现在使用控件, 更喜欢继承
以前写代码, 总是把主单元弄得满满当当; 现在更喜欢把控件比较独立的功能写成一个单元, 改写属性、重载方法...哪怕只有一点点和默认不同, 也喜欢独立出来.
刚刚用到 TListBox, 需要能拖动元素、双击删除.
unit ListBox2; interface uses System.Classes, Vcl.Controls, Vcl.StdCtrls, System.Types; type TListBox2 = class(TCustomListBox) protected procedure DragOver(Source: TObject; X: Integer; Y: Integer; State: TDragState; var Accept: Boolean); override; procedure DblClick; override; public constructor Create(AOwner: TComponent); override; procedure DragDrop(Source: TObject; X: Integer; Y: Integer); override; end; implementation { TListBox2 } constructor TListBox2.Create(AOwner: TComponent); begin inherited; DragMode := dmAutomatic; end; procedure TListBox2.DblClick; begin inherited; Items.Delete(ItemIndex); end; procedure TListBox2.DragDrop(Source: TObject; X, Y: Integer); begin inherited; Items.Exchange(ItemIndex, ItemAtPos(Point(X,Y), True)); end; procedure TListBox2.DragOver(Source: TObject; X, Y: Integer; State: TDragState; var Accept: Boolean); begin inherited; Accept := True; end; end.
测试:
uses ListBox2; procedure TForm1.FormCreate(Sender: TObject); begin with TListBox2.Create(Self) do begin Parent := Self; Align := alLeft; Items.CommaText := 'A,B,C,D,E,F,G'; end; end;