Java – JPanel Animated Background

animationbackgroundjavajpanelswing

This is a really general question, but how should I add an animated background for a JPanel. I want the background to be behind all the panel's components and graphics. Right now, I have two separate classes (one for the main panel and the other for the background). The background class uses repaint() to animate a grid moving across the screen. I've tried to make the main panel background transparent, but that hasn't gotten me anywhere.

Even more info:
My main panel is part of a CardLayout and it has many different classes in it. So when I'm adding my main panel to my main frame, I'm doing frame.getContentPane().add(cards, BorderLayout.CENTER)

cards is a JPanel which acts as a container for the mainpanel and all the panels inside main panel.

Can anybody help me out in getting a panel animated background?

Best Answer

You can use Toolkit.getImage() to load animated image and then draw the image in container's paintComponent. Make sure the ImageObserver is set (not null) in order to update animation frames properly. For details how image is loaded, observed and updated see How Images are Loaded appendix in Java AWT Reference.

Here is a simple example: 

import java.awt.*;
import javax.swing.*;
import java.net.URL;

class AnimatedPanelDemo {
    static class ImagePanel extends JPanel {
        private Image image;
        ImagePanel(Image image) {
            this.image = image;
        }
        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawImage(image,0,0,getWidth(),getHeight(),this);
        }
    }

    private static void createAndShowUI() {
        try {
            JFrame frame = new JFrame("Image");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setLocationRelativeTo(null);

            Image image = Toolkit.getDefaultToolkit().getImage(new URL(
                    "http://duke.kenai.com/iconSized/duke.running.gif"));

            ImagePanel imagePanel = new ImagePanel(image);

            imagePanel.add(new JLabel("Some label"));
            frame.add(imagePanel);
            frame.setSize(100, 100);
            frame.setVisible(true);
        } 
        catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowUI();
            }
        });
    }
}
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