Title: Playing with style - Part 2
Question: I need a quick way to make a TEdit accepts only numeric charaters. How?
Answer:
You can obtain this result by adding the ES_NUMBER style to the edit field ones. Try this:
procedure NumericOnly(theEdit: TEdit);
var
dwStyle: Longint;
begin
dwStyle := GetWindowLong(theEdit.Handle, GWL_STYLE) or ES_NUMBER;
SetWindowLong(theEdit.Handle, GWL_STYLE, dwStyle);
end;
Important: With this style set, the edit field accepts only numeric characters; this mean that you cannot use dots, hyphens or any other punctuation mark!!!
Of course you can derive a numeric only edit field from the base class TEdit in this way:
unit NumericEdit;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;
type
TNumericEdit = class(TEdit)
private
{ Private declarations }
protected
{ Protected declarations }
procedure CreateParams(var Params: TCreateParams); override;
public
{ Public declarations }
published
{ Published declarations }
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('Bigpepe', [TNumericEdit]);
end;
{ TNumericEdit }
procedure TNumericEdit.CreateParams(var Params: TCreateParams);
begin
inherited;
Params.Style := Params.Style or ES_NUMBER;
end;
end.
Is important to keep in mind that even if the derived control accepts only numeric characters, you can still set its Text property to any alphanumeric value.
Enjoy!