Custom UI painting problem

Question

I have a JInternalFrame that I am applying a custom UI to. The UI paints the component, but when I add a JPanel to the JInternalFrame it doesn't show up. I think the UI is paining over the whole component, but how do I paint the UI THEN paint the components?

But if anyone has a better way of doing this, please let me know! Thanks!

public class ClassInternalFrame extends JInternalFrame {
    public static Color currentColor;
    public static final Color CLASS_TYPE = new Color(148, 227, 251);

    public ClassInternalFrame(String title, Color classType) {
        super(title, true, true, false, true);
        currentColor = classType;
        super.setUI(new ClassFrameUI());

        Container pane = super.getContentPane();
        pane.setLayout(new BorderLayout());

        JPanel titlePanel = new JPanel();
        titlePanel.setPreferredSize(new Dimension(0, 20));
        pane.add(titlePanel, BorderLayout.NORTH);

        titlePanel.setBorder(new MatteBorder(1, 1, 1, 1, Color.yellow));
    }

}

class ClassFrameUI extends InternalFrameUI {
    private final static ClassFrameUI frmUI = new ClassFrameUI();

    public static ComponentUI createUI(JComponent c) {
        return frmUI;
    }

    @Override
    public void paint(Graphics g, JComponent c)
    {
        Graphics2D g2d = (Graphics2D) g;

        g2d.setColor(Color.LIGHT_GRAY);
        g2d.fillRect(0, 0, c.getWidth(), c.getHeight());

        g2d.setColor(ClassInternalFrame.currentColor);
        g2d.fillRect(0, 0, c.getWidth(), 20);

        g2d.setColor(Color.DARK_GRAY);
        g2d.setStroke(new BasicStroke(1, BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL, 0, new float[] { 1, 0 }, 0));
        g2d.drawRect(0, 0, c.getWidth()-1, c.getHeight()-1);
        g2d.drawLine(0, 20, c.getWidth(), 20);


    }
}

Answer 1

The problem is not that you're painting over anything, but that InternalFrameUI does absolutely nothing (if it did, you would also need to call super.paint(g, c);). Normally, painting of the components is done by a subclass such as BasicInternalFrameUI. It looks like you're trying to paint a custom title bar, a task that BasicInternalFrameUI delegates to BasicInternalFrameTitleBar.