Swing Menus and Toolbars - The Definitive Guide to Java Swing - page 162

public class MenuKeyEvent extends KeyEvent {
public MenuKeyEvent(Component source, int id, long when, int modifiers,
int keyCode, char keyChar, MenuElement path[], MenuSelectionManager mgr);
public MenuSelectionManager getMenuSelectionManager();
public MenuElement[] getPath();
}
It's the job of the MenuSelectionManager to determine the current selection path. The
selection path is the set of menu elements from the top-level JMenu on the JMenuBar to the
selected components. For the most part, the manager works behind the scenes, and you never
need to worry about it.
Listening to JMenuItem Events with a MenuDragMouseListener
Like MenuKeyEvent , the MenuDragMouseEvent is a special kind of event used internally by the user
interface classes for JMenu and JMenuItem . As its name implies, the MenuDragMouseEvent is a
special kind of MouseEvent . By monitoring when a mouse is moved within an open menu, the
user interface classes use the listener to maintain the selection path, thus determining the
currently selected menu item. Its definition follows:
public interface MenuDragMouseListener extends EventListener {
public void menuDragMouseDragged(MenuDragMouseEvent e);
public void menuDragMouseEntered(MenuDragMouseEvent e);
public void menuDragMouseExited(MenuDragMouseEvent e);
public void menuDragMouseReleased(MenuDragMouseEvent e);
}
As with the MenuKeyListener , normally you don't listen for this event yourself. If you're
interested in when a menu or submenu is about to be displayed, the better listener to register
is the MenuListener , which can be registered with the JMenu , but not with an individual JMenuItem .
You'll look at this in the next section, which describes JMenu .
The definition of the MenuDragMouseEvent class, the argument to each of the
MenuDragMouseListener methods, is as follows:
public class MenuDragMouseEvent extends MouseEvent {
public MenuDragMouseEvent(Component source, int id, long when, int modifiers,
int x, int y, int clickCount, boolean popupTrigger, MenuElement path[],
MenuSelectionManager mgr);
public MenuSelectionManager getMenuSelectionManager();
public MenuElement[] getPath();
}
Customizing a JMenuItem Look and Feel
As with the JMenuBar , the predefined look and feel types each provide a different JMenuItem
appearance and set of default UIResource values. Figure 6-3 showed the appearance of the
JMenuItem component for the preinstalled set: Motif, Windows, and Ocean.
The available set of UIResource -related properties for a JMenuItem are shown in Table 6-4.
The JMenuItem component offers 20 different properties.