MKPolyline与MapKit缩放有关的奇怪渲染 [英] MKPolyline strange rendering related with zooming in MapKit

问题描述

我有一个非常简单的View Controller来演示MKPolyline的这种奇怪的渲染行为.普通的api调用没什么特别的.

I have very simple View Controller to demonstrate this strange rendering behavior of MKPolyline. Nothing special just normal api calls.

import UIKit
import MapKit

class ViewController: UIViewController, MKMapViewDelegate {

    @IBOutlet weak var map: MKMapView!

    override func viewDidLoad() {
        super.viewDidLoad()
        map.delegate = self
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        let p1 = CLLocationCoordinate2D(latitude: 51, longitude: 13)
        var coords = [
            p1,
            CLLocationCoordinate2D(latitude: 51.1, longitude: 13),
            CLLocationCoordinate2D(latitude: 51.2, longitude: 13),
            CLLocationCoordinate2D(latitude: 51.3, longitude: 13)
        ]

        let polyline = MKPolyline(coordinates: &coords, count: coords.count)
        map.addOverlays([polyline], level: .aboveRoads)
        let cam = MKMapCamera(lookingAtCenter: p1, fromDistance: 1000, pitch: 45, heading: 0)
        map.setCamera(cam, animated: true)
    }

    func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
        let r = MKPolylineRenderer(overlay: overlay)
        r.strokeColor = UIColor.blue
        return r
    }
}

折线的渲染非常奇怪.在缩放和平移期间，您会看到一些伪像.

The rendering of the polyline is very strange. During zooming and panning You can see some artifacts.

看看下面的图片:

初始屏幕

平移后

缩小并再次放大后

如何解决此问题?我试图实现自己的渲染器，但情况相同.就像overaly被缓存一样，它没有按时重绘.我正在使用iOS SDK 10 xCode 8上的iOS 10，iPhone 6，模拟器.

How to fix this? I was trying to implement my own renderer but its the same situation. Like overaly is cached and it's not redrawing on time. I'm working on iOS 10, iPhone 6, Simulator from iOS SDK 10 xCode 8.

推荐答案

Swift 3解决方案:

Swift 3 solution :

创建MKPolylineRenderer的子类

Create a subclass of MKPolylineRenderer

class CustomPolyline: MKPolylineRenderer {

    override func applyStrokeProperties(to context: CGContext, atZoomScale zoomScale: MKZoomScale) {
        super.applyStrokeProperties(to: context, atZoomScale: zoomScale)
        UIGraphicsPushContext(context)
        if let ctx = UIGraphicsGetCurrentContext() {
            ctx.setLineWidth(self.lineWidth)
        }
    }
}

然后在渲染器中使用它用于MapKit委托:

Then use it in your rendererFor MapKit delegate :

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
        let renderer = CustomPolyline(overlay: overlay)
        renderer.strokeColor = UIColor.red
        renderer.lineWidth = 100
        return renderer
}

您的折线在缩放后不会重新渲染，从而避免了伪像

Your polylines won't re-render after zooming thus avoiding the artifacts

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