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Thread: Making A 2D Game Engine But There Is A NullPointerException From Input

  1. #1
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    Unhappy Making A 2D Game Engine But There Is A NullPointerException From Input

    Exception in thread "main" java.lang.NullPointerException: Cannot invoke "com.chara.engine.Window.getCanvas()" because the return value of "com.chara.engine.GameContainer.getWindow()" is null
    at module.chara/com.chara.engine.Input.<init>(Input.java:32)
    at module.chara/com.chara.engine.GameContainer.start(GameContainer .java:25)
    at module.chara/com.chara.engine.GameContainer.main(GameContainer. java:118)

    MainComponent.java
    package com.chara.engine;
     
    import java.awt.event.KeyEvent;
     
    public class GameContainer implements Runnable 
    {
    	private Thread thread;
    	private Window window;
    	private Renderer renderer;
    	private Input input;
     
    	private boolean running = false;
    	private final double UPDATE_CAP = 1.0/60.0;
    	private int width = 800, height = 600;
    	private float scale = 1f;
    	private String title = "Chara Engine v1.0";
     
    	public GameContainer() 
    	{
     
    	}
     
    	public void start()
    	{
    		input = new Input(this);
    		window = new Window(this);
    		renderer = new Renderer(this);
    		thread = new Thread(this);
    		thread.run();
    	}
     
    	public void stop()
    	{
     
    	}
     
    	public void run()
    	{
    		running = true;
     
    		boolean render = false;
    		float firstTime = 0;
    		float lastTime = System.nanoTime() / 1000000000f;
    		double passedTime = 0;
    		double unprocessedTime = 0;
     
    		double frameTime = 0;
    		int frames = 0;
    		int fps = 0;
     
    		while(running)
    		{
    			render = false;
     
    			firstTime = System.nanoTime() / 1000000000.0f;	
    			passedTime = firstTime - lastTime;
    			lastTime = firstTime;
     
    			unprocessedTime += passedTime;
    			frameTime += passedTime;
     
    			while(unprocessedTime >= UPDATE_CAP)
    			{
     
     
    				unprocessedTime -= UPDATE_CAP;
     
    				render = true;
     
    				if(frameTime >= 1.0) 
    				{
    					frameTime = 0;
    					fps = frames;
     
    					frames = 0;
     
    					System.out.println("FPS:"+ fps);
    				}
    				//TODO: Update game
    				if(input.isKey(KeyEvent.VK_A))
    				{
    					System.out.println("A");
    				}
     
    				input.update();
     
    			}
     
    			if(render)
    			{
    				renderer.clear();
    				window.update();
    				frames++;
    				//TODO: Render game
    			}else
    			{
    				try 
    				{
    					Thread.sleep(1);
    				} catch (InterruptedException e) 
    				{
    					e.printStackTrace();
    				}
    			}
    		}
    		dispose();
     
    	}
     
    	private void dispose()
    	{
     
    	}
     
    	public static void main(String[] args)
    	{
    		GameContainer gc = new GameContainer();
    		gc.start();
    	}
     
    	public int getWidth() {
    		return width;
    	}
     
    	public void setWidth(int width) {
    		this.width = width;
    	}
     
    	public int getHeight() {
    		return height;
    	}
     
    	public void setHeight(int height) {
    		this.height = height;
    	}
     
    	public float getScale() {
    		return scale;
    	}
     
    	public void setScale(float scale) {
    		this.scale = scale;
    	}
     
    	public String getTitle() {
    		return title;
    	}
     
    	public void setTitle(String title) {
    		this.title = title;
    	}
     
    	public Window getWindow() {
    		return window;
    	}
     
    	public Input getInput() {
    		return input;
    	}
    }

    Input.java
    package com.chara.engine;
     
    import java.awt.event.KeyEvent;
    import java.awt.event.KeyListener;
    import java.awt.event.MouseEvent;
    import java.awt.event.MouseListener;
    import java.awt.event.MouseMotionListener;
    import java.awt.event.MouseWheelEvent;
    import java.awt.event.MouseWheelListener;
     
    public class Input implements KeyListener, MouseListener, MouseMotionListener, MouseWheelListener
    {
    	private GameContainer gc;
     
