Virtual button trigger animation

Hello all,

I have a question about virtual buttons. I want to start an animation on my cube object.

Now I have this script:

using UnityEngine;

using System.Collections;

public class VirtualButtonHandler : MonoBehaviour, IVirtualButtonEventHandler{

    private GameObject cube;

// Use this for initialization

void Start () {

// Register with the virtual buttons TrackableBehaviour

        VirtualButtonBehaviour[] vbs = GetComponentsInChildren<VirtualButtonBehaviour>();

        for (int i = 0; i < vbs.Length; ++i)

        {

            vbs[i].RegisterEventHandler(this);

        }

        // Get handle to the teapot object

        cube = GameObject.Find("cube").gameObject;

}

    // Called when the virtual button has just been pressed:

    public void OnButtonPressed(VirtualButtonBehaviour vb)

    {

        Debug.Log("OnButtonPressed");

        // Add the material corresponding to this virtual button

        // to the active material list:

        switch (vb.VirtualButtonName)

        {

            case "green":

                cube.animation.Play("Rotate180Degrees");

cube.animation.wrapMode = WrapMode.Once;

            break;

        }

    }

    // Called when the virtual button has just been released:

    public void OnButtonReleased(VirtualButtonBehaviour vb)

    {

        // Remove the material corresponding to this virtual button

        // from the active material list:

        switch (vb.VirtualButtonName)

        {

            case "green":

                //mActiveMaterials.Remove(m_TeapotMaterials[3]);

                break;

        }

    }

}

And dragged it onto the virtual button.

When I test the app the cube is displayed but the animation is not triggered when I push the virtual button.

Did I forget something or is the script not correct?

Thanks in advise.