SliderUI.java

import java.awt.*;
import javax.swing.*;
import java.awt.geom.*;
import javax.swing.plaf.basic.*;

public class SliderUI
{
    public static class CustomSliderUI extends BasicSliderUI
    {

        private static final int TRACK_HEIGHT = 8;
        private static final int TRACK_WIDTH = 8;
        private static final int TRACK_ARC = 5;
        private static final Dimension THUMB_SIZE = new Dimension(20, 20);
        private final RoundRectangle2D.Float trackShape = new RoundRectangle2D.Float();
    
        public CustomSliderUI(final JSlider b)
        {
            super(b);
        }
    
        @Override
        protected void calculateTrackRect()
        {
            super.calculateTrackRect();
            if (isHorizontal())
            {
                trackRect.y = trackRect.y + (trackRect.height - TRACK_HEIGHT) / 2;
                trackRect.height = TRACK_HEIGHT;
            }
            else
            {
                trackRect.x = trackRect.x + (trackRect.width - TRACK_WIDTH) / 2;
                trackRect.width = TRACK_WIDTH;
            }
            trackShape.setRoundRect(trackRect.x, trackRect.y, trackRect.width, trackRect.height, TRACK_ARC, TRACK_ARC);
        }
    
        @Override
        protected void calculateThumbLocation()
        {
            super.calculateThumbLocation();
            if (isHorizontal())
            {
                thumbRect.y = trackRect.y + (trackRect.height - thumbRect.height) / 2;
            }
            else
            {
                thumbRect.x = trackRect.x + (trackRect.width - thumbRect.width) / 2;
            }
        }
    
        @Override
        protected Dimension getThumbSize()
        {
            return THUMB_SIZE;
        }
    
        private boolean isHorizontal()
        {
            return slider.getOrientation() == JSlider.HORIZONTAL;
        }
    
        @Override
        public void paint(final Graphics g, final JComponent c)
        {
            ((Graphics2D) g).setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            super.paint(g, c);
        }
    
        @Override
        public void paintTrack(final Graphics g)
        {
            Graphics2D g2 = (Graphics2D) g;
            Shape clip = g2.getClip();
    
            boolean horizontal = isHorizontal();
            boolean inverted = slider.getInverted();
    
            // Paint shadow.
            g2.setColor(new Color(170, 170 ,170));
            g2.fill(trackShape);
    
            // Paint track background.
            g2.setColor(new Color(200, 200 ,200));
            g2.setClip(trackShape);
            trackShape.y += 1;
            g2.fill(trackShape);
            trackShape.y = trackRect.y;
    
            g2.setClip(clip);
    
            // Paint selected track.
            if (horizontal)
            {
                boolean ltr = slider.getComponentOrientation().isLeftToRight();
                if (ltr) inverted = !inverted;
                int thumbPos = thumbRect.x + thumbRect.width / 2;
                if (inverted)
                    g2.clipRect(0, 0, thumbPos, slider.getHeight());
                else
                    g2.clipRect(thumbPos, 0, slider.getWidth() - thumbPos, slider.getHeight());
            }
            else
            {
                int thumbPos = thumbRect.y + thumbRect.height / 2;
                if (inverted)
                    g2.clipRect(0, 0, slider.getHeight(), thumbPos);
                else
                    g2.clipRect(0, thumbPos, slider.getWidth(), slider.getHeight() - thumbPos);
            }
            g2.setColor(Color.ORANGE);
            g2.fill(trackShape);
            g2.setClip(clip);
        }
    
        @Override
        public void paintThumb(final Graphics g)
        {
            g.setColor(Color.WHITE);
            g.fillOval(thumbRect.x, thumbRect.y + 2, 15, 15);
        }
    
        @Override
        public void paintFocus(final Graphics g) {}
    }
}