将Keylistener添加到全屏JWindow

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

public class WindowTest
{
    public static void main(String[] args)
    {

        JFrame frame = new JFrame();
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//      frame.setLocation(-200, 0); // uncomment this line to hide the dummy frame
        frame.setVisible( true );

        JWindow window = new JWindow(); // this doesn\'t work
//      JWindow window = new JWindow(frame); // this works

        window.getContentPane().add( new JTextField(10), BorderLayout.NORTH );
        window.getContentPane().add( new JButton(\"Button\") );
        String[] items = { \"Select Item\", \"Color\", \"Shape\", \"Fruit\" };
        JComboBox mainComboBox = new JComboBox( items );
        window.getContentPane().add( mainComboBox, BorderLayout.SOUTH );

        window.setBounds(50, 50, 200, 200);
        window.setVisible(true);
        window.getRootPane().setBorder(new javax.swing.border.MatteBorder(4, 4, 4, 4, Color.BLUE));
     }
}

JFrame frame = new JFrame();
frame.setUndecorated(true);

myContentPane.setFocusable(true);