如何实现在ArcMap上进行属性查询(Identify)

 

本例要演示的是如何查询Feature的属性信息。实现后的结果为选择了UI Tool Control后，在要查询的Feature上单击鼠标，查询的结果将显示在弹出的窗体上。

l   要点

首先需要得到要查询的Feature对象。使用IIdentify接口的Identify方法可以对给定的位置进行查询，得到结果为IIdentifyObj对象的数组。然后通过为IIdentifyObj对象设置IFeatureIdentifyObj查询接口，即可进一步得到Feature对象。因为IFeatureIdentifyObj接口的Feature属性具有只写（write only）属性，故又用到另一个接口IRowIdentifyObj。

得到Feature对象后即可操作其Fields属性和Value属性，得到其属性字段名和值。

l   程序说明

在窗体上使用了MSFlexGrid Control 6.0来显示查询结果。所以本例也演示了MSFlexGrid控件的使用方法。

窗体名：        frmResult

MSFlexGrid控件名：  flxAttr

标签控件名：    lblLocation （标签用来显示查询位置的地理坐标）

l   代码

Private Sub UIT_Identify_MouseDown(ByVal button As Long, ByVal shift As Long, _ ByVal x As Long, ByVal y As Long)

    Dim pMxApplication      As IMxApplication

    Dim pMxDocument         As IMxDocument

    Dim pMap                As IMap

    Dim pPoint              As IPoint

    Dim pIDArray            As IArray

    Dim pIdentify           As IIdentify

    Dim pFeatureIdentifyObj As IFeatureIdentifyObj

    Dim pIdentifyObj        As IIdentifyObj

    Dim pRowIdentifyObj     As IRowIdentifyObject

    Dim pFeature            As IFeature

    Dim pFields             As IFields

    Dim pField              As IField

    Dim iFieldIndex         As Integer

    Dim iLayerIndex         As Integer

    Dim sShape              As String

On Error GoTo ErrorHandler

    Set pMxApplication = Application

    Set pMxDocument = Application.Document

    Set pMap = pMxDocument.FocusMap

    'Identify from TOP layer to BOTTOM, exit loop since one Feature identified

    For iLayerIndex = 0 To pMap.LayerCount - 1

        Set pIdentify = pMap.Layer(iLayerIndex)

        'Convert x and y to map units

        Set pPoint = pMxApplication.Display.DisplayTransformation.ToMapPoint(x, y)

        'Set label on the form, coordinates would have 6 digits behind decimal point

        frmResult.lblLocation = "Location:(" & Format(pPoint.x, "##0.000000") & "," _ & Format(pPoint.y, "##0.000000") & ")"       

        Set pIDArray = pIdentify.Identify(pPoint)

        'Get the FeatureIdentifyObject

        If Not pIDArray Is Nothing Then

            Set pFeatureIdentifyObj = pIDArray.Element(0)

            Set pIdentifyObj = pFeatureIdentifyObj

            pIdentifyObj.Flash pMxApplication.Display

            'Feature property of FeatureIdentifyObject has write only access

            Set pRowIdentifyObj = pFeatureIdentifyObj

            Set pFeature = pRowIdentifyObj.Row

            Set pFields = pFeature.Fields

            'Set the MSFlexGrid control on form te display identify result

            With frmResult.flxAttr

                .AllowUserResizing = flexResizeColumns

                .ColAlignment(1) = AlignmentSettings.flexAlignLeftCenter

                .ColWidth(0) = 1500

                .ColWidth(1) = 1800

                'Add header to MSFlexGrid control

                .Rows = pFields.FieldCount + 1

                .Cols = 2

                .FixedRows = 1

                .FixedCols = 0

                .TextMatrix(0, 0) = "Field"

                .TextMatrix(0, 1) = "Value"

                For iFieldIndex = 0 To pFields.FieldCount - 1

                    Set pField = pFields.Field(iFieldIndex)

                    'Set field "Field" of the MSFlex control

                    .TextMatrix(iFieldIndex + 1, 0) = pField.Name

                    'Set field "Value" of the MSFlex control

                    Select Case pField.Type

                    Case esriFieldTypeOID

                        .TextMatrix(iFieldIndex + 1, 1) = pFeature.OID

                    Case esriFieldTypeGeometry

                        'The function QueryShapeType return a String that

                        '  correspond with the esriGeoemtryType const

                        sShape = QueryShapeType(pField.GeometryDef.GeometryType) .TextMatrix(iFieldIndex + 1, 1) = sShape

                 Case Else

                        .TextMatrix(iFieldIndex + 1, 1) = pFeature.Value(iFieldIndex)

                    End Select

                Next iFieldIndex

            End With

            frmResult.Show modal

            Exit Sub

        End If

    Next iLayerIndex

    'If code goes here, no Feature was indentified, clear the MSFlex control's content

    '  and show a message

    frmResult.flxAttr.Clear

    MsgBox "No feature identified."

    Exit Sub

ErrorHandler:

    MsgBox Err.Description

End Sub

 

Public Function QueryShapeType(ByVal enuGeometryType As esriGeometryType) As String

    Dim sShapeType As String  

    Select Case enuGeometryType

        Case esriGeometryPolyline

            sShapeType = "Polyline"

        Case esriGeometryPolygon

            sShapeType = "Polygon"

        Case esriGeometryPoint

            sShapeType = "Point"

        Case esriGeometryMultipoint

            sShapeType = "Multipoint"

        Case esriGeometryNull

            sShapeType = "Unknown"

        Case esriGeometryLine

            sShapeType = "Line"

        Case esriGeometryCircularArc

            sShapeType = "CircularArc"

        Case esriGeometryEllipticArc

            sShapeType = "EllipticArc"

        Case esriGeometryBezier3Curve

            sShapeType = "BezierCurve"

        Case esriGeometryPath

            sShapeType = "Path"

        Case esriGeometryRing

            sShapeType = "Ring"

        Case esriGeometryEnvelope

            sShapeType = "Envelope"

        Case esriGeometryAny

            sShapeType = "Any valid geometry"

        Case esriGeometryBag

            sShapeType = "GeometryBag"

        Case esriGeometryMultiPatch

            sShapeType = "MultiPatch"

        Case esriGeometryTriangleStrip

            sShapeType = "TriangleStrip"

        Case esriGeometryTriangeFan

            sShapeType = "TriangleFan"

        Case esriGeometryRay

            sShapeType = "Ray"

        Case esriGeometrySphere

            sShapeType = "Sphere"

        Case Else

            sShapeType = "Unknown!"

    End Select

    QueryShapeType = sShapeType

End Function