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javaswingappletawtpaintcomponent

using paintComponent method in JApplet


I have create a program in Java which allows dragging of two oval shapes. Now I want to convert it to a JApplet so I made the class extend JApplet instead of original JPanel. The problem with this is that super.paintComponent(g) does not work as it is no longer a parent class.

I have tried creating a JPanel within the class then referring to this but I get the error: The method paintComponent(Graphics) from the type JComponent is not visible

Any heads up on what I need to do or any help would be much appreciated thanks.

Here is my code.

public class Main extends JPanel 
{
    private static final String TITLE = "Drag me!";
    private static final int W = 640;
    private static final int H = 480;
    private Point origin = new Point(W / 2, H / 2);
    private Point mousePt;
    public Main() {

    this.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
    this.addMouseListener(new MouseAdapter() 
    {
            @Override
            public void mousePressed(MouseEvent e) 
            {
                mousePt = e.getPoint();
                repaint();
            }
        });
    this.addMouseMotionListener(new MouseMotionAdapter() 
    {
            @Override
            public void mouseDragged(MouseEvent e) 
            {
                int dx = e.getX() - mousePt.x;
                int dy = e.getY() - mousePt.y;
                origin.setLocation(origin.x + dx, origin.y + dy);
                mousePt = e.getPoint();
                repaint();
            }
    });
    }

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

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawOval(0, origin.y, getWidth(), origin.y);
        g.drawOval(origin.x, 0, origin.x, getHeight());
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame f = new JFrame(TITLE);
                f.add(new Main());
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.pack();
                f.setLocationRelativeTo(null);
                f.setVisible(true);
            }
        });
    }
}

Solution

  • Instead of modifying your JPanel, keep it and create a new class, your JApplet class:

    public class YourJApplet extends JApplet{
        public void init(){
            final JPanel panel = new YourPanel();
            this.setContentPane(panel);
        }
    }
    

    That's it--now whatever was going on with your panel is now your JApplet.