    	private final int NUM_KEYS = 256;
    	private final int NUM_BUTTONS = 5;
    	private boolean[] keys = new boolean[NUM_KEYS];
    	private boolean[] keysLast = new boolean[NUM_KEYS];
    	private boolean[] buttons = new boolean[NUM_BUTTONS];
    	private boolean[] buttonsLast = new boolean[NUM_BUTTONS];
     
    	private int mouseX, mouseY;
    	private int scroll;
     
    	public Input(GameContainer gc)
    	{
    		this.gc = gc;
    		mouseX = 0;
    		mouseY = 0;
    		scroll = 0;
     
    		gc.getWindow().getCanvas().addKeyListener(this);
    		gc.getWindow().getCanvas().addMouseMotionListener(this);
    		gc.getWindow().getCanvas().addMouseListener(this);
    		gc.getWindow().getCanvas().addMouseWheelListener(this);
    	}
     
    	public void update()
    	{
    		for(int i = 0; i < NUM_KEYS; i++)
    		{
    			keysLast[i] = keys[i];
    		}
    		for(int i = 0; i < NUM_BUTTONS; i++)
    		{
    			buttonsLast[i] = buttons[i];
    		}
    	}
     
    	public boolean isKey(int keyCode)
    	{
    		return keys[keyCode];
    	}
    	public boolean isKeyUp(int keyCode)
    	{
    		return !keys[keyCode] && keysLast[keyCode];
    	}
    	public boolean isKeyDown(int keyCode)
    	{
    		return keys[keyCode] && !keysLast[keyCode];
    	}
     
    	public boolean isButton(int button)
    	{
    		return buttons[button];
    	}
    	public boolean isButtonUp(int button)
    	{
    		return !buttons[button] && buttonsLast[button];
    	}
    	public boolean isButtonDown(int button)
    	{
    		return buttons[button] && !buttonsLast[button];
    	}
     
    	@Override
    	public void mouseWheelMoved(MouseWheelEvent e) 
    	{
    		scroll = e.getWheelRotation();
    	}
     
    	@Override
    	public void mouseDragged(MouseEvent e) 
    	{
    		mouseX = (int)(e.getX() / gc.getScale());
    		mouseY = (int)(e.getY() / gc.getScale());
    	}
     
    	@Override
    	public void mouseMoved(MouseEvent e) 
    	{
    		mouseX = (int)(e.getX() / gc.getScale());
    		mouseY = (int)(e.getY() / gc.getScale());
    	}
     
    	@Override
    	public void mouseClicked(MouseEvent e) {
    		// TODO Auto-generated method stub
     
    	}
     
    	@Override
    	public void mousePressed(MouseEvent e) 
    	{
    		buttons[e.getButton()] = true;
    	}
     
    	@Override
    	public void mouseReleased(MouseEvent e) 
    	{
    		buttons[e.getButton()] = false;
    	}
     
    	@Override
    	public void mouseEntered(MouseEvent e) {
    		// TODO Auto-generated method stub
     
    	}
     
    	@Override
    	public void mouseExited(MouseEvent e) {
    		// TODO Auto-generated method stub
     
    	}
     
    	@Override
    	public void keyTyped(KeyEvent e) {
    		// TODO Auto-generated method stub
     
    	}
     
    	@Override
    	public void keyPressed(KeyEvent e) 
    	{
    		keys[e.getKeyCode()] = true;
    	}
     
    	@Override
    	public void keyReleased(KeyEvent e) 
    	{
    		keys[e.getKeyCode()] = false;
    	}
     
    	public boolean[] getKeys() {
    		return keys;
    	}
     
    	public boolean[] getButtons() {
    		return buttons;
    	}
     
    	public int getMouseX() {
    		return mouseX;
    	}
     
    	public int getMouseY() {
    		return mouseY;
    	}
     
    	public int getScroll() {
    		return scroll;
    	}
     
    }

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Making A 2D Game Engine But There Is A NullPointerException From Input

    The posted code does not compile for testing because there are missing classes.
    If you don't understand my answer, don't ignore it, ask a question.

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