Adding TabSheets to PageControl component

I want to make a pagecontrol component with several tabsheets on it.
When I try to place it on a form, I get an error "Control '' has not parent window".

His is my Create method for the pagecontrol component.

begin
 inherited Create(AOwner);
 Height   := 280;
 Width    := 580;
 tbsPage1 := TTabSheet.create(Self);
 tbsPage1.PageControl := Self;
end;

As soon as I add the .PageControl line of code, I can no longer add the component to any forms.
What am I doing wrong?
LVL 1
dclAsked:
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ITugayConnect With a Mentor Commented:
hi all.


dcl, the problem is that you can't insert TTabSheet in TPageControl while it have no parent defined. The parent will be defined only after parent of TPageControl calls method InsertControl. To hook this moment I suggest you detect CM_PARENTCTL3DCHANGED command. This command occurs when parent to TPageControl calls self InsertControl method.
Try code bellow, it' works.

-------
type
  TMyPageControl = class(TPageControl)
    tbsPage1 : TTabSheet;
    constructor Create(aOwner : TComponent); override;
    procedure   WndProc(var MSG : TMessage); override;
  end;

constructor TMyPageControl.Create(aOwner : TComponent);
begin
 inherited Create(AOwner);
 Height   := 280;
 Width    := 380;
end;

procedure   TMyPageControl.WndProc(var MSG : TMessage);
begin
  inherited;
  if (MSG.MSG = CM_PARENTCTL3DCHANGED)
  and (tbsPage1 = nil) then  // prevent duplicate initialization
  begin
   tbsPage1 := TTabSheet.create(Self);
   tbsPage1.PageControl:=Self;
   tbsPage1.Caption:='000';
  end;
end;

// use it as test to be sure it work
procedure TForm1.SpeedButton1Click(Sender: TObject);
begin
  TM := TMyPageControl.Create(Self);
  InsertControl(TM);
end;

----
Igor
0
 
kretzschmarCommented:
hi dcl,

you must set a parent for the pagecontrol and the tabsheet.

we´ll, the parent for the pagecontrol is done in the inheritance-call.

guessing u must only set the parent for the tabsheet. try this change:

begin
 inherited Create(AOwner);
 Height   := 280;
 Width    := 580;
 tbsPage1 := TTabSheet.create(Self);
 tbsPage1.PageControl := Self;
 tbsPage1.Parent      := Self;
end;

meikl
0
 
dclAuthor Commented:
Adjusted points from 50 to 100
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dclAuthor Commented:
Thanks ITugay

I would never have found that!

I expect to have more questions soon.
0
 
ITugayCommented:
always welcome;)
0
 
dclAuthor Commented:
Igor,
Is it the parent's InsertControl method that is being run, or the PageControls?
I am trying to fnd a place I can call a "AddPages" method to a PageControl Class, to make this easy next time
0
 
ITugayCommented:
Well, in my sample I have detected a moment when parent of PageControl calls it's method InsertControl. I mean "parent" is for example TForm where TPageControl have placed.

//TForm.InsertControl(PageControl)

At first sight it would be necessary to override TPageControl.SetParent method, but InsertControl doesn't call it.

The sample I showed you not seems like a right way to add page to PageControl, it look like some trick, but it work. The deal is that TTabSheet is inherits from TWinControl, and had be added inside TPageControl.Constructor but TPageControl have different  from usual mechanism to insert controls (add pages). It tries to make a page visible just after TTabSheet.PageControl property have been assigned. And error occurs when it tries to make control visible without right chain of parents.

To make it easy.... Ok, I shall think about, and let you know when be ready.
----
Igor.
0
 
dclAuthor Commented:
Thanks for your time Igor
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