Make a custom JScrollBar using an image

Question

So I use Java Swing to build the UI for my app and use custom images to replace the ugly Java ones, the custom images have a style and are very easy to integrate into Java S

Answer 1

Where the buttons were remains a small grey area, but I don't know how to remove this.

Here's a variation of @halex's example that removes the buttons and lets the graphics context do the scaling. I added a faux image to make the example self-contained.

import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.plaf.metal.MetalScrollBarUI;

/** @see http://stackoverflow.com/a/12270067/230513 */
public class CustomScrollbarUIExample {

    public static void main(String[] args) {
        JScrollPane before = makeExamplePane();
        JScrollPane after = makeExamplePane();
        JScrollBar sb = after.getVerticalScrollBar();
        sb.setUI(new MyScrollbarUI());
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLayout(new GridLayout(0,1));
        f.add(before);
        f.add(after);
        f.pack();
        f.setSize(320, 240);
        f.setVisible(true);
    }

    private static JScrollPane makeExamplePane() {
        JTextArea text = new JTextArea(16, 16);
        text.append("Lorem ipsum dolor sit amet…");
        JScrollPane scroll = new JScrollPane(text);
        return scroll;
    }

    static class MyScrollbarUI extends MetalScrollBarUI {

        private Image imageThumb, imageTrack;
        private JButton b = new JButton() {

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(0, 0);
            }

        };

        MyScrollbarUI() {
            imageThumb = FauxImage.create(32, 32, Color.blue.darker());
            imageTrack = FauxImage.create(32, 32, Color.lightGray);
        }

        @Override
        protected void paintThumb(Graphics g, JComponent c, Rectangle r) {
            g.setColor(Color.blue);
            ((Graphics2D) g).drawImage(imageThumb,
                r.x, r.y, r.width, r.height, null);
        }

        @Override
        protected void paintTrack(Graphics g, JComponent c, Rectangle r) {
            ((Graphics2D) g).drawImage(imageTrack,
                r.x, r.y, r.width, r.height, null);
        }

        @Override
        protected JButton createDecreaseButton(int orientation) {
            return b;
        }

        @Override
        protected JButton createIncreaseButton(int orientation) {
            return b;
        }
    }

    private static class FauxImage {

        static public Image create(int w, int h, Color c) {
            BufferedImage bi = new BufferedImage(
                w, h, BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2d = bi.createGraphics();
            g2d.setPaint(c);
            g2d.fillRect(0, 0, w, h);
            g2d.dispose();
            return bi;
        }
    }
}