Java Game-Problem with KeyListener

I''m not sure if it is the key listener, try getKeyChar() and see if tht works. If it doesn''t, put a System.out.println() in the key listener to see if it is getting there. It might be that playerX is incrementing but the panel isn''t updating it.

I wouldn''t do it the way you are doing it though. If you look at the Java examples they give you sample 2D stuff. Take classes, something like Surface and AnimatingSurface and put them into your app. That''s what I did until I found LWJGL. Why use normal graphics when you can have OpenGL.

You need to do a few things

1. You need to keep track of when the key is pressed, and when it is released. You get 1 message when it''s pressed, and 1 when it''s released. You would probably have better luck with the way you are doing it by using Typed. Be nice if you created a game action class or something.

2. You should consume the event so nothing else tries to handle it

Tip: If you want to make sure the ship stays in bounds, a simple way is using the modulus operator on the playerx+=1 line and the bounds - eg playerx+=1 % WIND_X

3. Use your timer so your game updates per clock cycle rather then per event recieved. Use a float for this - so if a user manages to move a little bit but not a whole pixel, you don''t loose that little bit each time. Your velocity while moving might be something like 1 pixel / sec - so if a user holds the key for half a second, stops for a second, then presses it for another half second it will move the whole pixel.

to Mr_Ridd: What's the KeyChar for the left and right arrows? Once I find out, I'll try getKeyChar() once I can get my application to register keyPresses and keyReleases-currently, it doesn't pay them any attention. And how can you implement OpenGL in Java?

to paulsdsrubbish: 1.I did that and found out that my application didn't register keyPresses or keyReleases.
2.Sorry, I'm not that advanced in java, what's "consume" mean? And I'll make the boundaries later, I need to get the left/right movement working.
3.I don't get how you'd use a float to track timer events- do you mean to store the character's position?

[edited by - Big Cheez on March 2, 2004 6:21:44 AM]

consume is is in the KeyEvent interface - and yes storing a position in a float.

Find out how long it was since the last time the screen was updated, and move it accordingly to your pixels/sec speed.

I don't think your actionlistener is ever going to be fired - you could do well to repaint on a timer in the code you have yourself at the moment.

This is a simple game loop taken from a book (http://www.amazon.co.uk/exec/obidos/ASIN/1592730051/qid%3D1078229077/202-3486186-4223843 I recommended in another thread (this won't compile unless you have more of the source from the book, but you get the idea):

    /**
        Runs through the game loop until stop() is called.
    */
    public void gameLoop() {
        long startTime = System.currentTimeMillis();
        long currTime = startTime;

        while (isRunning) {
            long elapsedTime =
                System.currentTimeMillis() - currTime;
            currTime += elapsedTime;

            // update

            update(elapsedTime);

            // draw the screen

            Graphics2D g = screen.getGraphics();
            draw(g);
            g.dispose();
            screen.update();

            // don't take a nap! run as fast as possible

            /*try {
                Thread.sleep(20);
            }
            catch (InterruptedException ex) { }*/
        }
 

EDIT: embedded source properly

[edited by - paulsdsrubbish on March 2, 2004 7:09:52 AM]

Yes, ActionListener is fired- I tried it. It''s just the KeyListener.

You tried different keys? Like VK_Z and VK_X just in case?

Your tried implementing only KeyListener rather then both?

Neither of them worked.

[edited by - Big Cheez on March 2, 2004 7:52:28 AM]

First use the BufferedImage.
second
volatile boolean left
KeyPressed(...){
...
if key=left (left=true);


You could use OpenGL from Java by LWJGL. So look at sourceforge and try to find it.

BTW set ignoreRepaint(true);


[edited by - raghar on March 2, 2004 6:06:59 PM]

I think the Javadoc comments have to be immediately before the class. Meaning you can''t put import statements in between the comments and the class.

to yaroslavd: It works. I''ve done stuff before like that and it worked.
to Raghar: what''s setIgnoreRepaint(true) do? And Image worked fine... what''s the advantage to using a BufferedImage? And I tried using

boolean left; 

and

boolean right; 

, it didn''t work.

actionPerformed() contains a repaint(), and when you put some code in there to update the model, you saw a change on the screen.

keyPressed() does not contain a repaint(), and when you put in the same code there to update the model, you didn''t see a change on the screen.

HMM...

But wouldn''t the KeyListener update playerX, and then ActionPerformed be called right after the Timer fired and update the actual image?

What about registering your keyListener? mainFrame.getContentPane().add(mainPanel);
mainFrame.addKeyListener(mainPanel);
JFrame seems to be nice target.
If you have own timer you should do drawind independently on JFrame, so you''d rather disable automatic refresh to prevent unnecessary colisions.
BufferedImage is nicer to Graphics2D, and of course it''s more easily loaded by Java.ImageIO.

Thanx everyone, it works now!

Post the working code then!

/**
 * <p>Title: Swarm</p>
 * <p>Description: Shoot any ship that isn''t yours.</p>
 * <p>Copyright: Copyright (c) 2004</p>
 * <p>Company: Hot Metal Software</p>
 * @author Matthew Dyck a.k.a. Big Cheez
 * @version 1.0
 */

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class Swarm extends JPanel implements KeyListener, ActionListener{
  Image player;
  Timer gameTimer;
  int playerX=0;
  final int WIND_X=800;
  final int WIND_Y=600;
  boolean rapidFire=false;
  boolean doubleBlasters=false;
  boolean syncBlasters=false;
  final int SHOT_DELAY=20;
  final int SYNC_SHOT_DELAY=10;
  boolean lastFired=false;
  final int RAPID_SHOT_DELAY=5;
  boolean laser=false;
  short direction;

  public static void main(String args[]){
    JFrame mainFrame=new JFrame();
    Swarm mainPanel=new Swarm();
    mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    mainFrame.getContentPane().add(mainPanel);
    mainFrame.addKeyListener(mainPanel);
    mainFrame.pack();
    mainFrame.show();
  }
  Swarm(){
    initGraphics();
    initKey();
    iniTimer();
    gameTimer.start();
  }
  void initGraphics(){
    player=getToolkit().getImage("img/player.gif");
  }
  void initKey(){
    addKeyListener(this);
  }
  void iniTimer(){
    gameTimer=new Timer(1,this);
    gameTimer.setInitialDelay(1);
    gameTimer.setCoalesce(true);
  }
  public void keyTyped(KeyEvent k){
  }
  public void keyPressed(KeyEvent k){
    if (k.getKeyCode() == k.VK_RIGHT) {
      direction=1;
      System.out.println("Right");
    }
    if (k.getKeyCode() == k.VK_LEFT) {
      direction=-1;
      System.out.println("Left");
    }
  }
  public void keyReleased(KeyEvent k){
    direction=0;
  }
  public void actionPerformed(ActionEvent a){
    if(direction==1){
      playerX+=2;
    }
    if(direction==-1){
      playerX-=2;
    }
    repaint();
  }
  public void paintComponent(Graphics gOrig){
    Graphics2D g=(Graphics2D)gOrig;
    g.drawImage(player,playerX,WIND_Y-32,this);
  }
}