Mapbox iOS群集可以工作，但是圆形样式层和数字层没有出现/未反映群集的标记密度

时间：2019-04-17 20:55:50

标签： ios swift mapbox mapbox-gl mapbox-ios

我正在使用Mapbox创建iOS应用程序。该应用程序获取对我的API的请求，该请求以JSON格式返回地图边界框内发生的许多事件。

我以前没有使用聚类，所以一些地图注释只是覆盖了其他注释。我正在使用this Mapbox tutorial，它会从GeoJSON文件中创建一个MGLShapeCollectionFeature，然后从形状收集功能中创建一个MGLShapeSource，然后将标记层创建为一个MGLSymbolStyleLayer，一个圆圈层作为MGLCircleStyleLayer，数字层作为MGLSymbolStyleLayer。标记层在地理上显示每个事件，圆圈层和数字层合在一起表示每个聚类的标记数。

最终产品应类似于Mapbox示例：

enter image description here

This is the GeoJSON file that the example uses，以在世界地图上显示群集海港。

以下是示例中用于将所述GeoJSON转换为相关源和图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正在接受它，并根据其数据创建了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会被转换为MGLShapeCollectionFeature，因为如果不这样做，该应用程序将崩溃，并且成功创建的MGLShapeCollectionFeature创建了一个从地图上创建图层或填充地图的源。因此，我根据此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“源”创建图层，并将其添加到地图的样式中。

// 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)

因此代码本质上是完全相同的，只是输入的GeoJSON是不同的。但是，当事件标记聚集时，圆圈层和数字层不会出现。见下文：

enter image description here

我知道问题不在于从MGLShapeCollectionFeature加载我的实现源时，是从URL加载了Mapbox示例的源，因为我尝试将Mapbox示例的海港GeoJSON加载为MGLShapeCollectionFeature，并且群集时，海港仍显示圆圈/数字层。

1 个答案:

答案 0 :(得分：5)

所以，我觉得自己是个白痴。

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，我一直在弄乱clusterRadius，并将其设置为0.5，我以磅为单位。请注意，该示例使用标记的宽度确定聚类半径。

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

尽管如此，因为每当某些标记与另一个标记重叠时它们都会消失，因此它们正在聚类，但未显示聚类层。它们不是聚类的，我想形状源只能知道它们何时与另一个重叠，并且会相应消失。 仅仅因为它们消失并不意味着它们聚集在一起。

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