倒圆图不显示在地图上

Question

我正在尝试在地图上创建一个倒置的MKCircle叠加层，但不会显示。

这里是我倒圆的课程代码：

import Foundation
import MapKit

class MKInvertedCircle : NSObject, MKOverlay {

    var coordinate: CLLocationCoordinate2D

    var boundingMapRect: MKMapRect {
        return MKMapRect.world
    }

    init(center coord: CLLocationCoordinate2D) {
        self.coordinate = coord
    }
}

这里是我的倒圆角渲染器类代码：

import Foundation
import UIKit
import MapKit

class MKInvertedCircleOverlayRenderer: MKOverlayRenderer {

var fillColor: UIColor = UIColor.red
var strokeColor: UIColor = UIColor.blue
var lineWidth: CGFloat = 3
var circle: MKCircle

init(circle: MKCircle) {
    self.circle = circle
    super.init(overlay: circle)
}

override func draw(_ mapRect: MKMapRect, zoomScale: MKZoomScale, in context: CGContext) {
    let path = UIBezierPath(rect: rect(for: MKMapRect.world))

    let excludePath: UIBezierPath = UIBezierPath(roundedRect: CGRect(x: circle.coordinate.latitude, y: circle.coordinate.longitude,
                                                                     width: circle.boundingMapRect.size.width,
                                                                     height: circle.boundingMapRect.size.height),
                                                 cornerRadius: CGFloat(circle.boundingMapRect.size.width))

    context.setFillColor(fillColor.cgColor)

    path.append(excludePath)
    context.addPath(path.cgPath)
    context.fillPath(using: .evenOdd)

    context.addPath(excludePath.cgPath)
    context.setLineWidth(9 / zoomScale)
    context.setStrokeColor(strokeColor.cgColor)
    context.strokePath()

    //line showing circle radius
    let lineBeginPoint = CGPoint(x: excludePath.bounds.midX, y: excludePath.bounds.midY)
    let lineEndPoint = CGPoint(x: excludePath.bounds.maxX, y: excludePath.bounds.midY)
    let linePath: UIBezierPath = UIBezierPath()
    linePath.move(to: lineBeginPoint)
    linePath.addLine(to: lineEndPoint)

    context.addPath(linePath.cgPath)
    context.setLineWidth(6/zoomScale)
    context.setStrokeColor(UIColor.black.cgColor)
    context.setLineDash(phase: 1, lengths: [20 / zoomScale, 10 / zoomScale])
    context.strokePath()

    // circle at the end of the line above
    let circleSize: CGFloat = 30/zoomScale
    let circleRect = CGRect(origin: CGPoint(x: lineEndPoint.x - (circleSize/2), y: lineEndPoint.y - (circleSize/2)),
                            size: CGSize(width: circleSize, height: circleSize))

    let circlePath: UIBezierPath =
        UIBezierPath(roundedRect: circleRect, cornerRadius: circleSize)

    context.addPath(circlePath.cgPath)
    context.setFillColor(UIColor.black.cgColor)
    context.fillPath()
}
}

编码新手，如果有人知道如何将其显示在地图上，将不胜感激！我从thread

复制了倒圆的代码