Develop Reference

How to set speed of playermovement in Java 2D platform game

I am following this tutorial on how to create a Java2D platform game. I followed the code precisely, but when I tried to run it, the player moves way too fast when moving left and when jumping and falling compared to when it's moving right.
My player class looks like this:
package Entity;
import TileMap.*;
import java.awt.*;
import java.util.ArrayList;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
public class Player extends MapObject {
// Player stats
private int health, maxHealth, fire, maxFire, fireCost, fireBallDamage, scratchDamage, scratchRange;
private boolean dead, flinching, firing, scratching, gliding;
private long flinchTimer;
// private ArrayList<FireBall> fireballs;
private ArrayList<BufferedImage[]> sprites;
private final int[] numFrames = { 2, 8, 1, 2, 4, 2, 5 };
// Animation actions
private static final int IDLE = 0;
private static final int WALKING = 1;
private static final int JUMPING = 2;
private static final int FALLING = 3;
private static final int GLIDING = 4;
private static final int FIREBALL = 5;
private static final int SCRATCHING = 6;
private int currentAction;
// Constructor
public Player(TileMap tm) {
super(tm);
width = height = 30;
cWidth = cHeight = 20;
moveSpeed = 0.3;
maxSpeed = 1.6;
stopSpeed = 0.4;
fallSpeed = 0.15;
maxFallSpeed = 4.0;
jumpStart = -4.8;
stopJumpSpeed = 0.3;
facingRight = true;
health = maxHealth = 5;
fire = maxFire = 2500;
fireCost = 200;
fireBallDamage = 5;
//fireBalls = new ArrayList<FireBall>();
scratchDamage = 8;
scratchRange = 40;
// Load sprites
try {
BufferedImage spritesheet =
ImageIO.read( getClass().getResourceAsStream("/Sprites/Player/playersprites.gif"));
sprites = new ArrayList<BufferedImage[]>();
// Loop through animation actions
for (int i = 0; i < 7; i++){
BufferedImage[] bi = new BufferedImage[numFrames[i]];
for (int j = 0; j < numFrames[i]; j++) {
// numFrames[6] = SCRATCH has width = 60
if (i != 6) {
bi[j] = spritesheet.getSubimage(j * width, i * height, width, height);
} else {
bi[j] = spritesheet.getSubimage(j * width * 2, i * height, width, height);
}
}
sprites.add(bi); // Add BufferedImageArray to animations list
}
} catch (Exception e) { e.printStackTrace(); }
animation = new Animation();
currentAction = IDLE;
animation.setFrames(sprites.get(IDLE));
animation.setDelay(400);
}
// Getters
public int getHealth() { return health; }
public int getMaxHealth() { return maxHealth; }
public int getFire() { return fire; }
public int getMaxFire() { return maxFire; }
// Setters
public void setFiring() { firing = true; }
public void setScratching() { scratching = true; }
public void setGliding(boolean b) { gliding = b; }
private void getNextPosition() {
// Movement
if (left) {
dx -= moveSpeed;
if ( dx < -maxSpeed) { dx = 0; }
} else if (right) {
dx += moveSpeed;
if (dx > maxSpeed) { dx = maxSpeed; }
} else {
if (dx > 0) {
dx -= stopSpeed;
if ( dx < 0 ) { dx = 0; }
} else if (dx < 0) {
dx += stopSpeed;
if (dx > 0) { dx = 0; }
}
}
// Cannot attack while moving, unless in the air
if ( currentAction == SCRATCHING || currentAction == FIREBALL && !( jumping || falling)) { dx = 0; }
// Jumping
if (jumping && !falling) {
dy += jumpStart;
falling = true;
}
if (falling) {
if ( dy > 0 && gliding) { dy += fallSpeed * 0.1; }
else { dy += fallSpeed; }
if ( dy > 0 ) { jumping = false; }
if ( dy < 0 && !jumping ) { dy += maxFallSpeed; }
if ( dy > maxFallSpeed ) { dy = maxFallSpeed; }
}
}
public void update() {
// Update position
getNextPosition();
checkTileMapCollision();
setPosition(xtemp, ytemp);
// Set animations
if (scratching) {
if (currentAction != SCRATCHING) {
