AttributeGroupProvider Class

This class groups items based on the attribute values.

Namespace: DevExpress.XtraMap

Assembly: DevExpress.XtraMap.v20.1.dll

NuGet Package: DevExpress.Win.Map

Declaration

C#

public class AttributeGroupProvider :
    MapClustererGroupProviderBase

VB.NET

Public Class AttributeGroupProvider
    Inherits MapClustererGroupProviderBase

Remarks

This class introduces the AttributeGroupProvider.AttributeName property allowing you to specify the name of an attribute used to group items.

Example

This example shows how to cluster vector map items. Note that you can only cluster map items that implement the IClusterable interface (for example, MapDot, MapCallout, MapCustomElement and MapPushpin).

Assign an object of a class that implements the IMapDataAdapter.Clusterer interface to the IMapDataAdapter.Clusterer property. Then optionally, configure the clusterer. For example, all predefined clusters allow you to group items before clustering and allow you to customize the appearance of cluster representatives.

To group the items based on an attribute, assign AttributeGroupProvider to the MapClustererBase.GroupProvider property. Set the AttributeGroupProvider.AttributeName property to the item attribute name that should be used for clustering. After that, only items with the equal attribute value can be grouped into the same cluster.

Design a class that implements the IClusterItemFactory interface to customize the appearance of the cluster representatives. Then, call the MapClustererBase.SetClusterItemFactory method with an object of the class to assign the required factory object to the clusterer.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-aggregate-vector-items-using-a-clusterer-t311973

Form1.cs

VectorItemsLayer VectorLayer { get { return (VectorItemsLayer)map.Layers["VectorLayer"]; } }
ListSourceDataAdapter DataAdapter { get { return (ListSourceDataAdapter)VectorLayer.Data; } }

private void Form1_Load(object sender, EventArgs e) {
    DataAdapter.DataSource = LoadData();
    DistanceBasedClusterer clusterer = new DistanceBasedClusterer {
        GroupProvider = new AttributeGroupProvider {
            AttributeName = "LocationName"
        }
    };
    clusterer.SetClusterItemFactory(new CustomClusterItemFactory());
    DataAdapter.Clusterer = clusterer;
}
class CustomClusterItemFactory : IClusterItemFactory {
    public MapItem CreateClusterItem(IList<MapItem> objects) {
        MapDot dot = new MapDot();
        dot.ClusteredItems = objects;
        dot.TitleOptions.Pattern = objects.Count.ToString();
        return dot;
    }
}

Form1.vb

Private ReadOnly Property VectorLayer() As VectorItemsLayer
    Get
        Return CType(map.Layers("VectorLayer"), VectorItemsLayer)
    End Get
End Property
Private ReadOnly Property DataAdapter() As ListSourceDataAdapter
    Get
        Return CType(VectorLayer.Data, ListSourceDataAdapter)
    End Get
End Property
Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
    DataAdapter.DataSource = LoadData()
    Dim clusterer As DistanceBasedClusterer = New DistanceBasedClusterer With {
        .GroupProvider = New AttributeGroupProvider With {.AttributeName = "LocationName"}
    }
    clusterer.SetClusterItemFactory(New CustomClusterItemFactory())
    DataAdapter.Clusterer = clusterer
End Sub
Friend Class CustomClusterItemFactory
    Implements IClusterItemFactory

    Private Function CreateClusterItem(objects As IList(Of MapItem)) As MapItem Implements IClusterItemFactory.CreateClusterItem
        Dim dot As New MapDot()
        dot.ClusteredItems = objects
        dot.TitleOptions.Pattern = objects.Count.ToString()
        Return dot
    End Function
End Class

Implements

IClustererGroupProvider

Inheritance

Object

MapClustererGroupProviderBase

AttributeGroupProvider