Make jtoolbar transparent

Question

I have a jPanel with background and I want to add a JToolbar on it.
My problem is when I add JToolbar its default background is bothering and I set it's opaque to false but has no effect.
I want to remove it's default background and make it transparent.
I read the following article but no help:
JToolbar background image
Here is my code:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;

import javax.swing.Action;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JToolBar;

public class Toolbar extends JToolBar {

    private JButton manage;
    private JButton add;
    private JButton search;
    private JButton exit;

    public Toolbar() {
        super();

        manage = new JButton();
        add = new JButton();
        search = new JButton();
        exit = new JButton();

        ImageIcon icon = new ImageIcon("pics/Add-01.png");
        Image img = icon.getImage();
        Image newImage = img.getScaledInstance(80, 80, Image.SCALE_SMOOTH);
        add.setIcon(new ImageIcon(newImage));

        setOpaque(false);

        setBackground(Color.RED);

        add(add);
        add(search);
        add(manage);
        add(exit);

    }

}

Thank you for your support.
Not working code:

public class Toolbar extends JToolBar {

    public Toolbar() {
        setBackground(Color.RED);
        setOpaque(false);
        add(new JButton("add"));
    }

    protected void addImpl(Component comp, Object constraints, int index) {
        super.addImpl(comp, constraints, index);
        if (comp instanceof JButton) {
            ((JButton) comp).setContentAreaFilled(false);
        }
    }

}

Answer 1

Basically, the buttons are still "filling" their backgrounds. You can instruct them to not paint their content (background) through JButton#setContentAreaFilled

This example sets the background color of the JToolBar to red, so you can see that the buttons are now transparent. To make the tool bar transparent, simply add setOpaque(false) in the constructor

public class CustomToolBar extends JToolBar {

    public CustomToolBar() {
        setBackground(Color.RED);
    }

    protected void addImpl(Component comp, Object constraints, int index) {
        super.addImpl(comp, constraints, index);
        if (comp instanceof JButton) {
            ((JButton) comp).setContentAreaFilled(false);
        }
    }

}

Extended example....

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JToolBar;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JButton manage = new JButton("Manage");
                JButton add = new JButton("Add");
                JButton search = new JButton("Search");
                JButton exit = new JButton("Exit");
                CustomToolBar tb = new CustomToolBar();
                tb.add(manage);
                tb.add(add);
                tb.add(search);
                tb.add(exit);

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setContentPane(new TestPane());
                frame.add(tb, BorderLayout.NORTH);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage bgImg;

        public TestPane() {
            setLayout(new BorderLayout());
            try {
                bgImg = ImageIO.read(new File("..."));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return bgImg == null ? new Dimension(200, 200) : new Dimension(bgImg.getWidth(), bgImg.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (bgImg != null) {
                Graphics2D g2d = (Graphics2D) g.create();
                int x = (getWidth() - bgImg.getWidth()) / 2;
                int y = (getHeight() - bgImg.getHeight()) / 2;
                g2d.drawImage(bgImg, x, y, this);
                g2d.dispose();
            }
        }

    }

    public class CustomToolBar extends JToolBar {

        public CustomToolBar() {
            setBorder(new LineBorder(Color.BLACK, 2));
            setOpaque(false);
        }

        @Override
        protected void addImpl(Component comp, Object constraints, int index) {
            super.addImpl(comp, constraints, index);
            if (comp instanceof JButton) {
                ((JButton) comp).setContentAreaFilled(false);
            }
        }

    }

}