currentAction = SCRATCHING;
animation.setFrames(sprites.get(SCRATCHING));
animation.setDelay(50);
width = 60;
}
} else if (firing) {
if (currentAction != FIREBALL) {
currentAction = FIREBALL;
animation.setFrames(sprites.get(FIREBALL));
animation.setDelay(100);
width = 30;
}
} else if (dy > 0) {
if (gliding) {
if (currentAction != GLIDING) {
currentAction = GLIDING;
animation.setFrames(sprites.get(GLIDING));
animation.setDelay(100);
width = 30;
}
} else if (currentAction != FALLING) {
currentAction = FALLING;
animation.setFrames(sprites.get(FALLING));
animation.setDelay(100);
width = 30;
}
} else if (dy < 0) {
if ( currentAction != JUMPING) {
currentAction = JUMPING;
animation.setFrames(sprites.get(JUMPING));
animation.setDelay(-1);
width = 30;
}
} else if ( left || right ) {
if ( currentAction != WALKING) {
currentAction = WALKING;
animation.setFrames(sprites.get(WALKING));
animation.setDelay(40);
width = 30;
}
} else {
if ( currentAction != IDLE) {
currentAction = IDLE;
animation.setFrames(sprites.get(IDLE));
animation.setDelay(400);
width = 30;
}
}
animation.update();
// Set direction
if ( currentAction != SCRATCHING && currentAction != FIREBALL) {
if ( right) { facingRight = true; }
if ( left ) { facingRight = false; }
}
}
public void draw(Graphics2D g) {
setMapPosition();
// Draw player
if (flinching) {
long elapsed = (System.nanoTime() - flinchTimer) / 1000000;
if (elapsed / 100 % 2 == 0) { return; } // Gives the appearance of blinking
}
if (facingRight) {
g.drawImage(animation.getImage(), (int) (x + xmap - width/2), (int) (y + ymap - height/2), null);
} else {
g.drawImage(animation.getImage(), (int) (x + xmap - width/2 + width), (int) (y + ymap - height/2),
-width, height, null);
}
}
}
I tried changing
private void getNextPosition() {
// Movement
if (left) {
dx -= moveSpeed;
if ( dx < -maxSpeed) { dx = -maxSpeed; }
to
private void getNextPosition() {
// Movement
if (left) {
dx -= moveSpeed;
if ( dx < -maxSpeed) { dx = 0; }
Which helped for the left-movement, but it created a lag in the graphics, so I tried changing theAnimation-class which looks like this:
package Entity;
import java.awt.image.BufferedImage;
public class Animation {
private BufferedImage[] frames;
private int currentFrame;
private long startTime, delay;
private boolean playedOnce;
public void Animation() {
playedOnce = false;
}
public void setFrames(BufferedImage[] frames) {
this.frames = frames;
currentFrame = 0;
startTime = System.nanoTime();
playedOnce = false;
}
public void setDelay(long d) { delay = d; }
public void setFrame(int i) { currentFrame = i; }
public void update() {
if (delay == -1) { return; }
long elapsed = (System.nanoTime() - startTime) / 1000000;
if (elapsed > delay) {
currentFrame++;
startTime = System.nanoTime();
}
if (currentFrame == frames.length) {
currentFrame = 0;
playedOnce = true;
}
}
public int getFrame() { return currentFrame; }
public BufferedImage getImage() { return frames[currentFrame]; }
public boolean hasPlayedOnce() { return playedOnce; }
}
Which I thought was where I could fix the problem, but I am uncertain as I am new to gamelogic. Is there any way I can slow down the movement of the player? All help is appreciated!

Can't seem to access the image file in my PlayerClass even though it is properly loaded

I'm creating a 2D java game and ran into a nullpointer exception. Whenever I call my render in the playstate class, it throws the exception. I had previously rendered the Font file and got it to work when commenting out the player object references. The player "linkformatted.png" file is able to load after trying and catching, but the nullpointer exception stays. Changing the values didn't work.
