Randomly moving images on a JPanel

Question

I am using a BufferedImage to display two images on my JPanel. However, I want the images move in random directions when a button is clicked and should only stop when another button is pressed.

How do I make my images move randomly on the panel?

This is part of my code:

 private void getImages() {
    try {
         frogImage = ImageIO.read(new File ("C:\\OOP\\CyberPet\\src\\img\\frog.gif"));
         flyImage = ImageIO.read(new File ("C:\\OOP\\CyberPet\\src\\img\\fly.gif"));

         g = panel.getGraphics();

         g.drawImage(frogImage, 500, 25, 40, 40, null); //set position and size of the image
         g.drawImage(flyImage, 40, 40, 10, 10, null); //set position and size of the image
    } catch (IOException e) {
    }
}

public void actionPerformed(ActionEvent event) {
    getImages();
    if (event.getSource() == makeButton){  

         responseArea.setText(enterField.getText());
      }
      else if(event.getSource() == hungryButton){
      }
      else if(event.getSource() == resetButton){        
    }
}

public void draw()
{
}
}

Answer 1

You can always check this example for inspiration.

Basically, it uses a javax.swing.Timer to pace the animation. Whenever an animal reaches an edge of the frame, it will reverse its direction to go in reverse. The directions and speed are randomly computed, adjust these to your needs:

import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Random;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.UnsupportedLookAndFeelException;

public class TestAnimationFlyAndFrog {
    private static final int NB_OF_IMAGES_PER_SECOND = 50;
    private static final int WIDTH = 800;
    private static final int HEIGHT = 600;
    private Random random = new Random();

    private double dxFrog;
    private double dyFrog;

    private double xFrog = WIDTH / 2;
    private double yFrog = HEIGHT / 2;

    private double dxFly;
    private double dyFly;

    private double xFly = WIDTH / 2;
    private double yFly = HEIGHT / 2;

    protected void initUI() throws MalformedURLException {
        final JFrame frame = new JFrame(TestAnimationFlyAndFrog.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(null);
        final JLabel frog = new JLabel(new ImageIcon(new URL("http://www.iconshock.com/img_jpg/SUPERVISTA/animals/jpg/128/frog_icon.jpg")));
        frog.setSize(frog.getPreferredSize());
        final JLabel fly = new JLabel(new ImageIcon(new URL("http://www.iconshock.com/img_jpg/SUPERVISTA/animals/jpg/128/fly_icon.jpg")));
        fly.setSize(fly.getPreferredSize());
        frame.setMinimumSize(new Rectangle(frog.getPreferredSize()).union(new Rectangle(fly.getPreferredSize())).getSize());
        frame.add(frog);
        frame.add(fly);
        frame.setSize(WIDTH, HEIGHT);
        dxFrog = getNextSpeed() * (random.nextBoolean() ? 1 : -1);
        dyFrog = getNextSpeed() * (random.nextBoolean() ? 1 : -1);
        dxFly = getNextSpeed() * (random.nextBoolean() ? 1 : -1);
        dyFly = getNextSpeed() * (random.nextBoolean() ? 1 : -1);
        Timer t = new Timer(1000 / NB_OF_IMAGES_PER_SECOND, new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                xFrog += dxFrog;
                yFrog += dyFrog;
                if (xFrog + frog.getWidth() > frame.getContentPane().getWidth()) {
                    xFrog = frame.getContentPane().getWidth() - frog.getWidth();
                    dxFrog = -getNextSpeed();
                } else if (xFrog < 0) {
                    xFrog = 0;
                    dxFrog = getNextSpeed();
                }
                if (yFrog + frog.getHeight() > frame.getContentPane().getHeight()) {
                    yFrog = frame.getContentPane().getHeight() - frog.getHeight();
                    dyFrog = -getNextSpeed();
                } else if (yFrog < 0) {
                    yFrog = 0;
                    dyFrog = getNextSpeed();
                }
                frog.setLocation((int) xFrog, (int) yFrog);
                xFly += dxFly;
                yFly += dyFly;
                if (xFly + fly.getWidth() > frame.getContentPane().getWidth()) {
                    xFly = frame.getContentPane().getWidth() - fly.getWidth();
                    dxFly = -getNextSpeed();
                } else if (xFly < 0) {
                    xFly = 0;
                    dxFly = getNextSpeed();
                }
                if (yFly + fly.getHeight() > frame.getContentPane().getHeight()) {
                    yFly = frame.getContentPane().getHeight() - fly.getHeight();
                    dyFly = -getNextSpeed();
                } else if (yFly < 0) {
                    yFly = 0;
                    dyFly = getNextSpeed();
                }
                fly.setLocation((int) xFly, (int) yFly);

            }
        });
        frame.setVisible(true);
        t.start();
    }

    private double getNextSpeed() {
        return 2 * Math.PI * (0.5 + random.nextDouble());
    }

    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException,
            UnsupportedLookAndFeelException {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                try {
                    new TestAnimationFlyAndFrog().initUI();
                } catch (MalformedURLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });
    }
}