Java LWJGL 3 Exception

[Tornation]

As a project I am trying to make a really simple engine using lwjgl 3. What I have written so far should just display a blank window running on a separate thread when started. But instead a window opens for a fraction of a second then I get a nullpointer exception in thread 0. Although I don't know much about java I find this a bit odd as all of my lwjgl code is written to run on a separate thread (usually ends up being thread 8). If possible I want to keep the graphics side of things on a separate thread.

 

The error:

Exception in thread "Thread-0" java.lang.NullPointerException
	at org.lwjgl.system.Checks.checkPointer(Checks.java:100)
	at org.lwjgl.glfw.GLFW.glfwSwapBuffers(GLFW.java:2857)
	at tungsten.graphics.Window.run(Window.java:40)
	at java.lang.Thread.run(Thread.java:745)

The app contains three files:

Game.java:

package TestGame;

import engine.application.App;

public class Game extends App {
	
	public static void main(String[] args) {
		new Game().start("Test", 800, 600);
	}
	
}

App.java:

package engine.application;

import engine.graphics.Window;

public class App {
	
	public boolean running = false;
	
	private String title;
	private Window window;
	private Thread windowThread;
	
	public void start(String title, int width, int height) {
		running = true;
		window = new Window(this, title, width, height);
		windowThread = new Thread(window);
		windowThread.start();
	}
	
	public String getTitle() {
		return title;
	}
	
}

Window.java:

package engine.graphics;

import static org.lwjgl.glfw.GLFW.*;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.system.MemoryUtil.*;

import org.lwjgl.glfw.GLFWVidMode;
import org.lwjgl.opengl.GL;

import engine.application.App;

public class Window implements Runnable {
	
	private App app;
	private String title;
	private int width;
	private int height;
	private long windowID;
	
	public Window(App app, String title, int width, int height) {
		this.app = app;
		this.title = title;
		this.width = width;
		this.height = height;
	}
	
	public void render() {
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	}
	
	@Override
	public void run() {
		init();
		
		glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
		
		while (app.running) {
			render();
			
			glfwSwapBuffers(windowID);
			glfwPollEvents();
			
			if (glfwWindowShouldClose(windowID) == GL_TRUE) {
				app.running = false;
			}
		}
	}
	
	private void init() {
		if (glfwInit() != GL_TRUE) {
		    System.err.println("ERROR: COULD NOT INIT GLFW");
		    System.exit(1);
		}
		
		long windowID = glfwCreateWindow(width, height, title, NULL, NULL);
		if (windowID == NULL) {
		    System.err.println("ERROR: COULD NOT CREATE WINDOW");
		    System.exit(1);
		}
		
		GLFWVidMode vidmode = glfwGetVideoMode(glfwGetPrimaryMonitor());
                glfwSetWindowPos(
                  windowID,
                  (vidmode.width() - width) / 2,
                  (vidmode.height() - height) / 2
                );
		
        	glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
		
		glfwMakeContextCurrent(windowID);
		glfwSwapInterval(1);
		glfwShowWindow(windowID);
		GL.createCapabilities();
	}
}

 

[fizzlesticks]

You're creating a new variable inside init called windowID instead of using your instance variable. So when you pass the windowID to swapbuffers, the variable hasn't been initialized.

[Fetzie]

The first thing I'd do is look at

GLFW.java:2857

 

and

Checks.java:100

 

to see what could be null.

 

If I couldn't see it at a first glance, I'd put a break point there and step over/into until I got to that point, and see what the debugger tells me the values are.

			glfwSwapBuffers(windowID);

is line 40 according to notepad++

 

Is your windowID null, by any chance?

[Tornation]

1 minute ago, fizzlesticks said:

You're creating a new variable inside init called windowID instead of using your instance variable. So when you pass the windowID to swapbuffers, the variable hasn't been initialized.

Herp derp thank you kind sir.