Get location of multiple drawings in paintComponent

Question

I would need to get the location coordinates of all the drawings I'm creating in the paintComponent method. How can I do this?

Notice that I use the timer to perform some animations so the coordinates change at every tick of the timer.

public class TestPane extends JPanel {

    private int x = 0;
    private int y = 100;
    private int radius = 20;
    private int xDelta = 2;

    public TestPane() {
        Timer timer = new Timer(10, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                x += xDelta;
                if (x + (radius * 2) > getWidth()) {
                    x = getWidth() - (radius * 2);
                    xDelta *= -1;


                } else if (x < 0) {
                    x = 0;
                    xDelta *= -1;
                }
                label.setText(x+" "+y);
                repaint();
            }
        });
        timer.start();
    }

More code...

 protected void paintComponent(Graphics g) {
            Random random = new Random();
            super.paintComponent(g);
            g.setColor(Color.ORANGE);
            g.fillOval(random.nextInt(500), random.nextInt(500) - radius, radius * 2, radius * 2);

            g.setColor(Color.BLUE);
            g.fillOval(y, x - radius, radius * 2, radius * 2);
//            label.setText(label.getText()+ x+" "+y); ;
            g.setColor(Color.RED);
            g.fillOval(x, y - radius, radius * 2, radius * 2);
//            label.setText(label.getText()+ x+" "+y);
        }

Answer 1

Your program should maintain a List<Node> as a class level attribute. Each instance of Node should contain the geometry required to render each element in your program.

class Node {
    private Point p;
    private int r;
    …
}

In your ActionListener, update the fields of each Node in the List. When a repaint() occurs, the new positions will be waiting for paintComponent() to render.

@Override
public void paintComponent(Graphics g) {
    …
    for (Node n : nodes) {
        // draw each node
    }

A complete example, named GraphPanel, is cited here.