仅显示 UIView 的角点

如何只显示 UIView 的角点？

        let view = UIView()
        view.layer.borderColor = UIColor.white.cgColor

        view.layer.borderWidth = 2 
           let maskframe = UIView(frame: CGRect(x:0, y:0, 
          width:view.frame.width, height:view.frame.height))

         view.layer.mask = maskframe.layer.`

这仅掩盖了右边缘，我也不明白它是如何工作的。

尝试用这个class，这里我使用自定义视图绘图CoreGraphics，添加了一些 Inspectable 变量来帮助定制

//
//  CornerView.swift
//  CornersViewSO
//
//  Created by Reinier Melian on 5/31/17.
//  Copyright © 2017 Reinier Melian. All rights reserved.
//

import UIKit
import CoreGraphics

@IBDesignable
class CornerView: UIView {

    @IBInspectable
    var sizeMultiplier : CGFloat = 0.2{
        didSet{
            self.draw(self.bounds)
        }
    }

    @IBInspectable
    var lineWidth : CGFloat = 2{
        didSet{
            self.draw(self.bounds)
        }
    }

    @IBInspectable
    var lineColor : UIColor = UIColor.black{
        didSet{
            self.draw(self.bounds)
        }
    }


    override init(frame: CGRect) {
        super.init(frame: frame)
        self.backgroundColor = UIColor.clear
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.backgroundColor = UIColor.clear
    }

    func drawCorners()
    {
        let currentContext = UIGraphicsGetCurrentContext()

        currentContext?.setLineWidth(lineWidth)
        currentContext?.setStrokeColor(lineColor.cgColor)

        //first part of top left corner
        currentContext?.beginPath()
        currentContext?.move(to: CGPoint(x: 0, y: 0))
        currentContext?.addLine(to: CGPoint(x: self.bounds.size.width*sizeMultiplier, y: 0))
        currentContext?.strokePath()

        //top rigth corner
        currentContext?.beginPath()
        currentContext?.move(to: CGPoint(x: self.bounds.size.width - self.bounds.size.width*sizeMultiplier, y: 0))
        currentContext?.addLine(to: CGPoint(x: self.bounds.size.width, y: 0))
        currentContext?.addLine(to: CGPoint(x: self.bounds.size.width, y: self.bounds.size.height*sizeMultiplier))
        currentContext?.strokePath()

        //bottom rigth corner
        currentContext?.beginPath()
        currentContext?.move(to: CGPoint(x: self.bounds.size.width, y: self.bounds.size.height - self.bounds.size.height*sizeMultiplier))
        currentContext?.addLine(to: CGPoint(x: self.bounds.size.width, y: self.bounds.size.height))
        currentContext?.addLine(to: CGPoint(x: self.bounds.size.width - self.bounds.size.width*sizeMultiplier, y: self.bounds.size.height))
        currentContext?.strokePath()

        //bottom left corner
        currentContext?.beginPath()
        currentContext?.move(to: CGPoint(x: self.bounds.size.width*sizeMultiplier, y: self.bounds.size.height))
        currentContext?.addLine(to: CGPoint(x: 0, y: self.bounds.size.height))
        currentContext?.addLine(to: CGPoint(x: 0, y: self.bounds.size.height - self.bounds.size.height*sizeMultiplier))
        currentContext?.strokePath()

        //second part of top left corner
        currentContext?.beginPath()
        currentContext?.move(to: CGPoint(x: 0, y: self.bounds.size.height*sizeMultiplier))
        currentContext?.addLine(to: CGPoint(x: 0, y: 0))
        currentContext?.strokePath()
    }


    // Only override draw() if you perform custom drawing.
    // An empty implementation adversely affects performance during animation.
    override func draw(_ rect: CGRect) {
        // Drawing code
        super.draw(rect)
        self.drawCorners()
    }


}

EDITED

使用代码示例

import UIKit

class ViewController: UIViewController {

    var cornerViewCode : CornerView?
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        self.cornerViewCode = CornerView(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
        self.view.addSubview(self.cornerViewCode!)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

这就是它的样子

希望这可以帮助