为实例化的表单对象捕获 onClose 事件

Posted 2023-05-07

【中文标题】为实例化的表单对象捕获 onClose 事件

【英文标题】：Trap onClose event for instantiated form object

【发布时间】：2016-07-16 06:58:57

【问题描述】：

如何为手动实例化的表单对象捕获 onClose 或 onUnload 事件？

我注意到如果（在我的控制器类中），我使用 WithEvents 关键字标注了一个 Access.Textbox 或 Access.CommandButton 对象，然后 Access VBA IDE 将自动在代码窗口上方的组合框中显示该对象及其可用事件。

但是，如果我使用 WithEvents 关键字标注了一个 Form 对象或自定义 Form 对象，则没有列出对象或可用事件。

Form_Popup_Credentials（表单代码）：

Public Event CustomUnLoad()

Private Sub Form_Unload(Cancel As Integer)
  RaiseEvent CustomUnLoad
End Sub

FormController 类：

Dim WithEvents Loginfrm As Form_Popup_Credentials
Dim WithEvents Loginbtn As Access.CommandButton

Public Sub GetCredentials()
  ' If the Popup Credential form is not instantiated,
  ' then bring it into existence
  If Loginfrm Is Nothing Then
    Set Loginfrm = New Form_Popup_Credentials
  End If

  ' Set up a reference to the "Login" button
  Set Loginbtn = Loginfrm.SignInButton

  ' Set up the Login Button Click() event
  Loginbtn.OnClick = "[Event Procedure]"

  ' Set up the Login Form's events
  Loginfrm.OnUnload = "[Event Procedure]"
  Loginfrm.OnClose = "[Event Procedure]"

  ' Show the form and give it focus
  Loginfrm.Visible = True
  Loginfrm.SetFocus
End Sub

' Fires Correctly
Private Sub Loginbtn_Click()
  MsgBox "Login Button was Clicked"

  ' If I uncomment this, then the CustomUnLoad() event fires
  ' DoCmd.Close acForm, Loginfrm.Name, acSavePrompt

  Set Loginbtn = Nothing
  Set Loginfrm = Nothing
End Sub

' Doesn't Fire
Private Sub Loginfrm_onClose()
  MsgBox "Login Form onClose() fired"
  Set Loginfrm = Nothing
  Set Loginbtn = Nothing
End Sub

' Doesn't Fire
Private Sub Loginfrm_Close()
  MsgBox "Login Form Close() fired"
  Set Loginfrm = Nothing
  Set Loginbtn = Nothing
End Sub

' Doesn't Fire
Private Sub Loginfrm_onUnload()
  MsgBox "Login Form onUnload() fired"
  Set Loginfrm = Nothing
  Set Loginbtn = Nothing
End Sub

' Doesn't Fire
Private Sub Loginfrm_Unload()
  MsgBox "Login Form Unload() fired"
  Set Loginfrm = Nothing
  Set Loginbtn = Nothing
End Sub

' This fires if the user clicks the X button to close the form,
' but not if the controller unloads the Loginfrm object
Private Sub Loginfrm_CustomUnLoad()
  MsgBox "Login Form CustomUnLoad() fired"
  Set Loginfrm = Nothing
  Set Loginbtn = Nothing
End Sub

【问题讨论】：

刚试过，Dim WithEvents Loginfrm As Form 为我工作，我看到了事件的控制和列表。但是Dim WithEvents Loginfrm As Form_Popup_Credentials 甚至无法编译。如果您需要表单实例中的自定义事件，我建议您查看接口类并以Implements IMyFormEvents

之类的形式使用它

【参考方案1】：

您必须将您的类级别表单变量声明为Form（或更明确的Access.Form）才能获得Access 表单的标准事件：

Dim WithEvents Loginfrm As Access.Form

顺便说一句，根据 Access 版本，确保将控制器类中的引用设置为 Nothing on Class_Terminate 至关重要。

【讨论】：

我明白我做错了什么。我试图将对象与声明匹配： Dim WithEvents Loginfrm As Access.Form Set Loginfrm = New Access.Form 但只需更改声明即可。谢谢