ios - Mapbox iOS 集群有效，但圆形样式层和数字层未出现/反射(reflect)集群的标记密度

Question

我正在使用 Mapbox 创建一个 iOS 应用程序。应用程序向我的 API 发出请求，以 JSON 格式返回 map 边界框内发生的许多事件。

我以前没有使用聚类，所以一些 map 注释只是覆盖了其他的。我正在使用 this Mapbox tutorial它从 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，一个圆圈层作为 MGLCircleStyleLayer，数字层作为 MGLSymbolStyleLayer。标记图层在地理上显示每个单独的事件，圆圈图层和数字图层一起表示每个集群的标记计数。

最终产品应该类似于 Mapbox 示例:

This is the GeoJSON file that the example uses在世界地图上显示集群海港。

以下是该示例用于将所述 GeoJSON 转换为相关源和图层以填充 map 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 正在接受它并根据其数据创建一个 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)
        }
    }

我知道此 GeoJSON 正在被转换为 MGLShapeCollectionFeature，因为如果不转换，应用程序会崩溃，而成功创建的 MGLShapeCollectionFeature 创建了正在创建图层的源来自/填充 map 。所以我从这个 MGLShapeCollectionFeature 创建了一个 MGLShapeSource:

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“源”创建图层并将它们添加到我的 map 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)

所以代码本质上是完全一样的，只是输入的 GeoJSON 不同。然而，当事件标记聚集时，圆圈层和数字层并没有出现。见下文:

我知道问题不在于 Mapbox 示例的源是从 URL 加载的，而我的实现的源是从 MGLShapeCollectionFeature 加载的，因为我已经尝试加载 Mapbox 示例的海港GeoJSON 作为 MGLShapeCollectionFeature 并且海港在集群时仍然显示圆圈/数字层。

Answer 1

所以，我觉得自己像个白痴。

问题出在 MGLShapeSource 中:

MGLShapeSource(identifier: "clusteredPoints", shape: shapes, options: [.clustered: true, .clusterRadius: 0.5])

无论出于何种原因，我一直在摆弄 clusterRadius，并将其设置为 0.5，我认为它以点为单位。请注意，该示例使用标记的宽度来确定簇半径。

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

我认为，因为一些标记在与另一个标记重叠时会消失，所以它们正在聚类，但未显示聚类层。它们没有聚集，我猜形状源只能知道它们何时与另一个重叠，并相应地消失。 仅仅因为它们消失并不意味着它们聚集在一起。