Question

I was wondering if there was a function like void draw() which Processing programming language uses that gets called every frame. Or even just a function that loops infinitely when it gets called but only runs through it every time there is a new frame. I heard of something called a runnable in java how do i go about using this? also is there a better way then having a runnable with a delay like a function that is hardcoded to run every frame. Oh and also what is the function call that will allow me to see how much time (in milliseconds preferably) since the application has started running that way i can make my runnables / frame calls much more precise so that the game runs about the same speed on every computer regardless of the frame rate.

Answer 1

Perhaps you need something like this

import java.awt.Graphics;
import java.awt.Point;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

public class Repainter extends JPanel {
    private Point topLeft;
    private int increamentX = 5;

    public Repainter() {
        topLeft = new Point(100, 100);
    }

    public void move() {
        topLeft.x += increamentX;
        if (topLeft.x >= 200 || topLeft.x <= 100) {
            increamentX = -increamentX;
        }

        repaint();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawRect(topLeft.x, topLeft.y, 100, 100);
    }

    public void startAnimation() {
        SwingWorker<Object, Object> sw = new SwingWorker<Object, Object>() {
            @Override
            protected Object doInBackground() throws Exception {
                while (true) {
                    move();
                    Thread.sleep(100);
                }
            }
        };

        sw.execute();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame frame = new JFrame("Repaint Demo");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setSize(400, 400);

                Repainter repainter = new Repainter();

                frame.add(repainter);

                repainter.startAnimation();
                frame.setVisible(true);
            }
        });
    }
}