Problem with multiple transparent JPanels

Question

Hi,
I'm currently trying to implement some kind of message box that can fade in and out. This message box is a subclass of JComponent, the message it contains can be an arbitrary Swing-Component.
The message container and the message itself have the same background color. When fading, the (partly transparent) colors of the of the container and the message are added, which I do not want.
Here are two images to illustrate my problem:
What I have: http://www.inf.tu-dresden.de/~ab023578/javaforum/reality.gif
What I want: http://www.inf.tu-dresden.de/~ab023578/javaforum/wish.gif
Here is the code:
import java.awt.*;
import javax.swing.*;
public class Main {
    static float transparency = 0f;
    public static void main(String[] args) {
        JPanel jpBack = new JPanel() {
            protected void paintComponent(Graphics g) {
                Graphics2D g2d = (Graphics2D)g;
                g2d.clearRect(0, 0, getWidth(), getHeight());
                g2d.setColor(getBackground());
                AlphaComposite alpha = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, transparency);
                g2d.setComposite(alpha);
                g2d.fillRect(0, 0, getWidth(), getHeight());
        jpBack.setBackground(Color.WHITE);
        jpBack.setLayout(null);
        JPanel jpContainer = new JPanel();
        jpContainer.setBackground(Color.RED);
        jpContainer.setLayout(null);
        JPanel jpMessage = new JPanel();
        jpMessage.setBackground(Color.RED);
        JLabel jlMessage = new JLabel("MESSAGE");
        jpBack.add(jpContainer);
        jpContainer.add(jpMessage);
        jpMessage.add(jlMessage);
        jpContainer.setBounds(10, 10, 120, 100);
        jpMessage.setBounds(10, 10, 100, 50);
        JFrame frame = new JFrame();
        frame.setBounds(0, 0, 150, 150);
        frame.setBackground(Color.WHITE);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(jpBack);
        frame.setVisible(true);
        for (double a = 0; true; a += 0.01D) {
            try {
                Thread.sleep(10);
            catch (InterruptedException e) {}
            transparency = (float)Math.abs(Math.sin(a));
            jpBack.repaint();
}I understand that the Porter-Duff-Rule SRC_OVER causes the container to be drawn over the message (or vice versa) and both of them over the background. I think what I need is a way to handle the whole jpContainer-Panel and all its subcomponents as a single source image. Is that possible?

Answer 1

Thank you for your answer, Sarcommand. Unfortunately the test program I provided is a bit too simple as your solution works here but not for my original problem. :|
Let me explain what I want to achieve and why.
I'm writing a tool for algorithm visualisation. Currently I am dealing with a parsing algorithm (having compontents such as an automaton with an input tape, output tape and a stack). Those components (containers) can contain multiple JComponents (GraphicalObjects), which display a BufferedImage that can be altered during the animation.
I want to create my message windows the same way. A container that contains GraphicalObjects (or, if necessary, any other Swing component). One GraphicalObject has a very limited field of responsibility: mereley displaying its information.
Aligning the GraphicalObject is one of the container's responsibilities.
What I'm currently trying to do is to put my GraphicalMessage into the center of a container, leaving an offset on the left/right/upper/lower side. This is why I need the same background color for both the GraphicalMessage and the MessageContainer, I don't want the user to see that there are actually two JComponents on top of each other.
While I could use another approach for text messages I prefer this one as I would be able to fade arbitrary Containers and their GraphicalObjects .
Here is the code:
import java.awt.*;
import javax.swing.*;
import java.awt.image.BufferedImage;
public class Main {
    static float transparency = 0f;
    public static void main(String[] args) {
        JPanel jpBack = new JPanel() {
            protected void paintComponent(Graphics g) {
                Graphics2D g2d = (Graphics2D)g;
                g2d.clearRect(0, 0, getWidth(), getHeight());
                g2d.setColor(getBackground());
                AlphaComposite alpha = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, transparency);
                g2d.setComposite(alpha);
                g2d.fillRect(0, 0, getWidth(), getHeight());
                super.paintComponent(g);
        jpBack.setBackground(Color.WHITE);
        jpBack.setLayout(null);
        JPanel jpContainer = new JPanel();
        jpContainer.setBackground(Color.RED);
        jpContainer.setLayout(null);
        GraphicalMessage msg = new GraphicalMessage();
        jpBack.add(jpContainer);
        jpContainer.add(msg);
        jpContainer.setBounds(10, 10, 120, 100);
        msg.setBounds(10, 10, 160, 60);
        JFrame frame = new JFrame();
        frame.setBounds(0, 0, 150, 150);
        frame.setBackground(Color.WHITE);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(jpBack);
        frame.setVisible(true);
        float stepSize = 0.01f;
        float step = stepSize;
        for (float a = 0; true; a += step) {
            try {
                Thread.sleep(10);
            catch (InterruptedException e) {}
            if (a >= 1) {
                step = -stepSize;
                a -= stepSize;
            if (a <= 0) {
                step = stepSize;
                a += stepSize;
                msg.updateInternalContent();
                msg.redraw();
            transparency = a;
            jpBack.repaint();
class GraphicalMessage extends JComponent {
    private String text;
    private Graphics2D ig2d;
    private BufferedImage image;
    public GraphicalMessage() {
        setLayout(null);
        image = new BufferedImage(100, 50, BufferedImage.TYPE_INT_ARGB);
        ig2d = image.createGraphics();
        ig2d.setColor(Color.BLACK);
        ig2d.setBackground(Color.RED);
        ig2d.setFont(new Font("Courier New", Font.BOLD, 20));
        updateInternalContent();
        redraw();
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D)g;
        g2d.drawImage(image, 0, 0, null);
    public void redraw() {
        ig2d.clearRect(0, 0, image.getWidth(), image.getHeight());
        ig2d.drawString(text, 0, 20);
    public void updateInternalContent() {
        text = String.valueOf((int)(Math.random() * 10000));
}A possibility to erase the text from the BufferedImage without having to draw a rectangle would help me as well.