Mapbox iOS群集可以工作，但是圆形样式图层和数字图层不会出现/反映群集的标记密度

Question

我正在使用Mapbox创建ios应用程序。应用程序获取对我的API发出请求，该请求返回以JSON格式在地图的边界框内进行的许多事件。

我以前没有使用群集，因此一些地图注释只是覆盖其他人。我正在使用this Mapbox tutorial从GeoJSON文件创建一个MGLShapeCollectionFeature，从形状集合特征创建一个MGLShapeSource，然后创建一个标记层作为MGLSymbolStyleLayer，一个圆层作为MGLCircleStyleLayer，一个数字层作为MGLSymbolStyleLayer。标记层在地理上显示每个单独的事件，圆圈层和数字层聚集在一起以表示每个群集的标记计数。

最终产品应该与Mapbox示例类似：

This is the GeoJSON file that the example uses在世界地图上显示聚类海港。

以下是该示例用于将所述GeoJSON转换为相关源和层以填充地图的相关代码：

let url = URL(fileURLWithPath: Bundle.main.path(forResource: "ports", ofType: "geojson")!)

let source = MGLShapeSource(identifier: "clusteredPorts",
    url: url,
    options: [.clustered: true, .clusterRadius: icon.size.width])
style.addSource(source)

// Use a template image so that we can tint it with the `iconColor` runtime styling property.
style.setImage(icon.withRenderingMode(.alwaysTemplate), forName: "icon")

// Show unclustered features as icons. The `cluster` attribute is built into clustering-enabled
// source features.
let ports = MGLSymbolStyleLayer(identifier: "ports", source: source)
ports.iconImageName = NSExpression(forConstantValue: "icon")
ports.iconColor = NSExpression(forConstantValue: UIColor.darkGray.withAlphaComponent(0.9))
ports.predicate = NSPredicate(format: "cluster != YES")
style.addLayer(ports)

// Color clustered features based on clustered point counts.
let stops = [
    20: UIColor.lightGray,
    50: UIColor.orange,
    100: UIColor.red,
    200: UIColor.purple
]

// Show clustered features as circles. The `point_count` attribute is built into
// clustering-enabled source features.
let circlesLayer = MGLCircleStyleLayer(identifier: "clusteredPorts", source: source)
circlesLayer.circleRadius = NSExpression(forConstantValue: NSNumber(value: Double(icon.size.width) / 2))
circlesLayer.circleOpacity = NSExpression(forConstantValue: 0.75)
circlesLayer.circleStrokeColor = NSExpression(forConstantValue: UIColor.white.withAlphaComponent(0.75))
circlesLayer.circleStrokeWidth = NSExpression(forConstantValue: 2)
circlesLayer.circleColor = NSExpression(format: "mgl_step:from:stops:(point_count, %@, %@)", UIColor.lightGray, stops)
circlesLayer.predicate = NSPredicate(format: "cluster == YES")
style.addLayer(circlesLayer)

// Label cluster circles with a layer of text indicating feature count. The value for
// `point_count` is an integer. In order to use that value for the
// `MGLSymbolStyleLayer.text` property, cast it as a string.
let numbersLayer = MGLSymbolStyleLayer(identifier: "clusteredPortsNumbers", source: source)
numbersLayer.textColor = NSExpression(forConstantValue: UIColor.white)
numbersLayer.textFontSize = NSExpression(forConstantValue: NSNumber(value: Double(icon.size.width) / 2))
numbersLayer.iconAllowsOverlap = NSExpression(forConstantValue: true)
numbersLayer.text = NSExpression(format: "CAST(point_count, 'NSString')")

numbersLayer.predicate = NSPredicate(format: "cluster == YES")
style.addLayer(numbersLayer)

This is the GeoJSON format that my events are being returned from my API as。这种格式应该是正确的，因为Mapbox接受它并从其数据创建MGLShapeCollectionFeature。

我的代码与Mapbox示例中的代码非常相似。我首先创建GeoJSON文件

//geoJson is my GeoJSON file as [String: Any]
var shapes: MGLShapeCollectionFeature!

