Q190634: PRB: Activate Event Is Not Triggered with Child Form of MDI Form

Article: Q190634
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): kbGrpDSVBDB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

The Activate event for an MDIChild form is only triggered the first time the
form is shown. For example, when an MDIChild form is displayed using the Show
Method, then hidden using the Hide method, and then shown again using the Show
method, the Activate event is triggered only the first time the form is shown.

CAUSE
=====

The Activate and Deactivate events occur for MDI child forms only when the focus
changes from one child form to another. In an MDIForm object with two child
forms, the child forms receive these events when the focus moves between them.
However, when the focus changes between a child form and a non-MDI child form,
the parent MDIForm receives the Activate and Deactivate events.

RESOLUTION
==========

To work around this behavior, create a custom method in Form1 to handle showing
the form. In the custom method, place code to show the form as well as code you
would have placed in the Activate event. To display the child form, call the
custom method instead of using the form's Show method. An example custom method
to show a child form and simulate an Activate event would be:

     Public Sub MyShow()
        Form1.Show
        MsgBox "MyShow - simulation of Activate event"
     End Sub

The call to invoke this custom method would be:

     Form1.MyShow  'Call the custom method created in Form1

STATUS
======

This behavior is by design.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. Create a new standard EXE project. Form1 is created by default.

2. Choose Project, Add MDI Form, to add an MDI form.

3. Choose Project, Project1 Properties, and then set MDIForm1 to be Project1's
  Startup Object.

4. Select Form1 and change the Name and Caption properties of Form1 to frmChild.
  Set frmChild's MDIChild property to True.

5. In the Activate event of frmChild, place the following code:

        MsgBox "MDIChild Activate Event"

6. Place a CommandButton on frmChild. In the Click event for the CommandButton,
  place the following code:

        Me.Hide

7. Select MDIForm1 (the parent form). Open the Visual Basic Menu Editor to place
  a menu item on the MDI form. Set the Caption of the menu item to "Show
  MDIChild." Set the Name of the menu item to "mnuShow." In the Click event for
  the mnuShow menu item, place the following code:

         rmChild.Show

8. Press the F5 key to run the application. Click the Show MDIChild menu item.
  The message box appears as the child form is displayed. Click the
  CommandButton on frmChild to hide the child. Click the Show MDIChild menu
  item again. The message box does not appear, indicating that the MDIchild's
  Activate event did not fire.

9. Select frmChild. Open the form's code window and place the following
  workaround code:

        Public Sub MyShow()
           Me.Show
           MsgBox "MyShow acting as Activate event"
        End Sub

10. Select MDIForm1. In the Click event for the mnuShow menu item, replace the
  previous code with:

        frmChild.MyShow

11. Press the F5 key to run the application. Click the Show MDIChild menu item.
  The message box appears as the child form is displayed. Click the
  CommandButton on frmChild to hide the child. Click the Show MDIChild menu
  item again. The message box appears again.

REFERENCES
==========

For documentation on this behavior, search for "Activate event" in Visual Basic
Online Help Index. Select "Activate,Deactivate Events."

Additional query words: kbMDI kbVBp600 kbVBp500 kbdse kbDSupport kbVBp

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Keywords          : kbGrpDSVBDB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Issue type        : kbprb

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