Re: Detect when menu is chosen in JMenu

From:
"John B. Matthews" <nospam@nospam.invalid>
Newsgroups:
comp.lang.java.gui
Date:
Tue, 09 Sep 2008 19:51:38 -0400
Message-ID:
<nospam-326D2A.19513809092008@news.motzarella.org>
In article
<ed522ffd-eb04-440b-9a67-c250d3df8f8a@f36g2000hsa.googlegroups.com>,
 izittm@gmail.com wrote:

Sure, should have done that at the beginning. Here's what I tried:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;

public class MenuPrb {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        JMenuBar jmb = new JMenuBar();
        frame.add(jmb);
        JMenu menu1 = new JMenu("menu1");
        jmb.add(menu1);

        JMenu menu2 = new JMenu("menu2");
        menu1.add(menu2);
        menu2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.out.println("menu2: actionPerformed");
            }
        });
        menu2.addMouseListener(new MouseAdapter() {
            public void mouseClicked(MouseEvent e) {
                System.out.println("menu2: mouseClicked");
            }
        });
        menu2.addKeyListener(new KeyListener() {
            public void keyPressed(KeyEvent e) {
                System.out.println("menu2: keyPressed");
            }
            public void keyReleased(KeyEvent e) {
                System.out.println("menu2: keyReleased");
            }
            public void keyTyped(KeyEvent e) {
                System.out.println("menu2: keyTyped");
            }
        });

        for(int i = 0; i < 10; i++) {
            JMenuItem mi = new JMenuItem("menu item " + i);
            menu2.add(mi);
            mi.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    System.out.println("mi: actionPerformed");
                }
            });
        }

        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

If you click on any of the menu items, it works. If you click on
menu2, it doesn't. That is what I would like to achieve - get clicks
from menu2. It can be done by menu2.addMouseListener(...) as above,
but that won't catch keyboard activation. menu2.addKeyListener doesn't
work also, as you can see - none of the keys pressed over menu2
trigger either action or key event handlers. Enter works on menu items
by triggering action events (in my opinion correct behavior).


I see. Normally, activating a menu item containing a submenu serves only
to display the submenu. Indeed, the left and right arrow keys hide and
show the submenu, as expected. You want to see that display event: you
can see the corresponding mouse event in a mouse listener, but the
keyboard event is not getting through. You might see if a FocusListener
will report the event.

Notice that in both links you provided (I've already read the first
one) they never set any listeners on JMenu, only on JMenuItem. Maybe
this is not what they had in mind, but I consider this quite oddly
designed in that case. After all, JMenu is a descendant of
AbstractButton. I'd expect a button to be clickable... Clickable in
the same way as other buttons - by mouse & keyboard, yielding
actionPerformed events.


I'm curious what meaning to attach to activating menu2, other than to
display the submenu.

--
John B. Matthews
trashgod at gmail dot com
home dot woh dot rr dot com slash jbmatthews

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