Using J2ME Wireless Toolkit 2.0 with one of the default emulators -
Colliding an animated Sprite object with an animated TiledLayer object is producing an IndexOutOfBoundsException from the source line
if (mySprite.collidesWith(tiledLayer, true))
If there is no collision, the line executes normally. Anybody else come across this in MIDP ?
Geez! You're still using tiles! I have developed a quick, pixel perfect method of collision detection that uses fat ray casting and rectangles. However, currently, it is only implemented in my C++ library, Fcatalog. Right now I'm in the process of porting some of my videogame routines to my Java library, Speedy. When I do I will let you know where you can download it.
Here is some code I pieced together to reproduce the error.
There are 2 classes. CollisionTestMidlet which extends MIDlet and CollisionTestCanvas that
extends GameCanvas.Line 70 of CollisionTestCanvas is where the error occurs.
You can get the images it uses at
http://www.microdevnet.com/articles/images/cowboy.png
and
http://www.microdevnet.com/articles/images/tumbleweed.png
They are from a tutorial that has nothing to do with my game.
I am using MIDP 2.0 and J2ME Wireless Toolkit 2.1
Thanks in advance for any light that can be shed on this issue.
//////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CollisionTestMidlet.java
import java.io.IOException;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;
public class CollisionTestMidlet extends MIDlet implements CommandListener
{
private CollisionTestCanvas collisionTestCanvas;
protected void startApp()
{
if (collisionTestCanvas == null)
{
try
{
collisionTestCanvas = new CollisionTestCanvas();
collisionTestCanvas.start();
Command exitCommand = new Command("Exit", Command.EXIT, 0);
collisionTestCanvas.addCommand(exitCommand);
collisionTestCanvas.setCommandListener(this);
}
catch (IOException ioe)
{
System.out.println(ioe);
}
}
Display.getDisplay(this).setCurrent(collisionTestCanvas);
}
protected void pauseApp()
{
}
protected void destroyApp(boolean arg0)
{
if (collisionTestCanvas != null)
collisionTestCanvas.stop();
}
public void commandAction(Command c, Displayable s)
{
if (c.getCommandType() == Command.EXIT)
{
destroyApp(true);
notifyDestroyed();
}
}
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CollisionTestCanvas.java
import java.io.IOException;
import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;
public class CollisionTestCanvas extends GameCanvas implements Runnable
{
private static final int COWBOY_FRAME_WIDTH = 32;
private static final int COWBOY_FRAME_HEIGHT = 48;
private static final int COWBOY_FRAME_COUNT = 4;
private static final int TUMBLEWEED_FRAME_WIDTH = 16;
private static final int TUMBLEWEED_FRAME_HEIGHT = 16;
private static final int TUMBLEWEED_FRAME_COUNT = 3;
private static final int TUMBLEWEED_COUNT = 3;
private boolean isAlive;
private Sprite cowboySprite;
private TiledLayer tumbleweedLayer;
private int animatedTileIndex;
private LayerManager layerManager;
public CollisionTestCanvas() throws IOException
{
super(true);
layerManager = new LayerManager();
createCowboy();
createTumbleweed();
}
private void createCowboy() throws IOException
{
Image image = Image.createImage("/cowboy.png");
cowboySprite = new Sprite(image, COWBOY_FRAME_WIDTH, COWBOY_FRAME_HEIGHT);
cowboySprite.setPosition(0, getHeight() - COWBOY_FRAME_HEIGHT);
layerManager.append(cowboySprite);
}
private void createTumbleweed() throws IOException
{
Image image = Image.createImage("/tumbleweed.png");
tumbleweedLayer = new TiledLayer(TUMBLEWEED_COUNT, 1, image, TUMBLEWEED_FRAME_WIDTH, TUMBLEWEED_FRAME_HEIGHT);
animatedTileIndex = tumbleweedLayer.createAnimatedTile(1);
for (int i = 0; i < TUMBLEWEED_COUNT; i++)
{
tumbleweedLayer.setCell(i, 0, animatedTileIndex);
}
tumbleweedLayer.setAnimatedTile(animatedTileIndex, 1);
tumbleweedLayer.setPosition(getWidth() - (TUMBLEWEED_FRAME_WIDTH*TUMBLEWEED_COUNT), getHeight() - TUMBLEWEED_FRAME_HEIGHT);
layerManager.append(tumbleweedLayer);
}
private void input()
{
int keyStates = getKeyStates();
if ((keyStates & RIGHT_PRESSED) != 0)
{
cowboySprite.move(3, 0);
cowboySprite.nextFrame();
}
}
private void render(Graphics g)
{
// Rectangle collision has no problem
if (cowboySprite.collidesWith(tumbleweedLayer, false))
{
System.out.println("Cowboy and tumbleweed rectangle collision");
}
// Pixel collison throws an ArrayIndexOutOfBoundsException
if (cowboySprite.collidesWith(tumbleweedLayer, true))
{
System.out.println("Cowboy and tumbleweed pixel collision");
}
g.setColor(0xFFFFFF);
g.fillRect(0, 0, getWidth(), getHeight());
tumbleweedLayer.setAnimatedTile(animatedTileIndex,
((tumbleweedLayer.getAnimatedTile(animatedTileIndex) + 1) % TUMBLEWEED_FRAME_COUNT) + 1);
layerManager.paint(g, 0, 0);
flushGraphics();
}
public void start()
{
Thread t = new Thread(this);
isAlive = true;
t.start();
}
public void run()
{
Graphics g = getGraphics();
int timeStep = 80;
while (isAlive)
{
long start = System.currentTimeMillis();
input();
render(g);
long end = System.currentTimeMillis();
int duration = (int)(end - start);
if (duration < timeStep)
{
try {Thread.sleep(timeStep - duration);}catch (InterruptedException ie){}
}
}
}
public void stop()
{
isAlive = false;
}
}
