带有部分边框的 UIView 边框

Question

我有 UIView，我只需要绘制一个边框部分视图，如何使用 UIBezierPath

Answer 1

如果你想使用UIBezierPath，你可以选择“愚蠢”的方式：

画满您的视图边框
通过在边框顶部绘制一个矩形，用视图的背景颜色“掩盖”您不希望边框存在的部分。

class MyView: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    
    private func commonInit() {
        layer.cornerRadius = 3
        backgroundColor = .white
        layer.masksToBounds = true
    }
    
    override func draw(_ rect: CGRect) {
        let borderPath = UIBezierPath(roundedRect: bounds, cornerRadius: 3)
        borderPath.lineWidth = 7
        UIColor.gray.setStroke()
        borderPath.stroke()
        let covering = UIBezierPath(rect: CGRect(x: 20, y: -10, width: self.bounds.width - 40, height: 20))
        backgroundColor?.setFill()
        covering.fill()
    }
}

输出：

除此之外，我想不出一个简单的方法来做到这一点。

但是，如果您可以使用 CAShapeLayer...

您应该将 CAShapeLayer 的 strokeEnd and strokeStart 属性设置为视图层的子层。

示例：

class MyView: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    
    private func commonInit() {
        layer.cornerRadius = 3
        let border = CAShapeLayer()
        // make sure this path coincides with the border of the view
        border.path = UIBezierPath(roundedRect: bounds, cornerRadius: 3).cgPath

        // you should tweak these numbers
        border.strokeStart = 0.3
        border.strokeEnd = 0.7

        border.strokeColor = UIColor.gray.cgColor
        border.lineWidth = 3
        border.fillColor = nil
        layer.addSublayer(border)
        backgroundColor = .white
    }
}

输出：

Answer 2

我做了完全相同的事情，但做了一次动画，以模仿 android 材料文本字段设计和 ios 应用程序中的行为这里是形状创建代码：

placeholderWidth 是顶部间隙的大小，leftInset 从框架左角插入

class FloatingTextfieldBorderShapeCreator {
    
    var leftInset: CGFloat

    init(leftInset: CGFloat) {
        self.leftInset = leftInset
    }

    func create(frame: CGRect, placeholderWidth: CGFloat) -> CGPath {
        let path = UIBezierPath()
        let arcRadius: CGFloat = 4.0
    
        //1. starting point top left
        let startingPoint = CGPoint(x: frame.minX + leftInset - 4, y: frame.minY)
        path.move(to: startingPoint)
    
        //2. top left arc
        let topLeftArcCenter = CGPoint(x: frame.minX + arcRadius, y: arcRadius)
        path.addArc(withCenter: topLeftArcCenter, radius: arcRadius, startAngle: 3*CGFloat.pi/2, endAngle: CGFloat.pi, clockwise: false)
    
        //3. left line
        let leftLineEndPoint = CGPoint(x: frame.minX, y: frame.height - arcRadius)
        path.addLine(to: leftLineEndPoint)
    
        //4. bottom left arc
        let bottomLeftArcCenter = CGPoint(x: frame.minX + arcRadius, y: frame.height - arcRadius)
        path.addArc(withCenter: bottomLeftArcCenter, radius: arcRadius, startAngle: CGFloat.pi, endAngle: CGFloat.pi/2, clockwise: false)
    
        //5. bottom line
        let bottomLineEndPoint = CGPoint(x: frame.width - arcRadius, y: frame.height)
        path.addLine(to: bottomLineEndPoint)
    
        //6. bottom right arc
        let bottomRightArcCenter = CGPoint(x: frame.width - arcRadius, y: frame.height - arcRadius)
        path.addArc(withCenter: bottomRightArcCenter, radius: arcRadius, startAngle: CGFloat.pi/2, endAngle: 0, clockwise: false)
    
        //7. right line
        let rightLineEndPoint = CGPoint(x: frame.width, y: frame.minY + arcRadius)
        path.addLine(to: rightLineEndPoint)
    
        //8. top right arc
        let topRightArcCenter = CGPoint(x: frame.width - arcRadius, y: frame.minY + arcRadius)
        path.addArc(withCenter: topRightArcCenter, radius: arcRadius, startAngle: 0, endAngle: -CGFloat.pi/2, clockwise: false)
    
        //9. top line
        let topLineEndPointX = startingPoint.x + placeholderWidth
        let topLineEndPoint = CGPoint(x: topLineEndPointX, y: frame.minY)
        path.addLine(to: topLineEndPoint)
    
        return path.cgPath
    }
}

要应用于绘图层的属性：

    borderLayer.frame = borderFrame
    borderLayer.fillColor = nil
    borderLayer.lineWidth = 1.0
    borderLayer.strokeColor = .lightGray

带有部分边框的 UIView 边框

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