if not TryStrToInt(Edit1.text, angka) then 
   edit1.text := '';

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
  if not (key in ) then key:=#0;
end;

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
  if not (key in ) then 
    key:=#0;
end;

@khairulfahmi: klo inputnya pake double bisa g?? ada koma komanya gt:-)

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
  if not (key in ) then 
    key:=#0;
end;