FIX: Hidden MDIChild Form Can Still Be Active Form

ID: Q150195

The information in this article applies to:

Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0

SYMPTOMS

Under certain circumstances, an MDIChild form can be hidden but still be the active form. This occurs when an MDIChild form is shown before hiding the active MDIChild form. The latter MDIChild form stays active although it is invisible. Clicking in an area of the invisible form does not activate a visible form behind it because the input is sent to the invisible form.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been fixed in Visual Basic 6.0.

WORKAROUND

If you are going to hide an MDIChild form and then show another form, it is important to hide the existing form first, and then show the new MDIChild form.

For example, instead of the code:


   Form3.Show

   Me.Hide

the following code accomplishes the same objective but avoids the problem described above:


   Me.Hide

   Form3.Show

MORE INFORMATION

Steps to Reproduce Problem

Start a new project in Visual Basic. Form1 is created by default. Select the Insert/Form menu option twice and insert an MDI parent form by selecting Insert/MDI Form.

Change the MDIChild property of all three regular forms to True. Place a Command button on Form1 and Form2. In the Click event of the Command button on Form1, place the following code:
```
   Private Sub Command1_Click()

      Form2.Show

   End Sub 
```

In the Click event of the Command button on Form2, place the following code:


   Private Sub Command1_Click()

     Form3.Show

     Me.Hide

   End Sub

Run the project by pressing the F5 key. Click on the Command button of Form1 to show Form2. Move Form2 so it only partially covers Form1. For example, have it cover the lower right hand corner of Form1. Click on the Command button on Form2 to show Form3 and hide Form2. Click on the lower right hand corner of Form1. Form1 is not activated.

To correct this problem, change the code in the Click event of the Command button on Form2 to read:


   Private Sub Command1_Click()

      Me.Hide

   Form3.Show

   End Sub

Additional query words: kbVBp400bug kbVBp500fix kbVBp kbdsd kbDSupport kbNoKeyWord

Keywords : kbGrpVB
Version :
Platform : NT WINDOWS
Issue type : kbbug