CODEWITHSUNDEEP
javaswingnullpointerexceptionjogl
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TrespassersW

Reputation: 413

NullPointerException in simple JOGL test case

I'm trying a very simple JOGL tutorial using NetBeans and Swing and it seems no matter how I arrange things I keep getting a null pointer exception. Here is the code I am using (adapted from a tutorial):

package testjogl;

import com.jogamp.opengl.*;
import com.jogamp.opengl.awt.GLCanvas;
import java.awt.Dimension;

public class OpenGLTest extends javax.swing.JFrame implements GLEventListener {

    public OpenGLTest() {
        initComponents();        
    }

    public void doMain() {
        GLCanvas canvas = new GLCanvas();
        canvas.addGLEventListener(this);
        canvas.setPreferredSize(new Dimension(640, 480));
        this.getContentPane().add(canvas);  // <--- This is where the exception happens
        this.pack();
        this.setVisible(true);
    }

    @Override
    public void init(GLAutoDrawable drawable) {
        GL2 gl = drawable.getGL().getGL2();      
        gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f); 
    }

    @Override
    public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) { }

    @Override
    public void display(GLAutoDrawable drawable) {
        GL2 gl = drawable.getGL().getGL2();  
        gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT); 
        gl.glLoadIdentity();  
    }

    @Override
    public void dispose(GLAutoDrawable drawable) { }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>                        

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new OpenGLTest().doMain(); 
            }
        });
    }

    // Variables declaration - do not modify                     
    // End of variables declaration                   
}

At the line where I add the canvas to my form, I get: Exception java.lang.NullPointerException(null) breakpoint hit in sun.awt.image.OffScreenImageSource at line 189 by thread AWT-EventQueue-0.

I've tried several different JOGL tutorials and all of them keep throwing this exception when I add the canvas to my form. I couldn't find the code to OffScreenImageSource, but when I step through, it dies at line 1119 in Container.java. The code is:

invalidateIfValid();
if (peer != null) {
    comp.addNotify();  // <---- Dies right here
}

Does anyone have any ideas as to what might be causing this?

Upvotes: 1

Views: 320

Answers (1)

Guillaume F.
Guillaume F.

Reputation: 6473

Your problem is you don't give enough time for Swing to initialize the component correctly with the OS GDI: As soon as you create the OpenGLTest() instance, you call doMain(). Give Swing some breath and it should work.

public static void main(String args[]) {
    OpenGLTest test;
    java.awt.EventQueue.invokeLater(() -> {
        test = new OpenGLTest()
    });
    java.awt.EventQueue.invokeLater(() -> {
        test.doMain(); 
    });
}

FYI, I didn't validate the syntax.

Upvotes: 2

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