Question

i try to write a code that show a rect in a blue frame:

 import java.awt.Color;
import javax.media.opengl.GL;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCanvas;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import com.sun.opengl.util.Animator;
public class Jojl extends GLCanvas implements GLEventListener {

static final long serialVersionUID = 4262202874615600756L;

public static void main(String[] args) {
    Jojl convas=new Jojl();
    Animator animator=new Animator(convas);
    JFrame jframe=new JFrame("hello JOGL");
    jframe.setVisible(true);
    jframe.setSize(500,500);
    jframe.setVisible(true);
    jframe.setLayout(null);
    JPanel jp=new JPanel();
    jp.setSize(jframe.getSize());
    jframe.add(jp);
    jp.setBackground(Color.BLUE);
    jp.add(convas);
    jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    animator.start();

    }

    public Jojl()
    {
    super( new GLCapabilities());

    }
    @Override
    public void display(GLAutoDrawable arg0) {
        System.out.println("hello");
        GL gl=arg0.getGL();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
        gl.glRectf(-0.5f,-0.5f,0.5f,0.5f);


    }

    @Override
    public void displayChanged(GLAutoDrawable arg0, boolean arg1, boolean arg2) {

    }

    @Override
    public void init(GLAutoDrawable arg0) {

    }

    @Override
    public void reshape(GLAutoDrawable arg0, int arg1, int arg2, int arg3,
            int arg4) {
        // TODO Auto-generated method stub

    }
}

but this show only a blue frame and not show rectangle.

Answer 1

Try this way:

import javax.media.opengl.GL;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCanvas;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import com.sun.opengl.util.Animator;
import java.awt.BorderLayout;

public class Jojl extends GLCanvas implements GLEventListener {

    static final long serialVersionUID = 4262202874615600756L;

    public static void main(String[] args) {
        Jojl convas = new Jojl();
        Animator animator = new Animator(convas);
        JFrame jframe = new JFrame("hello JOGL");
        jframe.setVisible(true);
        jframe.setSize(500, 500);
        jframe.setVisible(true);
        jframe.setLayout(null);
        JPanel jp = new JPanel(new BorderLayout()); // 1.              <- HERE
        jp.setSize(jframe.getSize());
        jframe.add(jp);
        // jp.setBackground(Color.BLUE); // 2. rather do that in JOGL
        jp.add(convas);
        jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        animator.start();

    }

    public Jojl() {
        super(new GLCapabilities());
        addGLEventListener(this);  // 2.                              <-- HERE
    }

    @Override
    public void display(GLAutoDrawable arg0) {
        System.out.println("hello");
        GL gl = arg0.getGL();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
        gl.glRectf(-0.5f, -0.5f, 0.5f, 0.5f);
    }

    @Override
    public void displayChanged(GLAutoDrawable arg0,
            boolean arg1, boolean arg2) {}

    @Override
    public void init(GLAutoDrawable arg0) {}

    @Override
    public void reshape(GLAutoDrawable arg0, int arg1, int arg2, int arg3,
            int arg4) {}
}

Note the comments. You missed only two elements:

• Adding GLEventListener to GLCanvas. Normally You don’t extend GLCanvas, implementing GLEventlistener is all that is required to get GL.

• JPanel’s LayoutManager was unspecified, so no care was taken to layout the canvas at full extent