public class PlayState extends GameState {
private Font font;
private Player player;
public PlayState(GameStateManager gsm) {
super(gsm);
font = new Font("font/ZeldaFont.png", 16, 16);
player = new Player(new Sprite("entity/linkformatted.png"), new Vector2f(100, 100), 32);
}
public void update() {
player.update();
}
public void input(MouseHandler mouse, KeyHandler key) {
player.input(mouse, key);
}
public void render(Graphics2D g) {
Sprite.drawArray(g, font, "YOU", new Vector2f(100, 100), 32, 32, 16, 0);
player.render(g);
}
}
public class Sprite {
private BufferedImage SPRITESHEET = null;
private BufferedImage[][] spriteArray;
private final int TILE_SIZE = 32;
public int w;
public int h;
private int wSprite;
private int hSprite;
public Sprite(String file) {
w = TILE_SIZE;
h = TILE_SIZE;
System.out.println("Loading: " + file + "...");
SPRITESHEET = loadSprite(file);
wSprite = SPRITESHEET.getWidth() / w;
hSprite = SPRITESHEET.getHeight() / h;
loadSpriteArray();
}
public Sprite(String file, int w, int h) {
this.w = w;
this.h = h;
System.out.println("Loading: " + file + "...");
SPRITESHEET = loadSprite(file);
wSprite = SPRITESHEET.getWidth() / w;
hSprite = SPRITESHEET.getHeight() / h;
loadSpriteArray();
}
public void setSize(int width, int height) {
setWidth(width);
setHeight(height);
}
public void setWidth(int i) {
w = i;
wSprite = SPRITESHEET.getWidth() / w;
}
public void setHeight(int i) {
h = i;
hSprite = SPRITESHEET.getHeight() / h;
}
public int getWidth() {
return w;
}
public int getHeight() {
return h;
}
private BufferedImage loadSprite(String file) {
BufferedImage sprite = null;
try {
sprite = ImageIO.read(getClass().getClassLoader().getResourceAsStream(file));
} catch(Exception e) {
System.out.println("Error: could not load file: " + file);
}
return sprite;
}
public void loadSpriteArray() {
spriteArray = new BufferedImage[wSprite][hSprite];
for(int x = 0; x < wSprite; x++) {
for(int y = 0; y < hSprite; y++) {
spriteArray[x][y] = getSprite(x, y);
}
}
}
public BufferedImage getSpriteSheet() {
return SPRITESHEET;
}
public BufferedImage getSprite(int x, int y) {
return SPRITESHEET.getSubimage(x * w, y * h, w, h);
}
public BufferedImage[] getSpriteArray(int i) {
return spriteArray[i];
}
public BufferedImage[][] getSpriteArray2(int i) {
return spriteArray;
}
public static void drawArray(Graphics2D g, ArrayList<BufferedImage> img, Vector2f pos, int width, int height, int xOffset, int yOffset) {
float x = pos.x;
float y = pos.y;
for(int i = 0; i < img.size(); i++) {
if(img.get(i) != null) {
g.drawImage(img.get(i), (int) x, (int) y, width, height, null);
}
x += xOffset;
y += yOffset;
}
}
public static void drawArray(Graphics2D g, Font f, String word, Vector2f pos, int width, int height, int xOffset, int yOffset) {
float x = pos.x;
float y = pos.y;
for(int i = 0; i < word.length(); i++ ) {
if(word.charAt(i) != 32); // the space
g.drawImage(f.getFont(word.charAt(i)), (int) x, (int) y, width, height, null);
x += xOffset;
y += yOffset;
}
}
}
public class Animation {
private BufferedImage[] frames;
private int currentFrame;
private int numFrames;
private int count;
private int delay;
private int timesPlayed;
public Animation(BufferedImage[] frames) {
timesPlayed = 0;
setFrames(frames);
}
public Animation() {
timesPlayed = 0;
}
public void setFrames(BufferedImage[] frames) {
frames = frames;
currentFrame = 0;
timesPlayed = 0;
delay = 2;
numFrames = frames.length;
}
public void setDelay(int i) { delay = i;}
public void setFrame(int i) { currentFrame = i;}
public void setNumFrames(int i) { numFrames = i;}
public void update() {
if(delay == -1) return;
count++;
if(count == delay) {
currentFrame++;
count = 0;
}
if(currentFrame == numFrames) {
currentFrame = 0;
timesPlayed++;
}
}
public int getDelay() {
return delay;
}
public int getFrame() {
return currentFrame;
}
public int getCount() {
return count;
}
public BufferedImage getImage() {
return frames[currentFrame];
}
public boolean hasPlayedOnce() {
return timesPlayed > 0;
}
public boolean hasPlayed(int i) {
