Runtime error accessing ArrayList

Question

These 2 classes are basically the classes from the book developing games in java, without the fullscreen stuff. They are supposed to create an animation. They both compile fine but when I run I get an error message, an no animation, paint() is only called once. Here's the error message:
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 4, Size: 4
at java.util.ArrayList.RangeCheck(ArrayList.java:546)
at java.util.ArrayList.get(ArrayList.java:321)
at Animation.getFrame(Animation.java:60)
at Animation.update(Animation.java:43)
at AnimationTest1.animationLoop(AnimationTest1.java:58)
at AnimationTest1.run(AnimationTest1.java:44)
at AnimationTest1.main(AnimationTest1.java:10)
I think this means the program is trying to access frame 4 when there is none. Right? I just can't get my brain around this. Any help would be great!
import java.awt.Image;
import java.util.ArrayList;
/*     this class manages a serie of images (frames) and the amount of time to
     display each frame */
public class Animation {
     private ArrayList frames;
     private int currFrameIndex;
     private long animTime;
     private long totalDuration;
     //creates a new, empty animation, calls start().
     public Animation() {
          frames = new ArrayList();
          totalDuration = 0;
          start();
     //adds an image to the animation, + how long to display the image.
     public synchronized void addFrame(Image image, long duration) {
          totalDuration += duration;
          frames.add(new AnimFrame(image, totalDuration));
     //starts this animation over from the beginning .
     public synchronized void start() {
          animTime = 0;
          currFrameIndex = 0;
     //updates this animations current frame if necessary
     public synchronized void update(long elapsedTime) {
          if (frames.size() >1) {
               animTime += elapsedTime;
               if (animTime >= totalDuration) {
                    animTime = animTime % totalDuration;
                    currFrameIndex = 0;
               while (animTime > getFrame(currFrameIndex).endTime) {
                    currFrameIndex ++;
     //gets the animations current frame. null if none availible.
     public synchronized Image getImage() {
          if (frames.size() == 0) {
               return null;
          else {
               return getFrame(currFrameIndex).image;
     private AnimFrame getFrame(int i) {
          return (AnimFrame)frames.get(i);
     private class AnimFrame {
          Image image;
          long endTime;
          public AnimFrame(Image image, long endtime) {
               this.image = image;
               this.endTime = endTime;
import java.awt.*;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
public class AnimationTest1 {
     public static void main (String args[]) {          
          AnimationTest1 test = new AnimationTest1();
          test.run();
     private static final long DEMO_TIME = 5000;
     private JFrame frame;
     private Animation anim;
     public void loadImages() {
          //load images
          Image player1 = loadImage("gif1.png");
          Image player2 = loadImage("gif2.png");
          Image player3 = loadImage("gif3.png");
          //create animation
          anim = new Animation();
          anim.addFrame(player1, 200);
          anim.addFrame(player2, 200);
          anim.addFrame(player3, 200);
          anim.addFrame(player2, 200);
     //loads image with ImageIcon
     private Image loadImage(String filename) {
          return new ImageIcon(filename).getImage();
     public void run() {
          try {
               frame = new JFrame();
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
               frame.setSize(300, 300);
               frame.setVisible(true);
               loadImages();
               animationLoop();
          finally {
     public void animationLoop() {
          long startTime = System.currentTimeMillis();
          long currTime = startTime;
          while (currTime - startTime < DEMO_TIME) {
               long elapsedTime = System.currentTimeMillis() - currTime;
               currTime += elapsedTime;
               anim.update(elapsedTime);
               //getContentpane.getgraphics??!!
               Graphics g = frame.getGraphics();
               draw(g);
               g.dispose();
               try {
                    Thread.sleep(20);
               catch (InterruptedException ex) {}
     //draw the animation
     public void draw(Graphics g) {
          g.setColor(Color.white);
          g.fillRect(0, 0, 300, 300);          
          g.drawImage(anim.getImage(), 0, 0, null);
}

Answer 1

106498II wrote:
i changed it to read:
while (animTime > getFrame(currFrameIndex).endTime) {
                    currFrameIndex ++;
                    if (currFrameIndex >3) {
                         currFrameIndex = 0;
                    }this gets rid of the error but still no animation. Perhaps its something to do with that I draw directly on the JFrame?On the JFrame? Better to draw in a JPanel or JComponent. Also, perhaps you're trying to animate on the EDT in which case you get the beginning picture, and the end picture but usually you get nothing in between. Are you using a non-EDT thread or a Swing Timer?
Addendum: yeah it looks like you're trying to put the EDT (event dispatch thread -- the main thread that runs Swing) to sleep here. Please don't do this. Also you're trying to draw outside of a paint or paintComponent method.
Solution: Run don't walk to the Sun java2D and Swing graphics tutorials and read and study them.
Edited by: petes1234 on Dec 11, 2007 7:21 PM