在将多边形或折线添加到MKMapView时，防止替换WMS叠加层

问题描述

我已经通过将MKTileOverlay&使用MKTileOverlayRenderer渲染它.它可以正常工作并正确显示自定义地图.

I have implemented Web Map Service in the MKMapView by subclassing the MKTileOverlay & rendering it using MKTileOverlayRenderer. It works fine and displays the custom map properly.

当我调用mapView.addOverlay(polyLine)之类的方法来添加Polyline或Polygon时. WMS叠加层被Apple Maps取代.

When I call method like mapView.addOverlay(polyLine) to add Polyline or Polygon. The WMS overlay gets replaced with the Apple Maps overly.

// Set up the overlay and adds it to MKMapView.
func setupTileRenderer() {
    let wmsURL = formTemplate?.wmsURL
    let overlay = WMSTileOverlay(urlTemplate: wmsURL)
    overlay.canReplaceMapContent = true
    mapView.addOverlay(overlay, level: .aboveLabels)
    tileRenderer = MKTileOverlayRenderer(tileOverlay: overlay)
    wmsTileOverlay = overlay
}

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    if overlay is MKPolyline {
        let render = MKPolylineRenderer(overlay: overlay)
        render.lineWidth = 2
        render.strokeColor = UIColor.red
        return render
    } else if overlay is MKPolygon {
        let render = MKPolygonRenderer(overlay: overlay)
        render.lineWidth = 2
        render.strokeColor = UIColor.red
        return render
    } else if overlay is WMSTileOverlay {
        return tileRenderer!
    }
    return MKOverlayRenderer(overlay: overlay)
}

如何防止这种情况?我不希望在添加折线或多边形时替换wmsTileOverlay.

How do I prevent this? I don't want wmsTileOverlay to get replaced while adding polyline or polygon.

推荐答案

我意识到，在绘制多边形之前，我正在删除以前的叠加层，因此当时我正在删除所有叠加层.只是检查叠加层是WMSTileOverlay，然后不删除它.

I realised that before drawing the polygon I was removing the previous overlays so at that time I was removing all the overlays. Just checking the overlay is WMSTileOverlay then not removing it.

/// Clears the overlays added by the user.
func clearOverlaysOnMapView() {
    for overlay in mapView.overlays {
        if !(overlay is WMSTileOverlay) {
            mapView.removeOverlay(overlay)
        }
    }
}

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