如何在MapX下读取属性值
有三种方法:
1. 由Layer对象的KeyField属性来设立要读取属性值的字段名。
接着,由Feature对象的keyValue读取此行的属性值。
2. 将图层加入到Datasets, 由Dataset对象的Value(x,y)属性,通过设置行号,列号来获得属性值。
3. 将图层加入到Datasets,之后由RowValues(ftr)获取整行的值。
Dim ds As MapXLib.Dataset, lyr As MapXLib.layer
Dim ftrs As Features
Dim ftr As Feature
Dim rv As RowValue
Dim rvs As RowValues
Dim DsName As String ‘数据集名
Dim DsRows As Long, DsCols As Long
Dim i As Long, j As Long
Set ds = Formmain.Map1.Datasets.Item(DsName)
Set lyr = ds.layer
Set ftrs = lyr.AllFeatures
DsCols = ds.Fields.Count
DsCols = DsCols + 1
DsRows = ftrs.Count
Grid1.Rows = DsRows + 1
Grid1.Cols = DsCols
Grid1.Row = 0
For i = 0 To DsCols - 1
Grid1.Col = i
Grid1.Text = ds.Fields.Item(i + 1).Name
Next i
Grid1.Col = DsCols - 1
Grid1.Text = "Fkey"
lyr.BeginAccess miAccessRead
i = 1
For Each ftr In ftrs
Set rvs = ds.RowValues(ftr)
j = 0
For Each rv In rvs
If Not IsNull(rv.Value) Then Grid1.TextArray(i * DsCols + j) = Trim(rv.Value)
j = j + 1
Next
Grid1.TextArray(i * DsCols + j) = ftr.FeatureKey
i = i + 1
Next
lyr.EndAccess miAccessEnd
Set ftr = Nothing
Set ftrs = Nothing
Set ds = Nothing
Set rv = Nothing
Set rvs = Nothing
Set lyr = Nothing
注意:BeginAccess,以及EndAccess可以明显的提高属性读取的速度。