Switch JFrame setUndecorated On and Off, help

Question

i need to make a frame so that if the user hits f4 the frame decorations
disappear.
If i open the frame with setundecorated(true) the frame works fine.
The same with the default setUndec(false).
However it is unable to switch from one to the other.
A jframe can only be undecorated when it is undispalayble.
How do i make it undisplayable but displayed?
If i call removeNotify() (the only way i know to make the frame
undisplayable - otherwise setundec throws an error) the frame closes.
Anyone have any suggestions? this is really important! thanks alot!

Answer 1

Here's a slight modification. Notice I had to re-map action and keyStroke.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class UndecoratedFrameTest extends JFrame {
    private boolean unDecorated = false;
    private DecorateAction action;
    private JPanel mainPanel;
    public UndecoratedFrameTest() {
        action = new DecorateAction("Toggle");
        buildGUI();
    private void buildGUI() {
        mainPanel = (JPanel) getContentPane();
        mainPanel.setLayout(new BorderLayout());
        JPanel centerPanel = new JPanel();
        centerPanel.add(new JLabel("Center"));
        mainPanel.add(centerPanel, BorderLayout.CENTER);
        setUndecorated(unDecorated);
        JButton decButton = new JButton(action);
        mainPanel.add(decButton, BorderLayout.SOUTH);
        mainPanel.getActionMap().put("toggle", action);
        mainPanel.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_F4, 0), "toggle");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setLocationRelativeTo(null);
    private void toggleDecoration() {
        dispose();
        setUndecorated(!unDecorated);
        mainPanel.getActionMap().put("toggle", action);
        mainPanel.getInputMap().put(KeyStroke.getKeyStroke(KeyEvent.VK_F4, 0), "toggle");
        setVisible(true);
        unDecorated = !unDecorated;
    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            public void run() {
                UndecoratedFrameTest undecoratedFrameTest = new UndecoratedFrameTest();
                undecoratedFrameTest.setVisible(true);
        SwingUtilities.invokeLater(runnable);
    private class DecorateAction extends AbstractAction {
        public DecorateAction(String name) {
            super(name);
        public void actionPerformed(ActionEvent e) {
            toggleDecoration();
}Cheers
DB