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Error in ListView Columns

Posted on 1998-07-26
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Medium Priority
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Last Modified: 2010-04-04
I Create a Component as follows:

-------
type
  TMyListView = class(TCustomListView)
...

constructor TMyListView.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  ViewStyle:=vsReport;
  With Columns.Add do Caption:='AAA';
end;
------

But when I try to put this component on a form (in design) I get an error: 'Control '' doesn't have a parent window'
This happens on the line:   With Columns.Add do Caption:='AAA';
Any ideas?
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Question by:ronit051397
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3 Comments
 
LVL 2

Expert Comment

by:freter
ID: 1358719
Right. This error occurs due to the fact that at the moment of executing the line "with columns.add do caption := 'AAA'; ", windows hasn't created the handle for your control yet. I experienced this behaviour myself quite often in my early days ;-)
Here's how to avoid it:
>>>>>>>>>
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, comctrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

type
  TMyListView = class(TCustomListView)
  private
    procedure CreateWnd; override;
  public
    constructor Create(AOwner: TComponent); override;
  end;
var
  Form1: TForm1;

implementation

{$R *.DFM}



constructor TMyListView.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  ViewStyle:=vsReport;
end;

procedure TMyListView.CreateWnd;
begin
  inherited;
  With Columns.Add do Caption:='AAA';
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  with TMyListView.Create(self) do begin
    parent := self;
    left := 10;
    top := 10;
    visible := true;
  end;
end;

end.

<<<<<<<<<<<<<<<<<<
Don't forget to place a button named Button1 on your form an assign the event Button1CLick to it's click event.

Regards,
Freter

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LVL 5

Author Comment

by:ronit051397
ID: 1358720
Many thanks,
If you post an answer I'll grade it.

Ronit,
0
 
LVL 2

Accepted Solution

by:
freter earned 200 total points
ID: 1358721
Hi Ronit!
I hope it helped you. Here is the answer to grade.

Keep smiling ;-)
Freter
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