@@@我想从TDBGrid继承一个子类,可以实现奇偶行的颜色交替,但遇到了问题,请大家帮忙看看@@@(50分)

    property SelectedCellBackColor: TColor read FSelectedCellBackColor
      write SetSelectedCellBackColor [b]default[/b] clHighlight;
    property SelectedCellFontColor: TColor read FSelectedCellFontColor
      write SetSelectedCellFontColor [b]default[/b] clHighlightText;
    property FirstAlternateColor: TColor read FFirstAlternateColor
      write SetFirstAlternateColor [b]default[/b] clSkyBlue;
    property SecondAlternateColor: TColor read FSecondAlternateColor
      write SetSecondAlternateColor [b]default[/b] clWhite;

procedure TColorDBGrid.DrawColumnCell(const Rect: TRect; DataCol: Integer;
  Column: TColumn; State: TGridDrawState);
begin
  inherited;
  if ((State = [gdSelected]) or (State = [gdSelected, gdFocused])) then
  begin
    Canvas.Brush.Color := ColorSelectedCellBack;
    Canvas.Font.Color := ColorSelectedCellFont;
  end
  else begin
    if DataSource.DataSet.RecNo mod 2 <> 0 then
      Canvas.Brush.Color := ColorAlternateFirst
    else
      Canvas.Brush.Color := ColorAlternateSecond;
  end;
  DefaultDrawColumnCell(Rect, DataCol, Column, State);
end;

constructor TColorDBGrid.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FColorSelectedCellBack := clHighlight;
  FColorSelectedCellFont := clHighlightText;
  FColorAlternateFirst := $00F2F2F2;
  FColorAlternateSecond := clWhite;
end;