Swift：子类MKPolyline

Question

我正在开发一个请求多个路线的应用程序（MKDirectionsRequest）并在mapView中绘制路线，一切正常。

但是我遇到了一个问题：我想用不同的颜色绘制每条路线。

第一个想法很简单：使用标题/副标题来“标记”不同的MKPolyline，这样我就可以在委托函数中设置我想要的颜色：

mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer

但是我不喜欢这个解决方案，因为它“丑陋”，我将不得不解析一个字符串，我必须通过不同的params（流量..）

第二个简单的解决方案是继承MKPolyline，简单就是.. 由于MKPolyline没有指定的初始化程序，这是不可能的（是吗？）

[编辑]：我想创建一个MKPolyline的子类来复制“on it”已经创建的MKDirectionsRequest.routes返回的MKPolyline但我无法弄清楚如何覆盖只读参数（Apple说我们应该在子类中重写它们并添加setter，但是我在setter中有一个无限循环，女巫是......正常）

如果使用objC，在运行时“注入”代码并添加我的参数很简单，但我使用的是swift。

任何人都可以帮忙，谢谢。

Answer 1

不需要自定义渲染器的简单方法：

import UIKit
import MapKit

class CustomPolyline : MKPolyline {
    var color: UIColor?
}

class ViewController: UIViewController, MKMapViewDelegate {

    @IBOutlet weak var mapView: MKMapView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // setup mapView
        mapView.delegate = self

        // set map view region
        let location : CLLocationCoordinate2D = CLLocationCoordinate2DMake(51.4987, 0.007);
        let viewRegion = MKCoordinateRegionMakeWithDistance(location, 400, 400)
        mapView.setRegion(viewRegion, animated:true )

        // add red line
        let coords1 = [CLLocationCoordinate2D(latitude: 51.499526, longitude: 0.004785),CLLocationCoordinate2D(latitude: 51.500007, longitude: 0.005493)]
        let polyline1 = CustomPolyline(coordinates: coords1, count: coords1.count)
        polyline1.color = UIColor.red
        mapView.add(polyline1)

        // add blue line
        let coords2 = [CLLocationCoordinate2D(latitude: 51.498103, longitude: 0.007574), CLLocationCoordinate2D(latitude: 51.498190, longitude: 0.009677)]
        let polyline2 = CustomPolyline(coordinates: coords2, count: coords2.count)
        polyline2.color = UIColor.blue
        mapView.add(polyline2)

    }

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

    func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
        if overlay is CustomPolyline {
            let polylineRenderer = MKPolylineRenderer(overlay: overlay)
            polylineRenderer.strokeColor = (overlay as! CustomPolyline).color
            polylineRenderer.lineWidth = 4
            return polylineRenderer
        }
        return MKOverlayRenderer()
    }

}

Answer 2

为什么要为自定义MKOverlay设置颜色，难道你不能简单地将所需的颜色设置为MKOverlayRenderer？那应该很简单。

您也可以轻松地继承MKPolyline。我不明白为什么你不能这样做。

如果您希望能够创建自定义MKOverlay并设置自定义属性，然后将其绘制到地图中，您还需要创建自己的渲染器。这似乎是一项重大工作。但是，这是一个如何做到这一点的例子。

import UIKit
import MapKit


public class CustomOverlay: MKPolyline {
    public var customColor: UIColor?
}


public class CustomRenderer: MKPolylineRenderer {

    override public func strokePath(_ path: CGPath, in context: CGContext) {

        guard let overlayColor = self.overlay as? CustomOverlay, let color = overlayColor.customColor else {
            super.strokePath(path, in: context)
            return
        }

        context.saveGState()
        context.setStrokeColor(color.cgColor)
        context.addPath(path)
        context.drawPath(using: .stroke)
        context.restoreGState()
    }
}


public extension CLLocationCoordinate2D {
    static let Salo = CLLocationCoordinate2DMake(60.3909, 23.1355)
    static let Turku = CLLocationCoordinate2DMake(60.454510, 22.264824)
    static let Helsinki = CLLocationCoordinate2DMake(60.170833, 24.9375)
}


public class ViewController: UIViewController, MKMapViewDelegate {

    private var mapView: MKMapView!

    override public func viewDidLoad() {
        super.viewDidLoad()
        createMapView()
        setupMapView()
    }

    private func createMapView() {
        mapView = MKMapView(frame: .zero)
        mapView.translatesAutoresizingMaskIntoConstraints = false
        mapView.delegate = self
        view.addSubview(mapView)
        [mapView.topAnchor.constraint(equalTo: view.topAnchor),
         mapView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
         mapView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
         mapView.trailingAnchor.constraint(equalTo: view.trailingAnchor)].forEach { $0.isActive = true }
    }

    private func setupMapView() {

        let coordinates: [CLLocationCoordinate2D] = [.Helsinki, .Turku]

        let customPolyLine = CustomOverlay(coordinates: coordinates, count: coordinates.count)
        customPolyLine.customColor = UIColor.red
        mapView.add(customPolyLine)

        let coordinateSpan = MKCoordinateSpan(latitudeDelta: 3, longitudeDelta: 3)
        let region = MKCoordinateRegion(center: .Salo, span: coordinateSpan)
        mapView.setRegion(region, animated: true)
    }

    // MARK: MKMapViewDelegate

    public func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {

        /* return a simple renderer */
//        let renderer =  MKPolylineRenderer(overlay:overlay)
//        renderer.lineWidth = 2
//        renderer.lineDashPattern = [1, 2, 1]
//        renderer.strokeColor = UIColor.red
//        return renderer

        /* a custom renderer */
        let customRenderer = CustomRenderer(overlay: overlay)
        customRenderer.lineWidth = 2
        customRenderer.strokeColor = UIColor.green // this color is not used, since we apply color from overlay inside strokePath(:inContext:) method for custom renderer

        customRenderer.lineDashPattern = [1, 2, 1]
        return customRenderer
    }
}