如何检测弹出菜单的子菜单弹出(以及如何动态填充)?

标准菜单或上下文(弹出)菜单中的子菜单之间没有区别:如果菜单项附加了子菜单,则其 OnClick 事件将在子菜单显示之前触发(请注意,不需要单击它即可显示),在该事件处理程序中,您可以修改子菜单(设置现有项的属性,或添加新项/删除现有项)。

一些关于动态添加和删除项目的演示代码:

procedure TForm1.FormCreate(Sender: TObject);
var
  Popup: TPopupMenu;
  Item, SubItem: TMenuItem;
begin
  Popup := TPopupMenu.Create(Self);
  PopupMenu := Popup;
  Item := TMenuItem.Create(Popup);
  Item.Caption := 'Test submenu';
  Item.OnClick := PopupClick;
  Popup.Items.Add(Item);

  SubItem := TMenuItem.Create(Item);
  SubItem.Caption := 'dummy';
  Item.Add(SubItem);
end;

procedure TForm1.PopupClick(Sender: TObject);
var
  SubmenuItem, Item: TMenuItem;
begin
  SubmenuItem := Sender as TMenuItem;
  // delete old items (leave at least one to keep the submenu)
  while SubmenuItem.Count > 1 do
    SubmenuItem.Items[SubmenuItem.Count - 1].Free;
  // create new items
  while SubmenuItem.Count < 3 do begin
    Item := TMenuItem.Create(SubmenuItem);
    Item.Caption := Format('new item created %d', [GetTickCount]);
    SubmenuItem.Add(Item);
  end;
end;