一个简单的空间分析例子：vb实现在地图上画一个矩形或者
圆后,计算出该区域内的要素的数目。
创建临时图层
在临时图层上用程序或者让用户手动的创建一个矩形或者圆形
然后使用空间过滤器,spatialfilter
指定一下它的参数,进行查找就行了。
具体的使用在帮助文档里有。
在地图上画矩形或者圆形可以通过INewCircleFeedback接口实现，画矩形同理，只需转换使用的接口就可以了，以下以画圆形为例（该代码是在ArcMap的VBA环境下，建立用户控件使用的）：
Private m_pDoc As IMxDocument
Private m_pAV As IActiveView
Private m_pScrD As IScreenDisplay
Private m_pNewCircFeedback As INewCircleFeedback
Private Function UIToolControl1_Enabled() As Boolean
'Set the ToolControl to enabled (disabled by default if any code is present in this event)
UIToolControl1_Enabled = True
'Check that we have a reference to the ActiveView and ScreenDisplay
If m_pScrD Is Nothing Then
Set m_pDoc = Application.Document
Set m_pAV = m_pDoc.ActiveView
Set m_pScrD = m_pAV.ScreenDisplay
End If
End Function
Private Sub UIToolControl1_MouseDown(ByVal button As Long, ByVal shift As Long, ByVal x As Long, ByVal y As Long)
Dim pPnt As IPoint
' Get the current mouse location in Map Units
Set pPnt = m_pScrD.DisplayTransformation.ToMapPoint(x, y)
' Check that user is not using an existing feedback
If m_pNewCircFeedback Is Nothing Then
' Create a NewCircleFeedback object
Set m_pNewCircFeedback = New NewCircleFeedback
'Set the Feedback's Display and StartPoint
Set m_pNewCircFeedback.Display = m_pScrD
m_pNewCircFeedback.Start pPnt
End If
End Sub
Private Sub UIToolControl1_MouseMove(ByVal button As Long, ByVal shift As Long, ByVal x As Long, ByVal y As Long)
' Check if the user is currently using the feedback
If Not m_pNewCircFeedback Is Nothing Then
Dim pPnt As IPoint
'Move the Feedback to the current mouse location
Set pPnt = m_pScrD.DisplayTransformation.ToMapPoint(x, y)
m_pNewCircFeedback.MoveTo pPnt
End If
End Sub
Private Sub UIToolControl1_MouseUp(ByVal button As Long, ByVal shift As Long, ByVal x As Long, ByVal y As Long)
Dim pCircArc As IGeometry
' Check if the user is currently using the feedback
If Not m_pNewCircFeedback Is Nothing Then
'Get the geometry (ICircularArc) returned from the feedback
Set pCircArc = m_pNewCircFeedback.Stop
' If it is valid then create a CircleElement on the ActiveView using the 'AddCreateElement' procedure
If Not pCircArc Is Nothing Then
AddCreateElement pCircArc, m_pAV
m_pAV.Refresh
End If
' Set the feedback to nothing for the next use
Set m_pNewCircFeedback = Nothing
End If
End Sub
Private Sub AddCreateElement(pCircArc As ICircularArc, pAV As IActiveView)
' Takes an ICircularArc and IActiveView and creates a CircleElement in the ActiveView's BasicGraphicsLayer
Dim pElemFillShp As IFillShapeElement
Dim pElem As IElement
Dim pGraCont As IGraphicsContainer
Dim pSFSym As ISimpleFillSymbol
Dim pRGB As IRgbColor
Dim pSegColl As ISegmentCollection
' Create a new Polygon object and access the ISegmentCollection interface to add a segment
Set pSegColl = New Polygon
pSegColl.AddSegment pCircArc
' Create a new circleelement and use the IElement interface to set the its Geometry
Set pElem = New CircleElement
pElem.Geometry = pSegColl
' QI for the IFillShapeElement interface so that the Symbol property can be set
Set pElemFillShp = pElem
' Create a new RGBColor
Set pRGB = New RgbColor
With pRGB
.Red = 198
.Green = 255
.Blue = 214
End With
' Create a new SimpleFillSymbol and set its Color and Style
Set pSFSym = New SimpleFillSymbol
pSFSym.Color = pRGB
pSFSym.Style = esriSFSSolid
pElemFillShp.Symbol = pSFSym
' QI for the IGraphicsContainer interface from the IActiveView, allows access to the BasicGraphicsLayer
Set pGraCont = pAV
'Add the element at Z order zero
pGraCont.AddElement pElemFillShp, 0
End Sub
至于搜索，只需在取得pCircArc后利用ISpatialFilter即可实现，代码如下：
Dim pFilter As IspatialFilter
Set pFilter = New SpatialFilter
With pFilter
Set .Geometry = pCircArc
.GeometryField = "SHAPE"
.SpatialRel = esriSpatialRelIntersects
End With
dim featureCount as Integer
featurecount=pFeatureClass.FeatureCount pFilter
featurecount即为要搜索的pfeatureclass中的实体个数
