增加经线和纬线

本示例内容可以参考CaseStudy目录下的文件"地图.Table"的示例二十八。

本节的任务是在地图上增加经线和纬线：

AfterLoad事件代码：

Dim map As GeoMap = e.Form.Controls("Map1").GeoMap
Dim layer As New VectorLayer()
layer.Style.Stroke.Color = Color.DarkGray
layer.LabelVisibility = LabelVisibility.AutoHide
map.Layers.Add(layer)
For Each kr As VectorRecord In map.CreateRecordsFromKML(ProjectPath & "WorldMap.kml")
    layer.Items.Add(kr.VectorItem)
    If TypeOf kr.VectorItem Is VectorPlacemark Then
        Dim mark As VectorPlacemark = kr.VectorItem
        '设置标记的属性:
        mark.Marker.Caption = kr.Data("name")
        mark.Marker.LabelPosition = LabelPosition.Center
        mark.LabelStyle.ForeColor = Color.Green
        mark.Lod = New LOD(0, 0, 2, 20)
    ElseIf TypeOf kr.VectorItem Is VectorPolygon Then
        Dim polygon As VectorPolygon = kr.VectorItem
        '设置多边形属性:
        If kr.Data("style-fillcolor") IsNot Nothing Then '其他国家从KML取得颜色设置，如果有的话
            polygon.Style.BackColor = map.GetKmlStyleColor(kr.Data("style-fillcolor"))
        End If
    End If
Next
'增加一个图层用于绘制经线和维线
layer = New VectorLayer()
layer.LabelVisibility = LabelVisibility.Visible
layer.Track = False
map.Layers.Add(layer)
layer.LabelStyle.ForeColor = Color.DarkGray
layer.Style.Stroke.Color = Color.DarkGray
layer.Style.Stroke.Style = GeoDashStyle.Dash
For lon As Integer = -180 To 180 Step 30 '间隔30度绘制一条经线
    layer.Items.Add(map.CreateLine({New GeoPoint(lon, -90), New GeoPoint(lon, 90)}))
    Dim lbl As String = Math.Abs(lon).ToString() & "°"
    If lon > 0 Then
        lbl = lbl & "E"
    ElseIf lon < 0 Then
        lbl = lbl & "W"
    End If
    Dim pm As New VectorPlacemark()
    pm.Geometry = New GeoPoint(lon, 0)
    pm.Marker = New Marker()
    pm.Marker.Caption = lbl
    pm.Marker.LabelPosition = LabelPosition.Top
    layer.Items.Add(pm)
Next
For lat As Integer = -80 To 80 Step 20 '间隔20度绘制一条纬线
    layer.Items.Add(map.CreateLine({New GeoPoint( - 180, lat), New GeoPoint(180, lat)}))
    Dim lbl As String = Math.Abs(lat).ToString() & "°"
    If lat > 0 Then
        lbl = lbl & "N"
    ElseIf lat < 0 Then
        lbl = lbl & "S"
    End If
    Dim pm As New VectorPlacemark()
    pm.Geometry = New GeoPoint(0, lat)
    pm.Marker = New Marker()
    pm.Marker.Caption = lbl
    pm.Marker.LabelPosition = LabelPosition.Right
    layer.Items.Add(pm)
Next