Moving an Image Across the Screen: Example7Applet

The code below shows the important methods that we had to update the images. The code for the entire applet can be found in Example7Applet.java.

    Image world;
    Image car;

    /**
     * Initialize the applet and compute the delay between frames.
     */
    public void init() {
	String str = getParameter("fps");
	int fps = (str != null) ? Integer.parseInt(str) : 10;
	delay = (fps > 0) ? (1000 / fps) : 100;

	world = getImage(getCodeBase(), "world.gif");
	car = getImage(getCodeBase(), "car.gif");
    }

    /**
     * Paint the previous frame (if any).
     */
    public void paint(Graphics g) {
	update(g);
    }

    /**
     * Paint a frame of animation.
     */
    public void paintFrame(Graphics g) {
	Dimension d = size();
	int w = world.getWidth(this);
	int h = world.getHeight(this);
	
	if ((w > 0) && (h > 0)) {
	    //If we've loaded the world image, draw it.
	    g.drawImage(world, (d.width - w)/2, (d.height - h)/2, this);
	}

	w = car.getWidth(this);
	h = car.getHeight(this);

	if ((w > 0) && (h > 0)) {
	    //If we've loaded the car image...
	    w += d.width;
	    //draw car 1
	    g.drawImage(car, d.width - ((frame * 5) % w), (d.height - h)/3, this);
	    //draw car 2
	    g.drawImage(car, d.width - ((frame * 7) % w), (d.height - h)/2, this);
	}
    }