Thread: Breakout Game Error

Hi All,

I'm having an issue with the following error, I think its due to the placement of my images? Can someone confirm that:

Exception in thread "main" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(Unknown Source)
at brick.Ball.<init>(Ball.java:18)
at brick.Board.gameInit(Board.java:50)
at brick.Board.addNotify(Board.java:45)
at java.awt.Container.addNotify(Unknown Source)
at javax.swing.JComponent.addNotify(Unknown Source)
at java.awt.Container.addNotify(Unknown Source)
at javax.swing.JComponent.addNotify(Unknown Source)
at java.awt.Container.addNotify(Unknown Source)
at javax.swing.JComponent.addNotify(Unknown Source)
at javax.swing.JRootPane.addNotify(Unknown Source)
at java.awt.Container.addNotify(Unknown Source)
at java.awt.Window.addNotify(Unknown Source)
at java.awt.Frame.addNotify(Unknown Source)
at java.awt.Window.show(Unknown Source)
at java.awt.Component.show(Unknown Source)
at java.awt.Component.setVisible(Unknown Source)
at java.awt.Window.setVisible(Unknown Source)
at brick.BrickGame.<init>(BrickGame.java:16)
at brick.BrickGame.main(BrickGame.java:20)
Exception in thread "Timer-0" java.lang.NullPointerException
at brick.Board$ScheduleTask.run(Board.java:112)
at java.util.TimerThread.mainLoop(Unknown Source)
at java.util.TimerThread.run(Unknown Source)

Heres the code:

Board.java


package brick;

import java.awt.Color;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Point;
import java.awt.Toolkit;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import java.util.Timer;
import java.util.TimerTask;

import javax.swing.JPanel;


public class Board extends JPanel implements Commons {

Image ii;
Timer timer;
String message = "Game Over";
Ball ball;
Paddle paddle;
Brick bricks[];

boolean ingame = true;
int timerId;


public Board() {

addKeyListener(new TAdapter());
setFocusable(true);

bricks = new Brick[30];
setDoubleBuffered(true);
timer = new Timer();
timer.scheduleAtFixedRate(new ScheduleTask(), 1000, 10);
}

public void addNotify() {
super.addNotify();
gameInit();
}

public void gameInit() {

ball = new Ball();
paddle = new Paddle();


int k = 0;
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 6; j++) {
bricks[k] = new Brick(j * 40 + 30, i * 10 + 50);
k++;
}
}
}


public void paint(Graphics g) {
super.paint(g);

if (ingame) {
g.drawImage(ball.getImage(), ball.getX(), ball.getY(),
ball.getWidth(), ball.getHeight(), this);
g.drawImage(paddle.getImage(), paddle.getX(), paddle.getY(),
paddle.getWidth(), paddle.getHeight(), this);

for (int i = 0; i < 30; i++) {
if (!bricks[i].isDestroyed())
g.drawImage(bricks[i].getImage(), bricks[i].getX(),
bricks[i].getY(), bricks[i].getWidth(),
bricks[i].getHeight(), this);
}
} else {

Font font = new Font("Verdana", Font.BOLD, 18);
FontMetrics metr = this.getFontMetrics(font);

g.setColor(Color.BLACK);
g.setFont(font);
g.drawString(message,
(Commons.WIDTH - metr.stringWidth(message)) / 2,
Commons.WIDTH / 2);
}


Toolkit.getDefaultToolkit().sync();
g.dispose();
}

private class TAdapter extends KeyAdapter {

public void keyReleased(KeyEvent e) {
paddle.keyReleased(e);
}

public void keyPressed(KeyEvent e) {
paddle.keyPressed(e);
}
}


class ScheduleTask extends TimerTask {

public void run() {

ball.move();
paddle.move();
checkCollision();
repaint();

}
}

public void stopGame() {
ingame = false;
timer.cancel();
}


public void checkCollision() {

if (ball.getRect().getMaxY() > Commons.BOTTOM) {
stopGame();
}

for (int i = 0, j = 0; i < 30; i++) {
if (bricks[i].isDestroyed()) {
j++;
}
if (j == 30) {
message = "Victory";
stopGame();
}
}

if ((ball.getRect()).intersects(paddle.getRect())) {

int paddleLPos = (int)paddle.getRect().getMinX();
int ballLPos = (int)ball.getRect().getMinX();

int first = paddleLPos + 8;
int second = paddleLPos + 16;
int third = paddleLPos + 24;
int fourth = paddleLPos + 32;

if (ballLPos < first) {
ball.setXDir(-1);
ball.setYDir(-1);
}

if (ballLPos >= first && ballLPos < second) {
ball.setXDir(-1);
ball.setYDir(-1 * ball.getYDir());
}

if (ballLPos >= second && ballLPos < third) {
ball.setXDir(0);
ball.setYDir(-1);
}

if (ballLPos >= third && ballLPos < fourth) {
ball.setXDir(1);
ball.setYDir(-1 * ball.getYDir());
}

if (ballLPos > fourth) {
ball.setXDir(1);
ball.setYDir(-1);
}


}


for (int i = 0; i < 30; i++) {
if ((ball.getRect()).intersects(bricks[i].getRect())) {

int ballLeft = (int)ball.getRect().getMinX();
int ballHeight = (int)ball.getRect().getHeight();
int ballWidth = (int)ball.getRect().getWidth();
int ballTop = (int)ball.getRect().getMinY();

