Scope problems with 'this' keyword [duplicate]

Question

I am trying to create my own window class which extends JFrame. However, I am having a problem with the action listener for fullScreenBtn. When writing the ActionListener.actionPerformed funcion, I am unable to use the this keyword as it refers to new ActionListener. How do I refer to the instance of MyWindow instead?

public class MyWindow extends JFrame {
    private static GraphicsEnvironment gEnv = GraphicsEnvironment.getLocalGraphicsEnvironment();
    private static GraphicsDevice gDev = gEnv.getDefaultScreenDevice();
    private static JPanel toolbar = new JPanel();
    private static JButton fullScreenBtn = new JButton("Show Full Screen");
    private static boolean isFullScreen = false;

    public MyWindow() {
        toolbar.setLayout(new FlowLayout());
        this.getContentPane().add(toolbar, BorderLayout.PAGE_START);

        fullScreenBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // Toggle full screen window
                this.setUndecorated(!isFullScreen);
                this.setResizable(isFullScreen);
                gDev.setFullScreenWindow(this);

                isFullScreen = !isFullScreen;

                if (isFullScreen) {
                    fullScreenBtn.setText("Show Windowed");
                } else {
                    fullScreenBtn.setText("Show Full Screen");
                }
            }
        });

        this.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent windowEvent) {
                this.dispose();
                System.exit(0);
            }
        });
    }
}

Answer 1

In inner classes you will need to prepend your use of this with the class name of the outer class if you need to obtain a reference to the outer class: For example, use

MyWindow.this.setUndecorated(...)` 
//  etc...

As an aside, you really don't want to extend JFrame here, and in most situations.

Also, the ancestor Window that holds the JButton can be obtained in other ways such as via SwingUtilities.getWindowAncestor(theButton). i.e.,

        public void actionPerformed(ActionEvent e) {
            Object source = e.getSource();
            if (source instanceof JButton) {
              JButton button = (button) source;
              Window ancestorWin = SwingUtilities.getAncestorWindow(button);
              ancestorWin.setUndecorated(!isFullScreen);
              ancestorWin.setResizable(isFullScreen);
              // etc...

Or if you know most definitely that the ancestor window is a JFrame:

        public void actionPerformed(ActionEvent e) {
            Object source = e.getSource();
            if (source instanceof JButton) {
              JButton button = (button) source;

              JFrame ancestorWin = (JFrame) SwingUtilities.getAncestorWindow(button);
              ancestorWin.setUndecorated(!isFullScreen);
              ancestorWin.setResizable(isFullScreen);
              // etc...

Answer 2

This is the syntax of accessing the enclosing-class's instance from an inner-class or an anonymous-class:

OuterClass.this.foo();