<ol> * <li><b>Context menus</b>: Do not support item shortcuts and item icons. * <li><b>Options menus</b>: The <b>icon menus</b> do not support item check * s and only show the item's * {@link MenuItem#setTitleCondensed(CharSequence) condensed title}. The * <b>expanded menus</b> (only available if six or more menu items are visible, * reached via the 'More' item in the icon menu) do not show item icons, and * item check s are discouraged. * <li><b>Sub menus</b>: Do not support item icons, or nested sub menus. * </ol>
* <li><b>Context menus</b>: Do not support item shortcuts and item icons.
* <li><b>Options menus</b>: The <b>icon menus</b> do not support item check
* s and only show the item's
* {@link MenuItem#setTitleCondensed(CharSequence) condensed title}. The
* <b>expanded menus</b> (only available if six or more menu items are visible,
* reached via the 'More' item in the icon menu) do not show item icons, and
* item check s are discouraged.
* <li><b>Sub menus</b>: Do not support item icons, or nested sub menus.
* </ol>
既然什么都没有实现,那为什么不做成接口?还有这里的mParent什么时候会不等于NULL?