import java.awt.*;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;

/* 
 * Based on Arthur van Hoff's animation examples, this application
 * can serve as a template for all animation applications.
 */
public class MovingImages extends Frame implements Runnable, MouseListener {
    int frameNumber = -1;
    int delay;
    Thread animatorThread;
    boolean frozen = false;

    Dimension offDimension;
    Image offImage;
    Graphics offGraphics;

    Image stars;
    Image rocket;

    MovingImages(int fps,  String windowTitle) {
        super(windowTitle);
        delay = (fps > 0) ? (1000 / fps) : 100;

        stars=Toolkit.getDefaultToolkit().getImage("./images/starfield.gif");
        rocket=Toolkit.getDefaultToolkit().getImage("./images/rocketship.gif");
        addMouseListener(this);
    }

    public void startAnimation() {
        //Create and start the animating thread.
        if (frozen) {
            //Do nothing.  The user has requested that we
            //stop changing the image.
        } else {
            //Start animating!
            if (animatorThread == null) {
                animatorThread = new Thread(this);
            }
            animatorThread.start();
        }
    }

    public void stopAnimation() {
        //Stop the animating thread.
        animatorThread = null;
    }


    public void mouseClicked(MouseEvent e){
    }
  
    public void mouseEntered(MouseEvent e){
    }
  
    public void mouseExited(MouseEvent e){
    }
  
    public void mousePressed(MouseEvent e){
        if (frozen) {
            frozen = false;
            startAnimation();
        } else {
            frozen = true;
            stopAnimation();
        }
    }
  
    public void mouseReleased(MouseEvent e){
    }

    public void run() {
        //Just to be nice, lower this thread's priority
        //so it can't interfere with other processing going on.
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
 
        //Remember the starting time.
        long startTime = System.currentTimeMillis();

        //This is the animation loop.
        while (Thread.currentThread() == animatorThread) {
            //Advance the animation frame.
            frameNumber++;

            //Display it.
            repaint();

            //Delay depending on how far we are behind.
            try {
                startTime += delay;
                Thread.sleep(Math.max(0, 
                                      startTime-System.currentTimeMillis()));
            } catch (InterruptedException e) {
                break;
            }
        }
    }

    public void update(Graphics g){ 

        paint(g);
    }

    public void paint(Graphics g) {
        Dimension d = getSize();
        //Create the offscreen graphics context, if no good one exists.
        if ( (offGraphics == null)
          || (d.width != offDimension.width)
          || (d.height != offDimension.height) ) {
            offDimension = d;
            offImage = createImage(d.width, d.height);
            offGraphics = offImage.getGraphics();
        }
        paintFrame(offGraphics);
        //Paint the image onto the screen.
        g.drawImage(offImage, 0, 0, this);
    }

void paintFrame(Graphics g) {
    Dimension d = getSize();
    int w;
    int h;

    //If we have a valid width and height for the background image,
    //draw it.
    w = stars.getWidth(this);
    h = stars.getHeight(this);
    if ((w > 0) && (h > 0)) {
        g.drawImage(stars, (d.width - w)/2,
                    (d.height - h)/2, this);
    }

    //If we have a valid width and height for the background image,
    //draw it.
    w = rocket.getWidth(this);
    h = rocket.getHeight(this);
    if ((w > 0) && (h > 0)) {
        g.drawImage(rocket, ((frameNumber*5) % (w + d.width)) - w,
                    (d.height - h)/2, this);
    }
}



    public static void main(String args[]) {
        MovingImages animator = null;
        int fps = 10;

        // Get frames per second from the command line argument
        if (args.length > 0) {
            try {
                fps = Integer.parseInt(args[0]);
            } catch (Exception e) {}
            
        }
        animator = new MovingImages(fps,"Animator");
        animator.setSize(200, 60);
        animator.show();
        animator.startAnimation();
    }

}