Point pointRight =
new Point(ballLeft + ballWidth + 1, ballTop);
Point pointLeft = new Point(ballLeft - 1, ballTop);
Point pointTop = new Point(ballLeft, ballTop - 1);
Point pointBottom =
new Point(ballLeft, ballTop + ballHeight + 1);

if (!bricks[i].isDestroyed()) {
if (bricks[i].getRect().contains(pointRight)) {
ball.setXDir(-1);
}

else if (bricks[i].getRect().contains(pointLeft)) {
ball.setXDir(1);
}

if (bricks[i].getRect().contains(pointTop)) {
ball.setYDir(1);
}

else if (bricks[i].getRect().contains(pointBottom)) {
ball.setYDir(-1);
}

bricks[i].setDestroyed(true);
}
}
}
}
}



Paddle.java



package brick;

import java.awt.event.KeyEvent;

import javax.swing.ImageIcon;


public class Paddle extends Sprite implements Commons {

String paddle = "../images/paddle.png";

int dx;

public Paddle() {

ImageIcon ii = new ImageIcon(this.getClass().getResource(paddle));
image = ii.getImage();

width = image.getWidth(null);
heigth = image.getHeight(null);

resetState();

}

public void move() {
x += dx;
if (x <= 2)
x = 2;
if (x >= Commons.PADDLE_RIGHT)
x = Commons.PADDLE_RIGHT;
}

public void keyPressed(KeyEvent e) {

int key = e.getKeyCode();

if (key == KeyEvent.VK_LEFT) {
dx = -2;

}

if (key == KeyEvent.VK_RIGHT) {
dx = 2;
}
}

public void keyReleased(KeyEvent e) {
int key = e.getKeyCode();

if (key == KeyEvent.VK_LEFT) {
dx = 0;
}

if (key == KeyEvent.VK_RIGHT) {
dx = 0;
}
}

public void resetState() {
x = 200;
y = 360;
}
}



Ball.java



package brick;

import javax.swing.ImageIcon;


public class Ball extends Sprite implements Commons {

private int xdir;
private int ydir;

protected String ball = "../images/ball.png";

public Ball() {

xdir = 1;
ydir = -1;

ImageIcon ii = new ImageIcon(this.getClass().getResource(ball));
image = ii.getImage();

width = image.getWidth(null);
heigth = image.getHeight(null);

resetState();
}


public void move()
{
x += xdir;
y += ydir;

if (x == 0) {
setXDir(1);
}

if (x == BALL_RIGHT) {
setXDir(-1);
}

if (y == 0) {
setYDir(1);
}
}

public void resetState()
{
x = 230;
y = 355;
}

public void setXDir(int x)
{
xdir = x;
}

public void setYDir(int y)
{
ydir = y;
}

public int getYDir()
{
return ydir;
}
}



BrickGame.java



package brick;

import javax.swing.JFrame;

public class BrickGame extends JFrame {

public BrickGame()
{
add(new Board());
setTitle("Breakout");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(Commons.WIDTH, Commons.HEIGTH);
setLocationRelativeTo(null);
setIgnoreRepaint(true);
setResizable(false);
setVisible(true);
}

public static void main(String[] args) {
new BrickGame();
}
}


Sprite.java

package brick;

import java.awt.Image;
import java.awt.Rectangle;

public class Sprite {

protected int x;
protected int y;
protected int width;
protected int heigth;
protected Image image;


public void setX(int x) {
this.x = x;
}

public int getX() {
return x;
}

public void setY(int y) {
this.y = y;
}

public int getY() {
return y;
}

public int getWidth() {
return width;
}

public int getHeight() {
return heigth;
}

Image getImage()
{
return image;
}

Rectangle getRect()
{
return new Rectangle(x, y,
image.getWidth(null), image.getHeight(null));
}
}

Commons.java


package brick;

public interface Commons {
public static final int WIDTH = 300;
public static final int HEIGTH = 400;
public static final int BOTTOM = 390;
public static final int PADDLE_RIGHT = 250;
public static final int BALL_RIGHT = 280;
}

[B]Brick.java[B]

package brick;

import javax.swing.ImageIcon;


public class Brick extends Sprite {

String brickie = "../images/brickie.png";

boolean destroyed;


public Brick(int x, int y) {
this.x = x;
this.y = y;

ImageIcon ii = new ImageIcon(this.getClass().getResource(brickie));
image = ii.getImage();

width = image.getWidth(null);
heigth = image.getHeight(null);

destroyed = false;
}

public boolean isDestroyed()
{
return destroyed;
}

public void setDestroyed(boolean destroyed)
{
this.destroyed = destroyed;
}

}

The lines in bold have been highlighted by the compiler:

public Ball() {

xdir = 1;
ydir = -1;

ImageIcon ii = new ImageIcon(this.getClass().getResource(ball));
image = ii.getImage();

width = image.getWidth(null);
heigth = image.getHeight(null);

resetState();
}


public void gameInit() {

ball = new Ball();
paddle = new Paddle();

public void addNotify() {
super.addNotify();
gameInit();
}

class ScheduleTask extends TimerTask {

public void run() {

ball.move();
paddle.move();
checkCollision();
repaint();

}