本例要实现的是如何利用Polygon Buffer自定义记录选中时的显示方式。
l 要点
首先通过IRgbColor接口和ISimpleFillSymbol接口设置Polygon Buffer的填充方式。然后在发生SelectionChanged事件时，设置选中记录被显示时的边界并将选中的Polygon通过ITopologicalOperator.ConstructUnion方法，联合成一个临时的Polygon Buffer，使用IActiveView.PartialRefresh方法刷新这个Polygon Buffer区域，最后在发生AfterItemDraw事件时将这个Polygon Buffer画在Map上。
主要用到IPolygon接口，IEnvelope接口，ISimpleFillSymbol接口，IActiveView接口，IEnumFeature接口，IGeometryCollection接口和ITopologicalOperator接口。
l 程序说明
函数InitEvents是初始化变量并设置Polygon Buffer的填充方式。
AfterItemDraw事件实现的是画出Polygon Buffer。
SelectionChanged事件实现的是生成Polygon Buffer并设置边界。
l 代码
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Private WithEvents ActiveViewEvents As Map
Private pMxDocument As IMxDocument
Private pBufferPolygon As IPolygon
Private pEnvelope As IEnvelope
Private pSimpleFillS As ISimpleFillSymbol
Public Sub InitEvents()
Dim pViewManager As IViewManager
Dim pRgbColor As IRgbColor
Set pMxDocument = Application.Document
Set pViewManager = pMxDocument.FocusMap
pViewManager.VerboseEvents = True
Set ActiveViewEvents = pMxDocument.FocusMap
\'Create a fill symbol
Set pSimpleFillS = New SimpleFillSymbol
Set pRgbColor = New RgbColor
pRgbColor.Red = 255
pSimpleFillS.Style = esriSFSForwardDiagonal
pSimpleFillS.Color = pRgbColor
End Sub
Private Sub ActiveViewEvents_AfterItemDraw(ByVal Index As Integer, ByVal Display As IDisplay, ByVal phase As esriDrawPhase)
\'Only draw in the geography phase
If Not phase = esriDPGeography Then Exit Sub
\'Draw the buffered polygon
If pBufferPolygon Is Nothing Then Exit Sub
With Display
.SetSymbol pSimpleFillS
.DrawPolygon pBufferPolygon
End With
End Sub
Private Sub ActiveViewEvents_SelectionChanged()
Dim pActiveView As IActiveView
Dim pEnumFeature As IEnumFeature
Dim pFeature As IFeature
Dim pSelectionPolygon As IPolygon
Dim pTopologicalOperator As ITopologicalOperator
Dim pGeometryCollection As IGeometryCollection
Set pActiveView = pMxDocument.FocusMap
Set pGeometryCollection = New GeometryBag
\'Flag last buffered region for invalidation
If Not pEnvelope Is Nothing Then
pActiveView.PartialRefresh esriViewGeography, Nothing, pEnvelope
End If
If pMxDocument.FocusMap.SelectionCount = 0 Then
\'Nothing selected; don\'t draw anything; bail
Set pBufferPolygon = Nothing
Exit Sub
End If
\'Buffer each selected feature
Set pEnumFeature = pMxDocument.FocusMap.FeatureSelection
pEnumFeature.Reset
Set pFeature = pEnumFeature.Next
Do While Not pFeature Is Nothing
Set pTopologicalOperator = pFeature.Shape
Set pSelectionPolygon = pTopologicalOperator.Buffer(0.1)
pGeometryCollection.AddGeometry pSelectionPolygon
\'Get next feature
Set pFeature = pEnumFeature.Next
Loop
\'Union all the buffers into one polygon
Set pBufferPolygon = New Polygon
Set pTopologicalOperator = pBufferPolygon \'QI
pTopologicalOperator.ConstructUnion pGeometryCollection
Set pEnvelope = pBufferPolygon.Envelope
\'Flag new buffered region for invalidation
pActiveView.PartialRefresh esriViewGeography, Nothing, pBufferPolygon.Envelope
End Sub
Private Sub UIButtonControl1_Click()
InitEvents
End Sub
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