Question

When I code a popup menu, I can check the mouse event and then
before calling show() prepare the menu.

Now I want a similar functionality for drop down menus, that
live in the menu bar. For example I have the following menu
bar layout:

Menu 1
   MenuItem 1.1
      MenuItem 1.1.1
      MenuItem 1.1.2
      ..
      MenuItem 1.1.n
Menu 2

Basically I want to generate the list MenuItem 1.1.1, MenuItem 1.1.2,
…, MenuItem 1.1.n dynamically when the drop down menu is invoked and
before it is shown.

How could I do this in Java/Swing? Is there a call back that covers both
L&F specific keyboard/mouse invokations of the menu bar?

Best Regards

Answer 1

You need to use a javax.swing.JMenuBar instead of a java.​awt.MenuBar.
These MenuBars can add javax.​swing.JMenus which have a addMenuListener(MenuListener l) method.

In this MenuListener you can dynamically add and delete the menus.

@Override
public void menuSelected(MenuEvent e) {
    // Put your logic here
    JMenu dynamicMenu = (JMenu) e.getSource();
    dynamicMenu.add(new JMenuItem("MenuItem 1.1.1"));
}

@Override
public void menuDeselected(MenuEvent e) {
    // Remove all MenuItems
    JMenu dynamicMenu = (JMenu) e.getSource();
    dynamicMenu.removeAll();
}

@Override
public void menuCanceled(MenuEvent e) {
    // Remove all MenuItems
    JMenu dynamicMenu = (JMenu) e.getSource();
    dynamicMenu.removeAll();
}

To add the JMenuBar to a JFrame use the setJMenuBar(JMenuBar menubar) method.