First Applet Game

Question

I was trying to write snake. After discovering the Timer class, i was able to get the snake to move properly. However, i cant get it to turn. I think I did something wrong with the key listener.
import javax.swing.Timer;
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class Snake extends Applet implements KeyListener
    private int length,dir; //for dir, 2=down, 4=left, 8=up, 6=right
    private int[] snakeX=new int[99];
    private int[] snakeY=new int[99];
    public void init()
        addKeyListener(this);
        length=5;
        dir=6;
        for (int c=0;c<length;c++)
            snakeX[c]=150-20*c;
            snakeY[c]=150;
     * Called by the browser or applet viewer to inform this Applet that it
     * should start its execution. It is called after the init method and
     * each time the Applet is revisited in a Web page.
    public void start()
        int delay = 1000; //milliseconds
        ActionListener taskPerformer = new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                 move();
         new Timer(delay, taskPerformer).start();
    public void update(Graphics g) {
        // Redefine update so it doesn't erase the applet before calling
        // paint().
      paint(g);
     * This may be the most important method in your applet: Here, the
     * drawing of the applet gets done. "paint" gets called everytime the
     * applet should be drawn on the screen. So put the code here that
     * shows the applet.
     * @param  g   the Graphics object for this applet
    public void paint(Graphics g)
        //field
        g.setColor(Color.white);
        g.fillRect(0, 0, 500, 500);
        //snake
        g.setColor(Color.blue);
        for (int c=0;c<length;c++)
            g.fillRect(snakeX[c] ,snakeY[c], 20, 20);
     public void changeDir(int direction)
         dir=direction;
     public void keyTyped(KeyEvent evt) {
         int key = evt.getKeyCode();  // keyboard code for the key that was pressed
         if (key == KeyEvent.VK_LEFT)
            changeDir(4);
         else if (key == KeyEvent.VK_RIGHT)
            changeDir(6);
         else if (key == KeyEvent.VK_UP)
            changeDir(8);
         else if (key == KeyEvent.VK_DOWN)
            changeDir(2);
     public void keyReleased(KeyEvent e) {
     public void keyPressed(KeyEvent e) {                       
    public void move()
        int x=snakeX[0];
        int y=snakeY[0];
        int xChange=0;
        int yChange=0;
        for (int c=length-1;c>0;c--)
            snakeX[c]=snakeX[c-1];
            snakeY[c]=snakeY[c-1];
        switch (dir)
            case 8: yChange=-20; break;
            case 4: xChange=-20; break;
            case 6: xChange=20; break;
            case 2: yChange=20; break;
        snakeX[0]=x+xChange;
        snakeY[0]=y+yChange;
        repaint();
    public boolean isAlive()
        if (snakeX[0]<0 || snakeX[0]>280 || snakeY[0]<0 || snakeY[0]>280)
            return false;
        for (int c=1;c<length;c++)
            if (snakeX[0]==snakeX[c] && snakeY[0]==snakeY[c])
                return false;
        return true;
     * Called by the browser or applet viewer to inform this Applet that
     * it should stop its execution. It is called when the Web page that
     * contains this Applet has been replaced by another page, and also
     * just before the Applet is to be destroyed. If you do not have any
     * resources that you need to release (such as threads that you may
     * want to stop) you can remove this method.
    public void stop()
        // provide any code that needs to be run when page
        // is replaced by another page or before Applet is destroyed
     * Called by the browser or applet viewer to inform this Applet that it
     * is being reclaimed and that it should destroy any resources that it
     * has allocated. The stop method will always be called before destroy.
     * If you do not have any resources that you need to release you can
     * remove this method.
    public void destroy()
        // provide code to be run when Applet is about to be destroyed.
}The Timer creates new thread. I think i need to get the Key Listener into that thread, but Im not sure how to. Please help me do this. (Btw, i know the delay is too long)

Answer 1

this is the code, same with your code but keyTyped is moved to keyPressed, and it is an applet-application game
if playing as applet, be sure to click in the applet area to have it focus
and one thing, there's nothing wrong with the thread
import javax.swing.Timer;
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class Snake extends Applet implements KeyListener{
     private int length,dir; //for dir, 2=down, 4=left, 8=up, 6=right
     private int[] snakeX=new int[99];
     private int[] snakeY=new int[99];
     public void init() {
          addKeyListener(this);
          length=5;
          dir=6;
          for (int c=0;c<length;c++) {
               snakeX[c]=150-20*c;
               snakeY[c]=150;
     public void start() {
          int delay = 1000; //milliseconds
          ActionListener taskPerformer = new ActionListener() {
               public void actionPerformed(ActionEvent evt) {
                    move();
          new Timer(delay, taskPerformer).start();
     public void update(Graphics g) {
          // Redefine update so it doesn't erase the applet before calling
          // paint().
          paint(g);
     public void paint(Graphics g)    {
          //field
          g.setColor(Color.white);
          g.fillRect(0, 0, 500, 500);
          //snake
          g.setColor(Color.blue);
          for (int c=0;c<length;c++) {
               g.fillRect(snakeX[c] ,snakeY[c], 20, 20);
     public void changeDir(int direction)     {
          dir=direction;
     public void keyTyped(KeyEvent evt) {
          // moved to keyPressed(KeyEvent) method
     public void keyReleased(KeyEvent e) { }
     public void keyPressed(KeyEvent e) {
          int key = e.getKeyCode();   // keyboard code for the key that was pressed
          if (key == KeyEvent.VK_LEFT) {
              changeDir(4);
          } else if (key == KeyEvent.VK_RIGHT) {
               changeDir(6);
          } else if (key == KeyEvent.VK_UP) {
               changeDir(8);
          } else if (key == KeyEvent.VK_DOWN) {
               changeDir(2);
     public void move()    {
          int x=snakeX[0];
          int y=snakeY[0];
          int xChange=0;
          int yChange=0;
          for (int c=length-1;c>0;c--)        {
               snakeX[c]=snakeX[c-1];
               snakeY[c]=snakeY[c-1];
          switch (dir)        {
               case 8: yChange=-20; break;
               case 4: xChange=-20; break;
               case 6: xChange=20; break;
               case 2: yChange=20; break;
          snakeX[0]=x+xChange;
          snakeY[0]=y+yChange;
          repaint();
     public boolean isAlive()    {
          if (snakeX[0]<0 || snakeX[0]>280 || snakeY[0]<0 || snakeY[0]>280) {
                return false;
          for (int c=1;c<length;c++) {
               if (snakeX[0]==snakeX[c] && snakeY[0]==snakeY[c]) {
                    return false;
          return true;
     public static void main(String[] args) {
          Snake game = new Snake();
          game.init();
          Frame f = new Frame();
          f.setSize(500, 530);
          f.add(game);
          f.setVisible(true);
          game.start();
          game.requestFocus();
}and you might want to see this: http://goldenstudios.uni.cc/contents/products/games/bin/snake.jnlp