绘制带有边框 Mapbox 的多段线，iOS

Question

我正在使用 Mapbox iOS SDK 并尝试在没有 geojson 的情况下绘制折线。我试图用这种方法获取路线：

func calculateRoute() {

    ...

    let options = NavigationRouteOptions(waypoints: [origin, destination], profileIdentifier: .automobileAvoidingTraffic)
    Directions.shared.calculate(options) { (waypoints, routes, error) in 
        guard let route = routes?.first else { return }
        self.showPreview(route: route)
    }
}

然后我试着画了一条路线。

func showPreview(route: Route) {

    guard let steps = route.legs.first?.steps else { return }
    var points = [CLLocationCoordinate2D]()
    for step in steps {
        points.append(step.maneuverLocation)
    }
    let line = MGLPolyline(coordinates: &points, count: UInt(points.count))
    mapView?.addAnnotation(line)
}

它在地图视图上绘制折线。我可以使用两个委托方法 (MGLMapViewDelegate) 更改多段线的颜色和宽度：

func mapView(_ mapView: MGLMapView, lineWidthForPolylineAnnotation annotation: MGLPolyline) -> CGFloat {
    return 10
}

func mapView(_ mapView: MGLMapView, strokeColorForShapeAnnotation annotation: MGLShape) -> UIColor {
    return .blue
}

但我找不到在多段线周围设置边框宽度和边框颜色的方法。有什么办法吗？

Answer 1

看起来我有一个与您类似的用例（即不使用 geojson），结果是这样的。通过将您的路线与 MGLLineStyleLayer 相关联，您可以控制线路的视觉参数。

func showPreview(route: Route) {
    guard route.coordinateCount > 0 else { return }
    // Convert the route’s coordinates into a polyline
    var routeCoordinates = route.coordinates!
    let polyline = MGLPolylineFeature(coordinates: &routeCoordinates, count: route.coordinateCount)

    // If there's already a route line on the map, reset its shape to the new route
    if let source = mapView.style?.source(withIdentifier: "route-source") as? MGLShapeSource {
        source.shape = polyline
    } else {
        let source = MGLShapeSource(identifier: "route-source", features: [polyline], options: nil)

        // Customize the route line color and width
        let lineStyle = MGLLineStyleLayer(identifier: "route-style", source: source)
        lineStyle.lineColor = NSExpression(forConstantValue: UIColor.blue)
        lineStyle.lineWidth = NSExpression(forConstantValue: 3)

        // Add the source and style layer of the route line to the map
        mapView.style?.addSource(source)
        mapView.style?.addLayer(lineStyle)
    }
}

您想添加边框并控制其外观。如果您查看 Mapbox 网站上的这个示例：Line style Example 他们通过创建第二个 MGLLineStyleLayer 并将其插入到第一个下方来执行您想要的操作。他们称第二层为casingLayer。这是他们的代码，所以你可以看到它的形成方式与第一层相同。

let casingLayer = MGLLineStyleLayer(identifier: "polyline-case", source: source)
    // Add your formatting attributes here. See example on website.

然后他们将其插入第一行下方，因为它的宽度较宽，所以显示为边框。

style.insertLayer(casingLayer, below: lineStyle)

希望这对您有所帮助。

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