Programming Forums > Application Development > Visual Basic

cloud- · Aug 10th, 2005, 2:02 PM

well,.. I have an mdi form with a few menus...one of these menus happenes to be what forms/windows are in view. When the child forms are unloaded they obviously need to be unchecked from the view, but when using:

(Toggle Plain Text)

private sub childform_unload()
frmmain.menuthiswindow.checked = false
end sub

I get the error message:

(Toggle Plain Text)

Only one MDI form allowed.

all i want to do is make the child form change the check status for a menu in the main form.

anyone know how i can do this?

thanks

BrianN · Aug 11th, 2005, 1:03 PM

Are you saying that you want to make it so that it has a list of all the forms and then the checkmark is on the form that has to focus?

Or do you have a certain child forms that appear in the menu and you want the checks to appear on the forms that are visible?

Rory · Aug 11th, 2005, 1:43 PM

It's possible that frmMain is not actually loaded when this event fires, and get/setting a property would cause VB to actually load and create a new instance of the (MDI) form, hence your error (as opposed to raising an error like in any other sane language!). Try debugging on step thru or setting a break point on that event to see when it is raised

cloud- · Aug 11th, 2005, 2:28 PM

hi the error only happens when i try to change the main forms menu check status with one of its child forms events (unload)

and heres pictures to explain what i mean

^--- when i click the checks the windows show/hide and boxes are checked for show and unchecked for hide...

V--- i need to make the check disappeer if the window is closed with the X but i always get the error:

the menu is in the main form but i need to change it from the child form...
i can use other functions in the unload event and not get an error message.

how can i get round this problem?

+ thanks alot for your replys! ^^;;

Rory · Aug 11th, 2005, 2:48 PM

Unlike normal forms, I don't think child forms can access the MDI form they are in by name, so VB is trying to create a new instance for you, hence the error. Try accessing the Me.Parent object within the child form, or if not, declare a global boolean ChildFormVisible in a module somewhere. Or better still, move the code to the mnuView_Click or mnuView_Popup event, then you'd just need an If ChildForm.visible then somemenuitem.Checked=true line

BrianN · Aug 11th, 2005, 4:02 PM

well I have not been able to replicate your error message. Here is the code i tried.

My menu items were created using the menu editor provided in visual basic (not dynamically created at runtime)

First off the code for the menu items is like this:

(Toggle Plain Text)

Public Sub mnuform1_Click()
    If mnuform1.Checked = True Then
        Unload Form1
        mnuform1.Checked = False
    Else
        Load Form1
        mnuform1.Checked = True
    End If
End Sub

Take note to how i changed it from private to public

Next the unload code on the forms is like this:

(Toggle Plain Text)

Private Sub Form_Unload(Cancel As Integer)
     Call MDIForm1.mnuform1_Click
End Sub

Note when the program loads you are going to have to use the mdiform1.mnuform1.checked=true (or false) depending on what forms are shown to begin with.

I only spent about five minutes writing up this code, so I am sure that there are going to be several problems with it depending on what you are going to do with it. I can think of a few right now, but i won't go into details with them. (I am sure there are solutions to solving all of them)

cloud- · Aug 11th, 2005, 4:39 PM

hey thanks rory but could you possibly give me a short example of how i can get something like you mentioned before, i don't quite understand how i can do that. i tryed making a function in a module...didnt work though all though maybe i misunderstood XD.
and im not sure what u meant by the 3rd solution...the menu click command can't take in to account the unload of the child form can it ?__?; because the problem is only the X button on the form.

please help

thanks

Rory · Aug 15th, 2005, 6:09 PM

Quote:

Originally Posted by cloud-

hey thanks rory but could you possibly give me a short example of how i can get something like you mentioned before, i don't quite understand how i can do that. i tryed making a function in a module...didnt work though all though maybe i misunderstood XD.
and im not sure what u meant by the 3rd solution...the menu click command can't take in to account the unload of the child form can it ?__?; because the problem is only the X button on the form.

please help

thanks

Right, the problem is most likely accessing the checked property of a non-existent MDI form. Try approaching it from the other angle: if you had a menu called mnuView, the mnuView_Click() event fires before the menu is pulled down, giving you a change mnuView's appearence itself. So I'd suggest something along the lines of :

(Toggle Plain Text)

Private Sub mnuView_Click()
If Not (frmProjectWindow Is Nothing) Then ' Check if the form has been loaded
    If frmProjectWindow.Visible Then ' Check if the form is visible
        mnuViewProjectWindow.Checked = True ' Form is loaded and visible
    Else
        mnuViewProjectWindow.Checked = False
    End If
Else
    mnuViewProjectWindow.Checked = False
End If
End Sub

cloud- · Aug 19th, 2005, 5:24 AM

BrianN: sorry i didn't see your code before. I still go the error message by using that

.

Rory: I tried that and when i click on the form menu it just makkes the form visible, and always stays checked.

thanks for helping guys.
any ideas to what im doing wrong?