    if let data = try? JSONSerialization.data(withJSONObject: geoJson, options: .prettyPrinted) {

        do {

            shapes = try MGLShape(data: data, encoding: String.Encoding.utf8.rawValue) as! MGLShapeCollectionFeature

        } catch {
            print(error.localizedDescription)
        }
    }

我知道这个GeoJSON正被转换为MGLShapeCollectionFeature，因为如果没有，应用程序会崩溃，并且MGLShapeCollectionFeature创建成功创建了一个源，正在从/填充地图创建图层。所以我从这个MGLShapeSource创建了一个MGLShapeCollectionFeature：

let marker = UIImage(named: "redPin")?.resize(targetSize: CGSize(width: 25, height: 25))
let source = MGLShapeSource(identifier: "clusteredPoints", shape: shapes, options: [.clustered: true, .clusterRadius: 0.5])
self.mapStyle!.addSource(source)


// Use a template image so that we can tint it with the `iconColor` runtime styling property.
self.mapStyle!.setImage(marker!, forName: "marker")

然后我从'source'创建图层并将它们添加到我的地图样式中。

// Show unclustered features as icons. The `cluster` attribute is built into clustering-enabled
// source features.
let events = MGLSymbolStyleLayer(identifier: "events", source: source)
events.iconImageName = NSExpression(forConstantValue: "marker")
events.iconColor = NSExpression(forConstantValue: UIColor.darkGray.withAlphaComponent(0.9))
events.predicate = NSPredicate(format: "cluster != YES")
self.mapStyle!.addLayer(events)

// Color clustered features based on clustered point counts.
let stops = [
    5: UIColor.lightGray,
    10: UIColor.orange,
    20: UIColor.red,
    30: UIColor.purple
]

// Show clustered features as circles. The `point_count` attribute is built into
// clustering-enabled source features.
let circlesLayer = MGLCircleStyleLayer(identifier: "clusteredEvents", source: source)

circlesLayer.circleRadius = NSExpression(forConstantValue: NSNumber(value: Double(self.mapStyle!.image(forName: "marker")!.size.width) / 2))
circlesLayer.circleOpacity = NSExpression(forConstantValue: 0.75)
circlesLayer.circleStrokeColor = NSExpression(forConstantValue: UIColor.white.withAlphaComponent(0.75))
circlesLayer.circleStrokeWidth = NSExpression(forConstantValue: 2)
circlesLayer.circleColor = NSExpression(format: "mgl_step:from:stops:(point_count, %@, %@)", UIColor.lightGray, stops)
circlesLayer.predicate = NSPredicate(format: "cluster == YES")
self.mapStyle!.addLayer(circlesLayer)


// Label cluster circles with a layer of text indicating feature count. The value for
// `point_count` is an integer. In order to use that value for the
// `MGLSymbolStyleLayer.text` property, cast it as a string.
let numbersLayer = MGLSymbolStyleLayer(identifier: "clusteredEventsNumbers", source: source)
numbersLayer.textColor = NSExpression(forConstantValue: UIColor.white)
numbersLayer.textFontSize = NSExpression(forConstantValue: NSNumber(value: Double(self.mapStyle!.image(forName: "marker")!.size.width) / 2))
numbersLayer.iconAllowsOverlap = NSExpression(forConstantValue: true)
numbersLayer.text = NSExpression(format: "CAST(point_count, 'NSString')")

numbersLayer.predicate = NSPredicate(format: "cluster == YES")
self.mapStyle!.addLayer(numbersLayer)

所以代码基本上完全相同，只是输入的GeoJSON是不同的。然而，当事件标记聚类时，圆层和数字层不会出现。见下文：

我知道问题不是Mapbox示例的源是从URL加载的，而我的实现源是从MGLShapeCollectionFeature加载的，因为我已经尝试将Mapbox示例的seaports GeoJSON加载为MGLShapeCollectionFeature而且seports仍然显示聚集时圈数/数字层。