Question

I want a JComboBox without a arrow button (done), which has a green background, when enabled and a gray background when disabled (not done). I also use a custom renderer for the drop down list (done)

I checked the source code of BasicComboBoxUI and tried to override some methods, but nothing happens. The dropdown always has a gray/blue background.

Here is a SSCCE with my last attempts. I tried everything I could think of. Please give me a hint, I’m lost.

    import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Rectangle;

import javax.swing.BorderFactory;
import javax.swing.DefaultComboBoxModel;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.plaf.basic.BasicComboBoxUI;

public class DropDownBackground
{
    public static void main(final String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {

            public void run()
            {
                final JComboBox dropdown = new JComboBox(new DefaultComboBoxModel(new String[] { "one", "two", "three" }));
                dropdown.setRenderer(new ComboBoxListCellRenderer());
                dropdown.setUI(new BasicComboBoxUI()
                {
                    @Override
                    public void paint(final Graphics g, final JComponent c)
                    {

                        final Rectangle r = this.rectangleForCurrentValue();
                        this.paintCurrentValueBackground(g, r, true);
                        this.paintCurrentValue(g, r, true);

                    }

                    @Override
                    public void paintCurrentValueBackground(final Graphics g, final Rectangle bounds, final boolean hasFocus)
                    {
                        final Color t = g.getColor();
                        if (this.comboBox.isEnabled())
                            g.setColor(Color.GREEN);
                        else
                            g.setColor(Color.GRAY);
                        g.fillRect(bounds.x, bounds.y, bounds.width, bounds.height);
                        g.setColor(t);
                    }

                    @Override
                    protected JButton createArrowButton()
                    {
                        return new JButton()
                        {
                            @Override
                            public int getWidth()
                            {
                                return 0;
                            }
                        };
                    }
                });
                dropdown.setBackground(Color.GREEN);
                final JPanel p = new JPanel();
                p.add(dropdown);

                final JFrame f = new JFrame();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.getContentPane().add(new JScrollPane(p));
                f.setSize(800, 200);
                f.setLocation(0, 0);

                f.setVisible(true);

            }
        });

    }

    public static class ComboBoxListCellRenderer extends DefaultListCellRenderer
    {
        /**
         * 
         */
        private static final long serialVersionUID = 1L;

        @Override
        public Component getListCellRendererComponent(final JList list, final Object value, final int index, final boolean isSelected, final boolean cellHasFocus)
        {
            this.setToolTipText((String) value);
            if (isSelected)
            {
                this.setBackground(Color.RED);
                this.setForeground(Color.WHITE);
            }
            else
            {
                this.setBackground(Color.WHITE);
                this.setForeground(Color.BLACK);
            }

            this.setText((String) value);
            this.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));

            return this;
        }
    }

}

Answer 1

Since I wanted to have this colors application wide, this was the best approach:

UIManager.put("ComboBox.background", new ColorUIResource(UIManager.getColor("TextField.background")));
UIManager.put("ComboBox.foreground", new ColorUIResource(UIManager.getColor("TextField.foreground")));
UIManager.put("ComboBox.selectionBackground", new ColorUIResource(Color.GREEN));
UIManager.put("ComboBox.selectionForeground", new ColorUIResource(Color.WHITE));

If you want to customize even more (disabled colors etc) this list of UIManager properties might be useful: http://www.rgagnon.com/javadetails/JavaUIDefaults.txt