Article: Q170370
Product(s): Microsoft Visual Basic for Windows
Version(s):
Operating System(s):
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, version 6.0
- Microsoft Visual Basic Professional Edition for Windows, version 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0
- Microsoft Visual Basic Professional Edition for Windows, version 5.0
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0
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SYMPTOMS
========
Visual Basic versions 5.0 and higher allow developers to create in-process
ActiveX servers with non-modal forms. However, when a user switches between a
non-modal form that is part of the main application and a non-modal form that is
part of an in-process ActiveX server, the Deactivate Event of the forms will not
fire.
RESOLUTION
==========
You can work around this limitation using any message hooking control or
AddressOf. See the REFERENCES section below for more information.
The message you need to hook is WM_ACTIVATE. When you receive WM_ACTIVATE you
should check the lower word of the wParam to see if it is equal to WA_INACTIVE.
If it is then your form is being deactivated and you can call your deactivation
code. The following code snippet shows how your message handler would work:
Private Const WM_ACTIVATE As Long = &H6
Private Const WA_INACTIVE As Integer = 0
Private Const WA_ACTIVE As Integer = 1
Private Const WA_CLICKACTIVE As Integer = 2
Function WindowProc(ByVal hw As Long, ByVal uMsg As _
Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Select Case Msg
Case WM_ACTIVATE
Dim fActive As Integer
fActive = &HFFFF& And wparam
Select Case fActive
Case WA_INACTIVE
' Call deactivation code here
Case WA_ACTIVE
' Call activation code here
Case WA_CLICKACTIVE
' Call activation code here
Case Else
End Select
Case Else
End Select
End Function
NOTE: If you have third-party controls on your form, they may be subclassing the
form as well. If you try to remove your subclass in this scenario, you could
crash. In these circumstances, you can just leave your subclass in place.
STATUS
======
This behavior is by design.
MORE INFORMATION
================
The Visual Basic Help topic for the Deactivate event explains the following:
"If an .exe file built by Visual Basic displays a dialog box created by a
.dll file also built in Visual Basic, the .exe file's form will get the
Deactivate and LostFocus events. This may be unexpected, because you should
not get the Deactivate event:
- If the object is an out-of-process component.
- If the object isn't written in Visual Basic.
- In the development environment when calling a DLL built in Visual Basic."
This documentation is a little misleading and should state the following
instead:
"You should not get a Deactivate event if the focus is changed to another
form that is not part of the VB Project containing the form that currently
has the focus."
Steps to Reproduce Behavior
---------------------------
1. Create a new ActiveX DLL project in Visual Basic. From the Project Menu,
select Add Form.
2. Add a Label to the new for,m and set the Caption to the following:
Non-modal ActiveX form
3. Add the following code to the Form_Deactivate:
Beep
4. Change the Name of the Form to "frmActiveX" (without the quotation marks).
5. Change the name of Class1 to "FormClass" (without the quotation marks).
6. Change the name of the Project to "FormPrb" (without the quotation marks).
7. Add the following code the class module:
Public Sub ShowForm()
frmActiveX.Show 0 'show it modeless
End Sub
8. Save the Project, and then choose Make FormPrb.DLL from the File menu.
9. From the File Menu, select New Project, and then select Standard EXE.
10. Add a CommandButton to the Form.
11. Add the following code to the Form:
Dim oFormPrb As Object
Private Sub Command1_Click()
oFormPrb.showform
End Sub
Private Sub Form_Deactivate()
Beep
End Sub
Private Sub Form_Load()
Set oFormPrb = CreateObject("FormPrb.formclass")
End Sub
12. Run the Form and then click the CommandButton.
13. Try moving between the two forms.
NOTE: The Beep in the Form_Deactivate does not fire. However, the title bar
of forms changes to show which form has the focus.
REFERENCES
==========
For more information, please see the following articles in the Microsoft
Knowledge Base:
Q170570 HOWTO: Build a Windows Message Handler with AddressOf in VB5
Q168795 HOWTO: Hook Into a Window's Messages Using AddressOf
Additional query words: KBAutomation kbActiveX KBComp KBDLL kbVBp kbdsd kbDSupport kbVBp500bug kbVBp600bug kbVBA
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Keywords : kbGrpDSVB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Issue type : kbbug kbprb
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