为窗口添加菜单

（1）程序功能：在窗口中添加菜单栏，在菜单栏添加菜单项，并添加下拉菜单和 2 级菜单，通过选择 菜单项可以执行不同操作，如“打开”可打开 LX6_6 类生成的窗口。

-To add menu window



Functions: (1) program in the window to add menu bar, the menu bar to add a menu item, and add the drop-down menu and level 2, by selecting a menu item can perform different operations, such as "open" to open LX6_6 class generated by the window.