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Catching createing and death of MDI child form.

Posted on 2004-12-01
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Last Modified: 2010-04-05
How can I catch createing and death of MDI child form on parent (MDI) form.

Have a MainForm:TMainForm with FormStyle property set to fs MDIForm. I need to know when child form (the form with FormStyle property set to fs MDIChild) created or destroyed.
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Question by:lmikle
5 Comments
 
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Accepted Solution

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paulb1989 earned 172 total points
ID: 12720324
In the MDIChild forms unit, add this AFTER implementation:

    uses Form1;

Replace Form1 with the name of the unit with your MDIForm in it.

Now make an event for the oncreate and ondestroy events of the MDIChild form, and in there you can now reference to your main form.

eg:

   procedure MyMDIChildCreate(Sender: TObject);
   begin
     Form1.DoSomething;
   end;

You can then make a procedure on your main form and call it when the MDIChild is created or destroyed.
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by:lmikle
ID: 12720433
OK. Sorry for inaccuracy.

In a main form I do some work dependencing on MDIChildren list. In child form's OnDestroy it steel contain one and I can't do this work correctly.
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LVL 13

Expert Comment

by:BlackTigerX
ID: 12721057
you always know when the form is created because you create it right?

if you have it in the autoCreate forms, then it will happen at the very beginning of the application, if you create it in some event (when clicking a button or something) then at that point you create it, and  you can take the other action you need to do at that point, for destroy the form you can use what paulb1989 suggested, just call a method of the main form from the Child form
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LVL 27

Assisted Solution

by:kretzschmar
kretzschmar earned 164 total points
ID: 12723556
usual you can define a function or procedure in the mainform,
which is called from the mdichild in the onCloseQuery, onClose or onDestroy

i would prefer the onClose event, because a mdichild should have
a eventproc already

sample

//procedure in mainform
Procedure TMainForm.ChildClose(AChild : TForm);
begin
  //do your stuff here
end;

in you onClose-event of your child

...
begin
  MainForm.ChildClose(self);  
  action := caFree;
end;

to get this work you must include the mainform unit after the implementation-keyword into the uses clause.

meikl ;-)
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LVL 17

Assisted Solution

by:Wim ten Brink
Wim ten Brink earned 164 total points
ID: 12724826
I wonder if you could use the protected method
    procedure Notification( AComponent: TComponent; Operation: TOperation ); override;

Basically, this method is called whenever a component is added or removed from your form. However, AComponent might not be fully initialized at this moment and it will get triggered for every component on your form. But it will get triggered when you create a childform using the syntax:
  ChildForm := TChildForm.Create(ParentForm);

So I think you could just override this method, call the inherited method first, then check if a form is added or removed.
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