Hello,

I have a window that has two layers: a static background and a foreground that contains moving objects. My idea is to draw the background just once (because it's not going to change), so I make the changing panel transparent and add it on top of the static background. Here is the code for this:

public static void main(String[] args) {
    JPanel changingPanel = new JPanel() {

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.fillRect(100, 100, 100, 100);
        }
    };
    changingPanel.setOpaque(false);

    JPanel staticPanel = new JPanel();
    staticPanel.setBackground(Color.BLUE);
    staticPanel.setLayout(new BorderLayout());
    staticPanel.add(changingPanel);

    JFrame frame = new JFrame();
    frame.add(staticPanel);
    frame.setSize(800, 600);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
}

This piece of code gives me the correct image I want, but every time I repaint changingPanel, staticPanel gets repainted as well (which is obviously against the whole idea of painting the static panel just once). Can somebody show me what's wrong?

FYI I am using the javax.swing.Timer to recalculate and repaint the changing panel 24 times every second.