        shapeLayer.lineWidth = 5.0
        shapeLayer.fillColor = UIColor.clear.cgColor
        self.layer.addSublayer(shapeLayer)
    }
}

结帐apple's doc on view programming guide