vba - 监听运行时创建的控件的事件

Question

我创建了一个类，当给定一个用户窗体作为参数时，应该在该用户窗体上放置一个控件并监听其事件。

简化的类是这样的:

eventsTestItem 类

Private WithEvents formControl As MSForms.Image
Private parentUF As MSForms.UserForm

Private Sub formControl_MouseDown(ByVal Button As Integer, ByVal Shift As Integer, ByVal X As Single, ByVal Y As Single)
MsgBox "clicked"
End Sub

Public Property Let Visible(ByVal makeVisible As Boolean)
    '(make) and show if true, otherwise delete
    If makeVisible Then
        ImageBase.Visible = True
    Else
        ParentForm.Controls.Remove ImageBase.Name
    End If
End Property

Public Property Set ItemParentUF(ByVal value As MSForms.UserForm)
    Set parentUF = value
End Property

Private Property Get ParentForm() As MSForms.UserForm
    If parentUF Is Nothing Then
        Err.Description = "Grid Item Requires parent Form to be set"
        Err.Raise 5                              'no parent uf set yet
    Else
        Set ParentForm = parentUF
    End If
End Property

Public Property Get ImageBase() As MSForms.Image
    If formControl Is Nothing Then
        Set formControl = ParentForm.Controls.Add("Forms.Image.1", Name:="TestImage", Visible:=False)
    End If
    Set ImageBase = formControl
End Property

Public Property Set ImageBase(value As MSForms.Image)
    Set formControl = value
End Property

我希望制作一个 Image 控件，我可以调整其事件。

为了测试，我使用以下代码创建了一个空用户表单:

Private Sub UserForm_Initialize()

    Dim testItem As New eventsTestItem  'create event listener class
    With testItem
        Set .ItemParentUF = Me   'tell it which userform to create a new control on
        .Visible = True     'Make and display the control
    End With
    Debug.Assert Me.Controls.Count = 1 'check if control added

End Sub

运行时没有错误(即控件已创建，它在表单上也可见)。

但是事件监听器没有按预期工作，当我单击图像时应该引发该事件。我在这里缺少什么？

Answer 1

一旦 UserForm_Initialize 返回，您的 testItem 实例就会被释放。

要使其正常工作，您必须将实例存储在过程范围之外。例如，您可以将其声明为Static以保持实例处于事件状态:

Private Sub UserForm_Click()
    Static testItem As Class1

    Set testItem = New Class1  'create event listener class
    With testItem
        Set .ItemParentUF = Me   'tell it which userform to create a new control on
        .Visible = True     'Make and display the control
    End With
    Debug.Assert Me.Controls.Count = 1 'check if control added

End Sub