return timesPlayed == i;
}
}
public class Player extends Entity {
public Player(Sprite sprite, Vector2f origin, int size) {
super(sprite, origin, size);
}
public void move() {
if(up) {
dy -= acc;
if(dy < -maxSpeed) {
dy = -maxSpeed;
}
} else {
if(dy < 0) {
dy += deacc;
if(dy > 0) {
dy = 0;
}
}
}
if(down) {
dy += acc;
if(dy < maxSpeed) {
dy = maxSpeed;
}
} else {
if(dy > 0) {
dy -= deacc;
if(dy < 0) {
dy = 0;
}
}
}
if(left) {
dx -= acc;
if(dx < -maxSpeed) {
dy = -maxSpeed;
}
} else {
if(dx < 0) {
dx += deacc;
if(dx > 0) {
dx = 0;
}
}
}
if(right) {
dx += acc;
if(dx > maxSpeed) {
dy = maxSpeed;
}
} else {
if(dx > 0) {
dx -= deacc;
if(dx < 0) {
dx = 0;
}
}
}
}
public void update() {
super.update();
move();
pos.x = dx;
pos.y = dy;
}
#Override
public void render(Graphics2D g) {
g.drawImage(ani.getImage(), (int) (pos.x), (int) (pos.y), size, size, null);
}
public void input(MouseHandler mouse, KeyHandler key) {
if(key.up.down) {
up = true;
} else {
up = false;
}
if(key.down.down) {
down = true;
} else {
down = false;
}
if(key.left.down) {
left = true;
} else {
left = false;
}
if(key.right.down) {
right = true;
} else {
right = false;
}
if(key.attack.down) {
attack = true;
} else {
attack = false;
}
}
}
Here is what is printed:
Loading: entity/linkformatted.png...
Exception in thread "GameThread" java.lang.NullPointerException
at com.zwellis.game.graphics.Animation.getImage(Animation.java:62)
at com.zwellis.game.entity.Player.render(Player.java:82)
at com.zwellis.game.states.PlayState.render(PlayState.java:34)
at com.zwellis.game.states.GameStateManager.render(GameStateManager.java:71)
at com.zwellis.game.GamePanel.render(GamePanel.java:133)
at com.zwellis.game.GamePanel.run(GamePanel.java:90)
at java.base/java.lang.Thread.run(Thread.java:834)
Here is what happens when I made another file to display the image:
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
public class ImageInFrame {
public static void main(String[] args) throws IOException {
String path = "entity/linkformatted.png";
File file = new File(path);
BufferedImage image = ImageIO.read(file);
JLabel label = new JLabel(new ImageIcon(image));
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().add(label);
f.pack();
f.setLocation(200,200);
f.setVisible(true);
}
}
Here is what happens:
Exception in thread "main" javax.imageio.IIOException: Can't read input file!
at java.desktop/javax.imageio.ImageIO.read(ImageIO.java:1308)
at ImageInFrame.main(ImageInFrame.java:11)
Here is also the github link
https://github.com/xfyktcl/ZwellisKnight.git

JFrame sprite sheet black screen

So I have been trying to follow a tutorial
But it isn't working. It is a tutorial on making a sprite sheet with JFrame. I could get other things to work, but for some reason this won't. It is supposed to display a tiled image, but instead it displays a black screen.
Game.java
package ca.colescheler.game;
import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import javax.swing.JFrame;
import ca.colescheler.game.gfx.Screen;
import ca.colescheler.game.gfx.SpriteSheet;
#SuppressWarnings("unused")
public class Game extends Canvas implements Runnable {
/**
*
*/
private static final long serialVersionUID = 9086760045199246082L;
private BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
private int[] pixels = ((DataBufferInt) image.getRaster().getDataBuffer()).getData();
public boolean running;
private static final long serialVesionUID = 1;
public static final int WIDTH = 160;
public static final int HEIGHT = WIDTH/12*9;
public static final int SCALE=3;
public static final String NAME="Game";
private JFrame frame;
int tickCount=1;
private SpriteSheet spriteSheet = new SpriteSheet("/sprite_sheet.png");
private Screen screen;
public static long getSerialvesionuid() {
return serialVesionUID;
}
public Game() {
setMinimumSize(new Dimension(WIDTH*SCALE,HEIGHT*SCALE));
setMaximumSize(new Dimension(WIDTH*SCALE,HEIGHT*SCALE));
setPreferredSize(new Dimension(WIDTH*SCALE,HEIGHT*SCALE));