Rory · Aug 23rd, 2005, 2:03 PM

Quote:

Originally Posted by cloud-

Rory: I tried that and when i click on the form menu it just makkes the form visible, and always stays checked.

Really strange - could you upload the source code?

Aug 10th, 2005, 2:02 PM	#1
cloud- Hobbyist Programmer Join Date: Jan 2005 Posts: 110 Rep Power: 4	MDI forms - menu trouble well,.. I have an mdi form with a few menus...one of these menus happenes to be what forms/windows are in view. When the child forms are unloaded they obviously need to be unchecked from the view, but when using: (Toggle Plain Text) private sub childform_unload() frmmain.menuthiswindow.checked = false end sub private sub childform_unload() frmmain.menuthiswindow.checked = false end sub I get the error message: (Toggle Plain Text) Only one MDI form allowed. Only one MDI form allowed. all i want to do is make the child form change the check status for a menu in the main form. anyone know how i can do this? thanks

Aug 11th, 2005, 4:02 PM	#6
BrianN Newbie Join Date: Aug 2005 Posts: 6 Rep Power: 0	well I have not been able to replicate your error message. Here is the code i tried. My menu items were created using the menu editor provided in visual basic (not dynamically created at runtime) First off the code for the menu items is like this: (Toggle Plain Text) Public Sub mnuform1_Click() If mnuform1.Checked = True Then Unload Form1 mnuform1.Checked = False Else Load Form1 mnuform1.Checked = True End If End Sub Public Sub mnuform1_Click() If mnuform1.Checked = True Then Unload Form1 mnuform1.Checked = False Else Load Form1 mnuform1.Checked = True End If End Sub Take note to how i changed it from private to public Next the unload code on the forms is like this: (Toggle Plain Text) Private Sub Form_Unload(Cancel As Integer) Call MDIForm1.mnuform1_Click End Sub Private Sub Form_Unload(Cancel As Integer) Call MDIForm1.mnuform1_Click End Sub Note when the program loads you are going to have to use the mdiform1.mnuform1.checked=true (or false) depending on what forms are shown to begin with. I only spent about five minutes writing up this code, so I am sure that there are going to be several problems with it depending on what you are going to do with it. I can think of a few right now, but i won't go into details with them. (I am sure there are solutions to solving all of them)

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Aug 11th, 2005, 1:03 PM	#2
BrianN Newbie Join Date: Aug 2005 Posts: 6 Rep Power: 0	Are you saying that you want to make it so that it has a list of all the forms and then the checkmark is on the form that has to focus? Or do you have a certain child forms that appear in the menu and you want the checks to appear on the forms that are visible?

Aug 11th, 2005, 1:43 PM	#3
Rory Expert Programmer Join Date: Jan 2005 Location: London Posts: 542 Rep Power: 4	It's possible that frmMain is not actually loaded when this event fires, and get/setting a property would cause VB to actually load and create a new instance of the (MDI) form, hence your error (as opposed to raising an error like in any other sane language!). Try debugging on step thru or setting a break point on that event to see when it is raised

Aug 11th, 2005, 2:28 PM	#4
cloud- Hobbyist Programmer Join Date: Jan 2005 Posts: 110 Rep Power: 4	hi the error only happens when i try to change the main forms menu check status with one of its child forms events (unload) and heres pictures to explain what i mean ^--- when i click the checks the windows show/hide and boxes are checked for show and unchecked for hide... V--- i need to make the check disappeer if the window is closed with the X but i always get the error: the menu is in the main form but i need to change it from the child form... i can use other functions in the unload event and not get an error message. how can i get round this problem? + thanks alot for your replys! ^^;;

Aug 11th, 2005, 2:48 PM	#5
Rory Expert Programmer Join Date: Jan 2005 Location: London Posts: 542 Rep Power: 4	Unlike normal forms, I don't think child forms can access the MDI form they are in by name, so VB is trying to create a new instance for you, hence the error. Try accessing the Me.Parent object within the child form, or if not, declare a global boolean ChildFormVisible in a module somewhere. Or better still, move the code to the mnuView_Click or mnuView_Popup event, then you'd just need an If ChildForm.visible then somemenuitem.Checked=true line

Aug 11th, 2005, 4:39 PM	#7
cloud- Hobbyist Programmer Join Date: Jan 2005 Posts: 110 Rep Power: 4	hey thanks rory but could you possibly give me a short example of how i can get something like you mentioned before, i don't quite understand how i can do that. i tryed making a function in a module...didnt work though all though maybe i misunderstood XD. and im not sure what u meant by the 3rd solution...the menu click command can't take in to account the unload of the child form can it ?__?; because the problem is only the X button on the form. please help thanks

Aug 19th, 2005, 5:24 AM	#9
cloud- Hobbyist Programmer Join Date: Jan 2005 Posts: 110 Rep Power: 4	BrianN: sorry i didn't see your code before. I still go the error message by using that . Rory: I tried that and when i click on the form menu it just makkes the form visible, and always stays checked. thanks for helping guys. any ideas to what im doing wrong?

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Programming Forums > Application Development > Visual Basic

MDI forms - menu trouble