Difference between LookAndFeel behavior

I created a JPopupmenu and i added a JTextField. When I am using metal or nimbus everything is alright. The problem is when I switch LookAndFeel to Windows. I can not press right ALT, because if I press this key, JPopupmenu will hide.

Can I use right ALT to write national signs in Windows LookAndFeel?

import javax.swing.*;
import java.awt.event.*;

public class Popup extends JFrame {

    JPopupMenu popup;
    JPanel panel;
    JTextField field;

    public Popup(){
        setSize(500,400);
        try {
            //UIManager.setLookAndFeel("javax.swing.plaf.nimbus.NimbusLookAndFeel");
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } catch (ClassNotFoundException | InstantiationException
                | IllegalAccessException | UnsupportedLookAndFeelException e1) {
            e1.printStackTrace();
        }
        SwingUtilities.updateComponentTreeUI(this);

        popup = new JPopupMenu();
        field = new JTextField(10);
        popup.add(field);
        JButton button = new JButton("Options");
        button.addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                popup.show(e.getComponent(), e.getX(), e.getY());
            }
        });        

        panel = new JPanel();
        panel.add(button);
        add(panel);
    }

    public static void main(String[] args){
        Popup pop = new Popup();
        pop.setVisible(true);
    }

}

JPopupMenu has a very specific set of operation requirements, and yes, they do change between look and feels, that's kind of the point.

What you could do is create you own popup using an undecorated JFrame. The trick here is to mimic as much of the popup as need, for example, auto closer when another component gains focus, the ability to dismiss the popup with the escape key...etc...

This is just a quick example to provide a proof of concept, I'd personally also add a key binding for the escape key, some kind of listener interface to allow the search pane to request that the popup be dismissed and the ability to auto focus some component when the window was made visible, but that's just me...

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowFocusListener;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestPopup {

    public static void main(String[] args) {
        new TestPopup();
    }

    public TestPopup() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JButton show;

        public TestPane() {
            setLayout(new GridBagLayout());
            show = new JButton("...");
            show.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    PopupWindow window = new PopupWindow();
                    window.show(show, 0, show.getHeight());
                }
            });
            add(show);
        }

    }

    public class SearchPane extends JPanel {

        private JList list;
        private JTextField search;

        public SearchPane() {
            setLayout(new BorderLayout());
            list = new JList();
            list.setPrototypeCellValue("This is just a test");
            list.setVisibleRowCount(20);
            search = new JTextField(10);
            add(new JScrollPane(list));
            add(search, BorderLayout.SOUTH);
        }

    }

    public class PopupWindow extends JFrame {

        private SearchPane searchPane;

        public PopupWindow() {
            setUndecorated(true);
            setDefaultCloseOperation(DISPOSE_ON_CLOSE);
            addWindowFocusListener(new WindowFocusListener() {

                @Override
                public void windowGainedFocus(WindowEvent e) {
                }

                @Override
                public void windowLostFocus(WindowEvent e) {
                    dispose();
                }
            });
            searchPane = new SearchPane();
            add(searchPane);
            pack();
        }

        public void show(JComponent parent, int x, int y) {
            Point point = new Point(x, y);
            SwingUtilities.convertPointToScreen(point, parent);
            setLocation(point);
            setVisible(true);
        }

    }

}