数据库字段内容如何在DBGRID的单元格中被改写显示？

Question

在Query1的HappenDate字段的GetText事件中～～procedure Query1HappenDateGetText(Sender: TField;
  var Text: String; DisplayText: Boolean);
begin
  if (DisplayText) then
  begin
    if Sender.AsString = Null then Text := '2002-01-01'
  end
  else
    Text := Sender.AsString;
end;

Answer 1

或者是procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
begin
  if ADOQuery1.FieldByName('ID').AsString=Null then
    DBGrid1.Canvas.TextOut(Rect.Left,Rect.Top,'2002-01-01');
end;