ms-access - Access VBA : Iterating controls on a form, 显示仅某些控件类型具有的属性

Question

我正在尝试迭代表单上的控件以显示那些支持 ControlSource 的控件的 ControlSource 属性。

我发现识别具有 ControlSource 属性的控件相对容易。问题在于 Access 这些控件的属性。通用 Control 对象没有 ControlSource 属性。如果我使用另一种语言，我只需将列表框控件转换为 ListBox 对象，例如，以 Access ControlSource 属性。但我的理解是，在 VBA 中没有类型继承，所以我不能将一种类型的对象转换为另一种类型。

那么如何 Access 支持该属性的控件的 ControlSource 属性呢？

这是我到目前为止的代码:

Private Sub IterateControlsOnForm()
Dim frm As Form, formName As String
' The only controls that have a ControlSource property are either
'   BoundObjectFrame controls or ListBox controls.
Dim ctrl As Control
Dim boundObjectFrame As boundObjectFrame, listBoxCtrl As listBox
Dim boundObjectFrameTypes() As String, listBoxTypes() As String
Dim ctrlType As String

    formName = "MAINFORM"

    ' Useful way of populating a string array - use Split function.
    '   Array function only works with Variants.
    boundObjectFrameTypes = _
        Split("CheckBox,ComboBox,CustomControl,GroupLevel", ",")
    listBoxTypes = Split("OptionButton,OptionGroup,TextBox,TextBox", ",")

    ' Assumes form is open.
    Set frm = Forms(formName)
    For Each ctrl In frm.Controls
        ' Ignore controls that do not have a ControlSource property.
        ctrlType = TypeName(ctrl)
        If IsStringInArray(ctrlType, boundObjectFrameTypes) Then
            ' **** FOLLOWING LINE FAILS ****
            Set boundObjectFrame = ctrl
            Debug.Print boundObjectFrame.Name & "(" & ctrlType & ") " & _
                "ControlSource Property: " & boundObjectFrame.ControlSource
        ElseIf IsStringInArray(ctrlType, listBoxTypes) Then
            ' **** FOLLOWING LINE FAILS ****
            Set listBoxCtrl = frm.Controls(ctrl.Name)
            Debug.Print listBoxCtrl.Name & "(" & ctrlType & ") " & _
                "ControlSource Property: " & listBoxCtrl.ControlSource
        End If
    Next ctrl
End Sub

我尝试了两种方法将通用 Control 对象转换为具有 ControlSource 属性的更具体的控件。请参阅两条评论“** FOLLOWING LINE FAILS **”。

Answer 1

使用对象怎么样？

Private Sub IterateControlsOnForm()
Dim frm As Form, formName As String
' The only controls that have a ControlSource property are either
'   BoundObjectFrame controls or ListBox controls.
Dim ctrl As Control
Dim boundObjectFrame As Object, listBoxCtrl As Object
Dim boundObjectFrameTypes As String, listBoxTypes As String
Dim ctrlType As String

    formName = "MAINFORM"

    ' Useful way of populating a string array - use Split function.
    '   Array function only works with Variants.
    boundObjectFrameTypes = _
        ",CheckBox,ComboBox,CustomControl,GroupLevel"
    listBoxTypes = ",OptionButton,OptionGroup,TextBox,TextBox"

    ' Assumes form is open.
    Set frm = Forms(formName)
    For Each ctrl In frm.Controls
        ' Ignore controls that do not have a ControlSource property.
        ctrlType = TypeName(ctrl)
        If InStr(boundObjectFrameTypes, "," & ctrlType) Then
            Set boundObjectFrame = ctrl
            Debug.Print boundObjectFrame.Name & "(" & ctrlType & ") " & _
                "ControlSource Property: " & boundObjectFrame.ControlSource
        ElseIf InStr(listBoxTypes, "," & ctrlType) Then
            Set listBoxCtrl = frm.Controls(ctrl.Name)
            Debug.Print listBoxCtrl.Name & "(" & ctrlType & ") " & _
                "ControlSource Property: " & listBoxCtrl.ControlSource
        End If
    Next ctrl
End Sub

使用 VBA，您还可以使用 On Error Resume Next，但我同意通常最好避免错误。

formName = "MAINFORM"

Set frm = Forms(formName)
For Each ctrl In frm.Controls
On Error Resume Next
    Debug.Print ctrl.Name _
        & " ControlSource Property: " & ctrl.ControlSource
    If Err.Number = 438 Then
        Err.Clear
    End If
Next