Adding InputHandler to game throws a java.lang.nullPointerException

[Wilson Cash]

Hi!

I have a game, and I just added a InputHandler class. The problem is that whenever I run my game, I get a java.lang.nullPointerException in my Player class where the if statement for checking if the key is pressed.

Game

import java.awt.Canvas;
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 adam.miszczak.darkrun.entity.Coin;
import adam.miszczak.darkrun.entity.ObstacleHole;
import adam.miszczak.darkrun.entity.ObstacleWolf;
import adam.miszczak.darkrun.entity.Player;
import adam.miszczak.darkrun.gfx.Screen;

public class Game extends Canvas implements Runnable{

	private static final long serialVersionUID = 1L;
	public static final int WIDTH = 350;
	public static final int HEIGHT = WIDTH / 16 * 9;
	public static final int SCALE = 2;
	
	private Thread thread;
	private JFrame frame;
	private boolean running = false;
	
	private Screen screen;
	
	private BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
	private int[] pixels = ((DataBufferInt)image.getRaster().getDataBuffer()).getData();
	
	Player player = new Player(null);
	ObstacleWolf obstacleWolf = new ObstacleWolf();
	ObstacleHole obstacleHole = new ObstacleHole();
	Coin coin = new Coin();
	public InputHandler input;
	
	public Game() {
		Dimension size = new Dimension(WIDTH * SCALE, HEIGHT * SCALE);
		setPreferredSize(size);
		
		screen = new Screen(WIDTH, HEIGHT);
		frame = new JFrame();
	}
	
	public synchronized void start() {
		running = true;
		thread = new Thread(this, "Display");
		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 ticks = 0;
		
		while(running){
			long now = System.nanoTime();
			delta += (now - lastTime) / ns;
			lastTime = now;
			
			while(delta >= 1){
				tick();
				ticks++;
				delta--;
			}
			render();
			frames++;
			
			if(System.currentTimeMillis() - timer > 1000){
				timer += 1000;
				System.out.println(ticks + " tps, " + frames + " fps");
				ticks = 0;
				frames = 0;
			}
		}
		stop();
	}
	
	public void tick(){
		player.tick();
		player.move();
		obstacleHole.move();
		obstacleWolf.move();
		coin.move();
	}
	
	public void render(){
		BufferStrategy bs = getBufferStrategy();
		if(bs == null){
			createBufferStrategy(3);
			return;
		}
		
		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);
		
		player.render(g);
		obstacleHole.render(g);
		obstacleWolf.render(g);
		coin.render(g);
		
		g.dispose();
		bs.show();
	}
	
	public static void main(String[] args){
		Game game = new Game();
		game.frame.setResizable(false);
		game.frame.setTitle("Darkrun");
		game.frame.add(game);
		game.frame.pack();
		game.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		game.frame.setLocationRelativeTo(null);
		game.frame.setVisible(true);
		
		game.start();
	}
}

InputHandler

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import java.util.List;

public class InputHandler implements KeyListener{

	public InputHandler(Game game){
		game.addKeyListener(this);
	}
	
	public class Key{
		private boolean pressed = false;
		private int numTimesPressed = 0;
		
		public int getNumTimesPressed(){
			return numTimesPressed;
		}
		
		public boolean isPressed(){
			return pressed;
		}
		
		public void toggle(boolean isPressed){
			pressed = isPressed;
			if(pressed)numTimesPressed++;
		}
	}
	
	public List<Key> keys = new ArrayList<Key>();
	
	public Key up = new Key();
	public Key down = new Key();
	public Key left = new Key();
	public Key right = new Key();
	
	public void keyPressed(KeyEvent e) {
		toggleKey(e.getKeyCode(), true);
	}

	
	public void keyReleased(KeyEvent e) {
		toggleKey(e.getKeyCode(), false);
	}

	
	public void keyTyped(KeyEvent e) {
		
		
	}
	
	public void toggleKey(int keyCode, boolean isPressed){
		if(keyCode == KeyEvent.VK_UP){up.toggle(isPressed);}
	}

}

Player

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import adam.miszczak.darkrun.InputHandler;

public class Player {
	int x;
	int y;
	int dx;
	public long xElapsed = 0;
	public int dy;
	int width = 50;
	int height = 75;
	int hangTime = 0;
	int maxHangTime = 100;
	public double playerSpeed = 0.3;
	public int coinsCollected = 0;
	public boolean isMoving = true;
	public boolean hasJumped = false;
	public boolean jumpReady = true;
	public boolean hasCollided = false;
	private BufferedImage moving1 = null;
	private InputHandler input;
	
	public Player(InputHandler input){
		try {
			moving1 = ImageIO.read(new File("res/player_moving_1.png"));
		}catch (IOException e) {
			e.printStackTrace();
		}
	
		x = 150;
		y = 250;
		
		this.input = input;
	}
	
	public void render(Graphics g){
		 Graphics2D g2d = (Graphics2D) g;
		 g2d.drawImage(moving1, x, y, null);
	}

	public void move(){
		x = x + dx;
		y = y + dy;
	
		xElapsed++;
		
		if(hasJumped == true){
			dy = 1;
			hangTime++;
		}
		
		if(hangTime == maxHangTime){
			dy = -1;
		}
		
		if(y == 150){
			dy = 0;
			hasJumped = false;
			jumpReady = true;
		}
	}
	
	public void tick(){
		if(jumpReady){
			if(input.up.isPressed()){
				hasJumped = true;
				jumpReady = false;
			}
		}
	}

	public void paint(Graphics g){
		g.setColor(Color.RED);
		g.fillRect(x, y, width, height);
	}

	public int getX(){
		return x;
	}

	public int getY(){
		return y;
	}	

	public long getXElapsed(){
		return xElapsed;
	}

	public double getSpeed(){
		return playerSpeed;
	}

	public int getCoinsCollected(){
		return coinsCollected;
	}

	public Rectangle bounds(){
		return (new Rectangle(x, y, width, height));
		}
	}

I have tried lots of things but I just cannot figure this out. It's probably something that I just overlooked and can't find. Help is appreciated. Thanks!

This is the error message:

Exception in thread "Display" java.lang.NullPointerException
	at adam.miszczak.darkrun.entity.Player.tick(Player.java:76)
	at adam.miszczak.darkrun.Game.tick(Game.java:95)
	at adam.miszczak.darkrun.Game.run(Game.java:77)
	at java.lang.Thread.run(Unknown Source)

[fred rosenberger]

I don't see where you ever create an InputHandler.

[Wilson Cash]

I'm not really sure what you mean by creating it? I have an InputHandler class.

[fred rosenberger]

Yes, you have the class defined...but that's like saying "I drafted the blueprint..what do you mean I don't have a house?". Unless you create an InputHandler object, you don't have one. You need to call it's constructor.

Put it another way...what do you think your variable 'input' holds? You declare it:

public InputHandler input;

you pass it to your player class:

public Player(InputHandler input){

you assign it to a another variable named input:

this.input = input; 

and you try to use it:

if(input.up.isPressed()){ 

Where do you assign it a value?

[Wilson Cash]

Ok I understand now. Thanks!