frame = new JFrame(NAME);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(this, BorderLayout.CENTER);
frame.pack();
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public void init() {
screen = new Screen(WIDTH,HEIGHT,new SpriteSheet("/sprite_sheet.png"));
}
public void tick() {
tickCount++;
}
long now = System.nanoTime();
public synchronized void stop() {
// TODO Auto-generated method stub
}
public synchronized void start() {
// TODO Auto-generated method stub
//new Thread(this).start();
running = true;
run();
frames = 1;
ticks = 1;
}
static int frames = 0;
static int ticks = 0;
public void run() {
long lastTime = System.nanoTime();
double nsPerTick = 1000000000d/60d;
long lastTimer = System.currentTimeMillis();
double delta=0;
while (running) {
init();
long now = System.nanoTime();
delta += (now - lastTime) / nsPerTick;
lastTime = now;
boolean shouldRender = false;
while (delta >= 1) {
ticks++;
tick();
delta -= 1;
shouldRender = true;
}
if (shouldRender) {
render();
}
if (System.currentTimeMillis() - lastTimer > 1000) {
lastTimer += 1000;
System.out.println(frames + ", " + ticks);
frames=0;
ticks=0;
}
}
}
public void render() {
BufferStrategy bs = this.getBufferStrategy();
if (bs == null) {
this.createBufferStrategy(3);
return;
}
screen.render(pixels, 0, WIDTH);
Graphics g = bs.getDrawGraphics();
//g.drawRect(0, 0, getWidth(), getHeight());
//g.drawImage(image, 0, 0, getWidth(), getHeight(), null);
g.dispose();
bs.show();
}
public static void main(String args[]) {
new Game().start();
}
}
SpriteSheet.java
package ca.colescheler.game.gfx;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
public class SpriteSheet {
public String path;
public int width;
public int height;
public int[] pixels;
public SpriteSheet(String path) {
BufferedImage image = null;
try {
image = ImageIO.read(SpriteSheet.class.getResourceAsStream(path));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (image == null) {
return;
}
this.path = path;
this.width = image.getWidth();
this.height = image.getHeight();
pixels = image.getRGB(0, 0, width, height, null, 0, width);
//AARRGGBB
for (int i=0; i<pixels.length;i++) {
pixels[i] = (pixels[i] & 0xff)/64;
}
for(int i=0; i<8;i++) {
System.out.println(pixels[i]);
}
//85*0
}
}
Screen.java
package ca.colescheler.game.gfx;
public class Screen {
public static final int MAP_WIDTH = 64;
public static final int MAP_WIDTH_MASK = MAP_WIDTH - 1;
public int[] tiles = new int[MAP_WIDTH * MAP_WIDTH];
public int[] colours = new int[MAP_WIDTH * MAP_WIDTH * 4];
public int xOffset = 0;
public int yOffset = 0;
public int width;
public int height;
public SpriteSheet sheet;
public Screen(int width, int height, SpriteSheet sheet) {
this.width = width;
this.height = height;
this.sheet = sheet;
for (int i=1;i<MAP_WIDTH*MAP_WIDTH;i++) {
colours[i*4+0] = 0xff00ff;
colours[i*4+1] = 0x00ffff;
colours[i*4+2] = 0xffff00;
colours[i*4+3] = 0xffffff;
}
}
public void render(int[] pixels, int offset, int row) {
for (int yTile = yOffset>>3;yTile <-(yOffset + height) >>3; yTile++) {
int yMin = yTile * 8 - yOffset;
int yMax = yMin + 8;
if (yMin < 0) yMin = 0;
if (yMax > height) yMax = height;
for (int xTile = xOffset >>3; xTile <=(xOffset+width) >>3; xTile++) {
int xMin = xTile * 8 - xOffset;
int xMax = xMin + 8;
if (xMin < 0) xMin = 0;
if (xMax > width) xMax = height;
int tileIndex = (xTile &(MAP_WIDTH_MASK)) + (yTile & (MAP_WIDTH_MASK)) * MAP_WIDTH;
for (int y = yMin;y<yMax;y++) {
int sheetPixel = ((y+yOffset) & 7) * sheet.width + ((xMin + xOffset) & 7);
int tilePixel = offset + xMin + y * row;
for (int x=xMin; x<xMax;x++) {
int colour = tileIndex * 4 + sheet.pixels[sheetPixel++];
pixels[tilePixel++]=colours[colour];
}
}
}
}
}}
Link to tutorial

In the file Screen.java, there is a typo. You should change height to width in the following line:
if (xMax > width) xMax = height;

Getting a NullPointerException for some reason

I'm following a tutorial from theChernoProject, however in episode 22 i keep getting a nullPointerException whem trying to render the pixels array from the sprite ?
