I get this error when I drop my control on a form. The error appears here:
TAssociateFileExt = class(TGroupBox)
private
protected
public
btnAssociate : TButton;
constructor Create(aOwner: TComponent); override;
end;
constructor TAssociateFileExt.Create(aOwner: TComponent);
begin
inherited Create(aOwner);
Caption:= ''; <-------- error here
ClientHeight:= 125; <-------- and here
ClientWidth := 170;
DoubleBuffered:= TRUE;
btnAssociate:= TButton.Create(Self);
btnAssociate.Parent:= Self;
btnAssociate.Visible:= TRUE;
btnAssociate.Left:= 17;
btnAssociate.Top:= 26;
btnAssociate.Width:= 142;
btnAssociate.Height:= 25;
btnAssociate.Hint:= 'Associate this application with its files. When you double click a file this program will automatically start and load that file.';
btnAssociate.Caption:= 'Associate';
btnAssociate.DoubleBuffered:= TRUE;
btnAssociate.ParentDoubleBuffered:= FALSE;
btnAssociate.TabOrder:= 0;
btnAssociate.OnClick:= btnAssociateClick;
btnAssociateDel:= TButton.Create(Self);
btnAssociateDel.Parent:= Self;
btnAssociateDel.Visible:= TRUE;
btnAssociateDel.Left:= 17;
btnAssociateDel.Top:= 53;
btnAssociateDel.Width:= 142;
btnAssociateDel.Height:= 25;
btnAssociateDel.Hint:= 'Remove association';
btnAssociateDel.Caption:= 'Remove association';
btnAssociateDel.DoubleBuffered:= TRUE;
btnAssociateDel.ParentDoubleBuffered:= FALSE;
btnAssociateDel.TabOrder:= 1;
btnAssociateDel.OnClick:= btnAssociateDelClick;
chkAllUsers:= TCheckBox.Create(Self);
chkAllUsers.Parent:= Self;
chkAllUsers.Visible:= TRUE;
chkAllUsers.Left:= 31;
chkAllUsers.Top:= 97;
chkAllUsers.Width:= 115;
chkAllUsers.Height:= 17;
chkAllUsers.Hint:= 'Please note that if you want to do this for all users then you need administrator/elevated rights.';
chkAllUsers.Caption:= 'Do this for all users';
chkAllUsers.DoubleBuffered:= TRUE;
chkAllUsers.ParentDoubleBuffered:= FALSE;
chkAllUsers.TabOrder:= 2;
chkAllUsers.OnClick:= chkAllUsersClick;
end;
Probably the answer is 'Caption needs a valid window handle'. Right? However, an article by David Intersimone (here) says it is ok to set Caption in the constructor.
Update:
After adding (aOwner: TComponent), as J... suggested, to constructor's declaration (in Implementation) the error moved to the next line (clientheight:= 90);
I moved the code in CreateWindowHandle. Now it works. Full code:
UNIT cAssociateExt;
INTERFACE
USES
Windows, Messages, SysUtils, Classes, Controls, ExtCtrls, Forms, StdCtrls;
TYPE
TAssociateFileExt = class(TGroupBox)
private
protected
public
btnAssociate : TButton;
btnAssociateDel: TButton;
chkAllUsers : TCheckBox;
constructor Create(aOwner: TComponent); override;
procedure AfterConstruction; override;
procedure CreateWindowHandle(const Params: TCreateParams); override;
...
published
end;
procedure Register;
IMPLEMENTATION
procedure TAssociateFileExt.AfterConstruction;
begin
inherited; //Not a good place here
end;
procedure TAssociateFileExt.CreateWindowHandle(const Params: TCreateParams);
begin
inherited;
//DO NOT CREATE CONTROLS HERE! See: Sertac Akyuz's comment
Caption:= '';
ClientHeight:= 125;
ClientWidth := 170;
end;
constructor TAssociateFileExt.Create(aOwner: TComponent);
begin
inherited Create(aOwner);
DoubleBuffered:= TRUE;
btnAssociate:= TButton.Create(Self);
btnAssociate.Parent:= Self;
btnAssociate.Visible:= TRUE;
btnAssociate.Left:= 17;
...
end;
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