Hello GLCube - Error CS0246: The type or namespace name 'OpenTK'

Hello to everybody,

I'm a noob, so I have a many problem for the first project. I do the example GLCube, follow: http://docs.xamarin.com/guides/android/getting_started/hello__glcube

and in the code:

using System;
using System.Runtime.InteropServices;

using OpenTK;
using OpenTK.Graphics;
using OpenTK.Graphics.ES11;
using OpenTK.Platform;
using OpenTK.Platform.Android;

using Android.Views;
using Android.Util;
using Android.Content;

namespace Mono.Samples.GLCube {

    class PaintingView : AndroidGameView
    {
        float [] rot;
        float [] rateOfRotationPS;//degrees
        int viewportWidth, viewportHeight;

        public PaintingView (Context context, IAttributeSet attrs) :
            base (context, attrs)
        {
            Initialize ();
        }

        public PaintingView (IntPtr handle, Android.Runtime.JniHandleOwnership transfer)
            : base (handle, transfer)
        {
            Initialize ();
        }

        private void Initialize ()
        {
            rateOfRotationPS = new float [] { 30, 45, 60 };
            rot = new float [] { 0, 0, 0};
        }

        // This method is called everytime the context needs
        // to be recreated. Use it to set any egl-specific settings
        // prior to context creation
        protected override void CreateFrameBuffer ()
        {
            GLContextVersion = GLContextVersion.Gles1_1;

            // the default GraphicsMode that is set consists of (16, 16, 0, 0, 2, false)
            try {
                Log.Verbose ("GLCube", "Loading with default settings");

                // if you don't call this, the context won't be created
                base.CreateFrameBuffer ();
                return;
            } catch (Exception ex) {
                Log.Verbose ("GLCube", "{0}", ex);
            }

            // this is a graphics setting that sets everything to the lowest mode possible so
            // the device returns a reliable graphics setting.
            try {
                Log.Verbose ("GLCube", "Loading with custom Android settings (low mode)");
                GraphicsMode = new AndroidGraphicsMode (0, 0, 0, 0, 0, false);

                // if you don't call this, the context won't be created
                base.CreateFrameBuffer ();
                return;
            } catch (Exception ex) {
                Log.Verbose ("GLCube", "{0}", ex);
            }
            throw new Exception ("Can't load egl, aborting");
        }


        // This gets called when the drawing surface is ready
        protected override void OnLoad (EventArgs e)
        {
            // this call is optional, and meant to raise delegates
            // in case any are registered
            base.OnLoad (e);

            // UpdateFrame and RenderFrame are called
            // by the render loop. This is takes effect
            // when we use 'Run ()', like below
            UpdateFrame += delegate (object sender, FrameEventArgs args) {
                // Rotate at a constant speed
                for (int i = 0; i < 3; i ++)
                    rot [i] += (float) (rateOfRotationPS [i] * args.Time);
            };

            RenderFrame += delegate {
                RenderCube ();
            };

            GL.Enable(All.CullFace);
            GL.ShadeModel(All.Smooth);

            GL.Hint(All.PerspectiveCorrectionHint, All.Nicest);

            // Run the render loop
            Run (30);
        }

        // this occurs mostly on rotation.
        protected override void OnResize (EventArgs e)
        {
            viewportWidth = Width;
            viewportHeight = Height;
        }

        void RenderCube ()
        {
            GL.Viewport(0, 0, viewportWidth, viewportHeight);

            GL.MatrixMode (All.Projection);
            GL.LoadIdentity ();

            if ( viewportWidth > viewportHeight )
            {
                GL.Ortho(-1.5f, 1.5f, 1.0f, -1.0f, -1.0f, 1.0f);
            }
            else
            {
                GL.Ortho(-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 1.0f);
            }

            GL.MatrixMode (All.Modelview);
            GL.LoadIdentity ();
            GL.Rotate (rot[0], 1.0f, 0.0f, 0.0f);
            GL.Rotate (rot[1], 0.0f, 1.0f, 0.0f);
            GL.Rotate (rot[2], 0.0f, 1.0f, 0.0f);

            GL.ClearColor (0, 0, 0, 1.0f);
            GL.Clear ((uint) All.ColorBufferBit);

            GL.VertexPointer(3, All.Float, 0, cube);
            GL.EnableClientState (All.VertexArray);
            GL.ColorPointer (4, All.Float, 0, cubeColors);
            GL.EnableClientState (All.ColorArray);
            GL.DrawElements(All.Triangles, 36, All.UnsignedByte, triangles);

            SwapBuffers ();
        }

        float[] cube = {
            -0.5f, 0.5f, 0.5f, // vertex[0]
            0.5f, 0.5f, 0.5f, // vertex[1]
            0.5f, -0.5f, 0.5f, // vertex[2]
            -0.5f, -0.5f, 0.5f, // vertex[3]
            -0.5f, 0.5f, -0.5f, // vertex[4]
            0.5f, 0.5f, -0.5f, // vertex[5]
            0.5f, -0.5f, -0.5f, // vertex[6]
            -0.5f, -0.5f, -0.5f, // vertex[7]
        };

        byte[] triangles = {
            1, 0, 2, // front
            3, 2, 0,
            6, 4, 5, // back
            4, 6, 7,
            4, 7, 0, // left
            7, 3, 0,
            1, 2, 5, //right
            2, 6, 5,
            0, 1, 5, // top
            0, 5, 4,
            2, 3, 6, // bottom
            3, 7, 6,
        };

        float[] cubeColors = {
            1.0f, 0.0f, 0.0f, 1.0f,
            0.0f, 1.0f, 0.0f, 1.0f,
            0.0f, 0.0f, 1.0f, 1.0f,
            0.0f, 1.0f, 1.0f, 1.0f,
            1.0f, 0.0f, 0.0f, 1.0f,
            0.0f, 1.0f, 0.0f, 1.0f,
            0.0f, 0.0f, 1.0f, 1.0f,
            0.0f, 1.0f, 1.0f, 1.0f,
        };
    }
}

in debug, have a problem: Error CS0246: The type or namespace name 'OpenTK'; probably missing a using directive or an assembly reference (CS0246) (GLCube).

The note: Since PaintingView is being created via the XML file, PaintingView must provide a public constructor accepting an System.IntPtr instance, which refers to the native proxy for the PaintingView type. I have a xml code as:

<?xml version="1.0" encoding="utf-8"?>



    
    

So the problem is that the PaitingView not accept an System.IntPtr instance?