Error:
Exception in thread "Game" java.lang.ExceptionInInitializerError
at com.santec.game.learning.thecherno.graphics.Screen.render(Screen.java:40)
at com.santec.game.learning.thecherno.Game.render(Game.java:109)
at com.santec.game.learning.thecherno.Game.run(Game.java:78)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at com.santec.game.learning.thecherno.graphics.Sprite.load(Sprite.java:23)
at com.santec.game.learning.thecherno.graphics.Sprite.<init>(Sprite.java:17)
at com.santec.game.learning.thecherno.graphics.Sprite.<clinit>(Sprite.java:10)
... 4 more
Classes:
Game.java :
package com.santec.game.learning.thecherno;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import javax.swing.JFrame;
import com.santec.game.learning.thecherno.graphics.Screen;
import com.santec.game.learning.thecherno.input.Keyboard;
public class Game extends Canvas implements Runnable {
private static final long serialVersionUID = 1L;
public static int width = 300;
public static int height = width / 16 * 9;
public static int scale = 3;
public static String title = "Rain";
private Thread thread;
private JFrame frame;
private boolean running = false;
private Screen screen;
private Keyboard key;
private BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
private int[] pixels = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();
public Game() {
Dimension size = new Dimension(width * scale, height * scale);
setPreferredSize(size);
screen = new Screen(width, height);
frame = new JFrame();
key = new Keyboard();
addKeyListener(key);
}
public synchronized void start() {
running = true;
thread = new Thread(this, "Game");
thread.start();
}
public synchronized void stop() {
running = false;
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public void run() {
long lastTime = System.nanoTime();
long timer = System.currentTimeMillis();
final double ns = 1000000000.0 / 60.0;
double delta = 0;
int frames = 0;
int updates = 0;
while(running) {
long now = System.nanoTime();
delta += (now - lastTime) / ns;
lastTime = now;
while(delta >= 1) {
update();
updates++;
delta--;
}
render();
frames++;
if(System.currentTimeMillis() - timer > 1000) {
timer += 1000;
frame.setTitle(title + ": " + updates + " ups | " + frames + " fps");
updates = 0;
frames = 0;
}
}
stop();
}
int x = 0, y = 0;
public void update() {
key.update();
if(key.up) y--;
if(key.down) y++;
if(key.right) x++;
if(key.left) x--;
}
public void render() {
BufferStrategy bs = getBufferStrategy();
if(bs == null) {
createBufferStrategy(3);
return;
}
screen.clear();
screen.render(x, y);
for(int i = 0; i < pixels.length; i++) {
pixels[i] = screen.pixels[i];
}
Graphics g = bs.getDrawGraphics();
{
g.setColor(Color.cyan);
g.drawImage(image, 0, 0, getWidth(), getHeight(), null);
}
g.dispose();
bs.show();
}
public static void main(String[] args) {
Game game = new Game();
game.frame.setResizable(false);
game.frame.setTitle(game.title);
game.frame.add(game);
game.frame.pack();
game.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
game.frame.setLocationRelativeTo(null);
game.frame.setVisible(true);
game.start();
}
}
graphics/SpriteSheet.java :
package com.santec.game.learning.thecherno.graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
public class SpriteSheet {
private String path;
public final int SIZE;
public int[] pixels;
// Spritesheets
public static SpriteSheet terrain = new SpriteSheet("/textures/terrain.png", 96);
public SpriteSheet(String path, int size) {
this.path = path;
SIZE = size;
pixels = new int[SIZE * SIZE];
load();
}
private void load() {
try {
BufferedImage image = ImageIO.read(SpriteSheet.class.getResource(path));
int w = image.getWidth();
int h = image.getHeight();
image.getRGB(0, 0, w, h, pixels, 0, w);
} catch (IOException e) {
e.printStackTrace();
}
}
}
graphics/Screen.java :
package com.santec.game.learning.thecherno.graphics;
import java.util.Random;
public class Screen {
private int width, height;
public int[] pixels;
public final int MAP_SIZE = 8;
public final int MAP_SIZE_MASK = MAP_SIZE - 1;
public int[] tiles = new int[MAP_SIZE * MAP_SIZE];
private Random random = new Random();
