How can I paint in an specific JPanel when more than one in same frame- Java

Question

Updated - this is related with the following link I posted yesterday.

https://stackoverflow.com/questions/15916360/swing-gui-application-in-java-with-multiple-frames

Answer 1

You could...

Use the glass pane...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class TestGlassPane04 {

    public static void main(String[] args) {
        new TestGlassPane04();
    }

    public TestGlassPane04() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }
                
                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new GridLayout(2, 2, 10, 10));
                frame.add(createBox(1));
                frame.add(createBox(2));
                frame.add(createBox(3));
                frame.add(createBox(4));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setGlassPane(new GlassPane());
                frame.getGlassPane().setVisible(true);
                frame.setVisible(true);
            }
        });
    }
    
    protected JLabel createBox(int box) {
        JLabel label = new JLabel("Box " + box);
        label.setBorder(new CompoundBorder(new LineBorder(Color.GRAY), new EmptyBorder(10, 10, 10, 10)));
        return label;
    }
    
    public class GlassPane extends JPanel {
        
        private BufferedImage background;
        
        public GlassPane() {
            setOpaque(false);
            try {
                background = ImageIO.read(getClass().getResource("/sillydash.png"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        
        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }
        
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            if (background != null) {
                int x = (getWidth() - background.getWidth()) / 2;
                int y = (getHeight() - background.getHeight()) / 2;
                g2d.drawImage(background, x, y, this);
            }
            g2d.dispose();
        }
    }
    
}

Take a look at How to use Root Panes for more details...

Or you could...

Use a JXLayer/JLayer to accomplish a more localized version of a glass pane...