在VB+Mapx5.0中新建图层及属性的源代码

最新推荐文章于 2011-06-15 21:05:00 发布

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本示例演示如何利用MapX的新增字段方法及LayerInfo对象创建新表格文件，并为来自mapstats.mdb中Us_Cust表的每条记录添加一个点要素，同时将选定属性数据（如公司名称、订单金额、城市和州）与每个添加的点要素相关联。

代码：

Private Sub Command1_Click()
'this sample used the new AddField methods and the LayerInfo object to make a new tab
'file.   for each record in the Us_Cust table (found in mapstats.mdb) it adds a point
'feature to the new table.   for each feature added to the table, selected attribute
'data from Us_Cust is associated with that point (the company name, order ammount, city
'and state).
   Dim rs As DAO.Recordset
       Dim db As DAO.Database

       Dim flds As New MapXLib.Fields

       Dim lyrNew As MapXLib.Layer
       Dim ptNew As New MapXLib.Point
       Dim ftrNew As MapXLib.Feature
       Dim ff As MapXLib.FeatureFactory
       Dim li As New MapXLib.LayerInfo
       Dim rvs As New MapXLib.Rowvalues
       Dim ds As MapXLib.Dataset

       'make database connection and get a recordset
       Set db = DBEngine.OpenDatabase("C:/Program Files/MapInfo/MapX 5.0/data/mapstats.mdb")
       Set rs = db.OpenRecordset("US_Cust")

       'we'll use feature factory later

       Set ff = Map1.FeatureFactory

       'define the columnar structure of the new table we're going to create
       flds.AddStringField "Company", 50
       flds.AddStringField "City", 50
       flds.AddStringField "State", 2
       flds.AddNumericField "Order_Amt", 12, 2

       'define the LayerInfo object
       li.Type = miLayerInfoTypeNewTable
       li.AddParameter "FileSpec", App.Path & "/custtab.tab"
       li.AddParameter "Name", "mycustomers"
       li.AddParameter "Fields", flds


       'add the new layer to the top of the map
       Map1.Layers.Add li, 1

       'make a dataset from the new layer and get its Rowvalues collection
       Set lyrNew = Map1.Layers(1)
       Set ds = Map1.Datasets.Add(miDataSetLayer, lyrNew)
       Set rvs = ds.Rowvalues(0)

       'for each records in the Us_Cust table we'll make a point feature and add it
       'to the newly created layer.   Using the Rowvalues object from that layer's
       'dataset we'll supply attribute data for each point feature added

       rs.MoveFirst
      Do While Not rs.EOF
            rvs.Item("Company").value = rs.Fields("Company")
            rvs.Item("City").value = rs.Fields("City")
            rvs.Item("State").value = rs.Fields("State")
            rvs.Item("Order_Amt").value = rs.Fields("Order_Amt")

            ptNew.Set rs.Fields("X"), rs.Fields("Y")
            Set ftrNew = ff.CreateSymbol(ptNew)
            Set ftrNew = lyrNew.AddFeature(ftrNew, rvs)

            rs.MoveNext

       Loop

      'close database connection
       Set rs = Nothing
      Set db = Nothing
End Sub