public Screen(int width, int height) {
this.width = width;
this.height = height;
pixels = new int[width * height];
for(int i = 0; i < MAP_SIZE * MAP_SIZE; i++) {
tiles[i] = random.nextInt(0xffffff);
tiles[0] = 0;
}
}
public void clear() {
for(int i = 0; i < pixels.length; i++) {
pixels[i] = 0;
}
}
public void render(int xOffset, int yOffset) {
for(int y = 0; y < height; y++) {
int yy = y + yOffset;
if(yy >= height || yy < 0) break;
for(int x = 0; x < width; x++) {
int xx = x + xOffset;
if(xx >= width || xx < 0) break;
int tileIndex = ((xx >> 4) & MAP_SIZE_MASK) + ((yy >> 4) & MAP_SIZE_MASK) * 8;
pixels[x + y * width] = Sprite.grass.pixels[(xx & 15) + (yy & 15) * Sprite.grass.SIZE];
}
}
}
}
graphics/Sprite.java :
package com.santec.game.learning.thecherno.graphics;
public class Sprite {
public final int SIZE;
private int x, y;
public int[] pixels;
private SpriteSheet sheet;
public static Sprite grass = new Sprite(16, 0, 1, SpriteSheet.terrain);
public Sprite(int size, int x, int y, SpriteSheet sheet) {
SIZE = size;
this.x = x * size;
this.y = y * size;
this.sheet = sheet;
load();
}
private void load() {
for(int y = 0; y < SIZE; y++) {
for(int x = 0; x < SIZE; x++) {
pixels[x + y * SIZE] = sheet.pixels[(x + this.x) + (y + this.y) * sheet.SIZE];
}
}
}
}

You never initialize the pixels array.
add
this.pixels = new int[SIZE*SIZE]; // assuming that's the desired length or that array
to the start of your load method.

Null pointer exception despite done right

I recently was coding but encountered an null pointer exception
the stack trace says
Exception in thread "main" java.lang.NullPointerException
at com.masterkgames.twisteddream.level.SpawnLevel.generateLevel(SpawnLevel.java:34)
at com.masterkgames.twisteddream.level.Level.<init>(Level.java:22)
at com.masterkgames.twisteddream.level.SpawnLevel.<init>(SpawnLevel.java:16)
at com.masterkgames.twisteddream.Game.<init>(Game.java:49)
at com.masterkgames.twisteddream.Game.main(Game.java:138)
below are the 3 mentioned classes
Spawnlevel.java:
package com.masterkgames.twisteddream.level;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import com.masterkgames.twisteddream.level.tile.Tile;
public class SpawnLevel extends Level {
private Tile[] tiles;
private int[] levelPixels;
public SpawnLevel(String path) {
super(path);
}
protected void loadLevel(String path){
try{
BufferedImage image = ImageIO.read(SpawnLevel.class.getResource(path));
int w = image.getWidth();
int h = image.getHeight();
tiles = new Tile[w * h];
levelPixels = new int[w * h];
image.getRGB(0,0,w,h,levelPixels,0,w);
}catch(IOException e){
e.printStackTrace();
}
}
protected void generateLevel(){
for(int i = 0; i < levelPixels.length; i++){
if(levelPixels[i] == 0xff00) tiles[i] = Tile.Grass;
if(levelPixels[i] == 0xffff00) tiles[i] = Tile.Rose;
if(levelPixels[i] == 0x7f7f00) tiles[i] = Tile.Stone;
}
}
}
level.java:
package com.masterkgames.twisteddream.level;
import com.masterkgames.twisteddream.graphics.Screen;
import com.masterkgames.twisteddream.level.tile.Tile;
public class Level {
public Screen screen;
protected int width, height;
protected Tile[] tiles;
protected int[] tilesInt;
public Level(int width, int height) {
this.width = width;
this.height = height;
tilesInt = new int[width * height];
generateLevel();
}
public Level(String path) {
loadLevel(path);
generateLevel();
}
protected void generateLevel() {
}
private void loadLevel(String path) {
}
public void update() {
}
private void time() {
}
public void render(int xScroll, int yScroll, Screen screen) {
screen.setOffset(xScroll, yScroll);
int x0 = xScroll >> 4;
int x1 = (xScroll + screen.width + 16) >> 4;
int y0 = yScroll >> 4;
int y1 = (yScroll + screen.height + 16) >> 4;
for (int y = y0; y < y1; y++) {
for (int x = x0; x < x1; x++) {
// getTile(x, y).render(x, y, screen);
if (x + y * 16 < 0 || x + y * 16 >= 256) {
Tile.Void.render(x, y, screen);
continue;
}
tiles[x + y * 16].render(x, y, screen);
}
}
}
public Tile getTile(int x, int y) {
if (x < 0 || y < 0)
return Tile.Void;
if (x >= width || y >= height)
return Tile.Void;
if (tilesInt[x + y * width] == 0)
return Tile.Grass;
