Книга: Beginning Android

Menu Options and XML

Menu Options and XML

Inside the item and group elements you can specify various options, matching up with corresponding methods on Menu or MenuItem.

The title of a menu item is provided via the android:title attribute on an item element. This can be either a literal string or a reference to a string resource (e.g., @string/foo).

Menu items can have icons. To provide an icon — in the form of a reference to a drawable resource (e.g., @drawable/eject), use the android:icon attribute on the item element.

By default, the order of the items in the menu is determined by the order they appear in the menu XML. If you want, you can change that default by specifying the android:orderInCategory attribute on the item element. This is a 0-based index of the order for the items associated with the current category. There is an implicit default category; groups can provide an android:menuCategory attribute to specify a different category to use for items in that group.

Generally, though, it is simplest just to put the items in the XML in the order you want them to appear.

Items and groups can be enabled or disabled, controlled in the XML via the android:enabled attribute on the item or group element. By default, items and groups are enabled. Disabled items and groups appear in the menu but cannot be selected. You can change an item’s status at runtime via the setEnabled() method on MenuItem, or change a group’s status via setGroupEnabled() on Menu.

Similarly, items and groups can be visible or invisible, controlled in the XML via the android:visible attribute on the item or group element. By default, items and groups are visible. Invisible items and groups do not appear in the menu at all. You can change an item’s status at runtime via the setVisible() method on MenuItem, or change a group’s status via setGroupVisible() on Menu.

In the layout XML shown earlier, the other_stuff group is initially invisible. If we make it visible in our Java code, the two menu items in the group will “magically” appear.

Items can have shortcuts — single letters (android:alphabeticShortcut) or numbers (android:numericShortcut) that can be pressed to choose the item without having to use the touch screen, D-pad, or trackball to navigate the full menu.

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