Java Swing - Creating JSlider and Listening to ChangeEvent

Following is a basic JSlider example. We will use JSlider to change the radius of a circle. We will also add ChangeListener for listening to value changes of the slider.

Example

public class JSliderExampleMain {
    public static void main(String[] args) {
        JFrame frame = createFrame();
        JSlider slider = createSlider();
        CirclePanel circlePanel = new CirclePanel();
        slider.addChangeListener(changeEvent -> {
            JSlider s = (JSlider) changeEvent.getSource();
            circlePanel.setRadius(s.getValue());
        });
        frame.add(slider, BorderLayout.NORTH);
        frame.add(circlePanel);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private static JSlider createSlider() {
        JSlider slider = new JSlider();
        slider.setMaximum(100);
        slider.setValue(50);
        slider.setMajorTickSpacing(10);
        slider.setMinorTickSpacing(5);
        slider.setPaintTicks(true);
        slider.setPaintLabels(true);
        return slider;
    }

    private static JFrame createFrame() {
        JFrame frame = new JFrame("JSlider Basic example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(new Dimension(400, 300));
        return frame;
    }
}

public class CirclePanel extends JPanel {
    private int radius = 50;

    public CirclePanel() {
        setBorder(BorderFactory.createLineBorder(Color.GRAY, 3));
    }

    public void setRadius(int radius) {
        this.radius = radius;
        repaint();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(Color.pink);
        g.fillOval(getWidth() / 2 - radius,
                getHeight() / 2 - radius,
                2 * radius, 2 * radius);
    }
}

Output

Example Project

Dependencies and Technologies Used:

• JDK 1.8
• Maven 3.3.9