if (tilesInt[x + y * width] == 1)
return Tile.Rose;
if (tilesInt[x + y * width] == 2)
return Tile.Stone;
return Tile.Void;
}
}
and lastly
game.java:
package com.masterkgames.twisteddream;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import javax.swing.JFrame;
import com.masterkgames.twisteddream.entity.mob.Player;
import com.masterkgames.twisteddream.graphics.Screen;
import com.masterkgames.twisteddream.input.Keyboard;
import com.masterkgames.twisteddream.level.Level;
import com.masterkgames.twisteddream.level.SpawnLevel;
public class Game extends Canvas implements Runnable {
private static final long serialVersionUID = 1L;
public static int width = 300;
public static int height = 168;
public static int scale = 3;
public String Title = "Twisted Dream";
private Thread thread;
private boolean running = false;
private Screen screen;
private Keyboard key;
private Level level;
private Player player;
private JFrame frame;
private BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
private int[] pixels = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();
public Game() {
Dimension size = new Dimension(width * scale, height * scale);
setPreferredSize(size);
screen = new Screen(width,height);
key = new Keyboard();
level = new SpawnLevel("/textures/level.png");
player = new Player(key);
frame = new JFrame();
addKeyListener(key);
}
public synchronized void start() {
thread = new Thread(this, "Display");
thread.start();
running = true;
}
public synchronized void stop() {
running = false;
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public void run() {
long lastTime = System.nanoTime();
long timer = System.currentTimeMillis();
final double ns = 1000000000.0 / 60.0;
double delta = 0;
int frames = 0;
int updates = 0;
requestFocus();
while (running) {
long nowTime = System.nanoTime();
delta += (nowTime - lastTime) / ns;
lastTime = nowTime;
while (delta >= 1){
update();
updates++;
delta--;
}
render();
frames++;
if(System.currentTimeMillis() - timer > 1000){
timer += 1000;
System.out.println(updates + " ups, " + frames + " fps");
frame.setTitle(Title + " | " + updates + " ups, " + frames + " fps");
updates = 0;
frames = 0;
}
}
stop();
}
public void update() {
key.update();
player.update();
}
public void render() {
BufferStrategy bs = getBufferStrategy();
if (bs == null) {
createBufferStrategy(3);
return;
}
screen.clear();
int xScroll = player.x - screen.width / 2;
int yScroll = player.y - screen.height / 2;
level.render(xScroll, yScroll, screen);
player.render(screen);
for(int i = 0; i < pixels.length; i++){
pixels[i] = screen.pixels[i];
}
Graphics g = bs.getDrawGraphics();
g.drawImage(image,0,0,getWidth(),getHeight(),null);
g.setFont(new Font("arial", 0, 15));
g.setColor(Color.white);
g.dispose();
bs.show();
}
public static void main(String[] args) {
Game game = new Game();
game.frame.setResizable(false);
game.frame.setTitle(game.Title);
game.frame.add(game);
game.frame.pack();
game.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
game.frame.setLocationRelativeTo(null);
game.frame.setVisible(true);
game.start();
}
}
p.s this issue according to the stack trace is in the line for(int i = 0; i < levelPixels.length; i++) in SpawnLevel.java

in Level contructor you have generateLevel(); where you are using levelPixels, which is not initialized
contructor call
private void loadLevel(String path) {
}
from class Level, you have to call method loadLevel in SpawnLevel constructor

You are accessing the null array levelPixels.
Here is where your error is:
In your main you call a new SpawnLevel(path)
But SpawnLevel(path) calls the super constructor, which calls its blank yet defined loadLevel and generateLevel. The loadLevel and generateLevel in SpawnLevel are never called, and the member variables are never initialized.
So basically, you tried to use the Level class as an abstract class but you didnt do it correctly. The member variables should be in the Level class if they are to be shared by children of that class. Im guessing this is what you want to do.
you should really get familiar with the debugger, it will be a lifesaver for little problems like this.