未找到Vuforia命名空间

我用Vuforia为增强现实制作了一个虚拟按钮：

using UnityEngine;
using System.Collections.Generic;

public class VBGordangDuaEventHandler : MonoBehaviour, IVirtualButtonEventHandler
{
    #region PUBLIC_MEMBER_VARIABLES

    /// <summary>
    /// The materials that will be set for the teapot model
    /// </summary>
    public Material[] m_TeapotMaterials;
    public AudioSource VBgordangduahitam;
    public AudioSource VBgordangduamerah;

    #endregion $3$



    #region PRIVATE_MEMBER_VARIABLES

private GameObject mTeapot;
private List<Material> mActiveMaterials;

#endregion $4$



#region UNITY_MONOBEHAVIOUR_METHODS

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
    //      mTeapot = transform.FindChild("teapot").gameObject;

    // The list of active materials
    mActiveMaterials = new List<Material>();
}

#endregion $9$



#region PUBLIC_METHODS

/// <summary>
/// Called when the virtual button has just been pressed:
/// </summary>
public void OnButtonPressed(VirtualButtonAbstractBehaviour vb)
{
    Debug.Log("OnButtonPressed::" + vb.VirtualButtonName);

    /*if (!IsValid())
    {
        return;
    }*/

    // Add the material corresponding to this virtual button
    // to the active material list:
    switch (vb.VirtualButtonName)
    {
    case "VBgordangduahitam":
        Debug.Log ("gordangduahitam");
        suaragordangduahitam.Play ();
        break;

    case "VBgordangduamerah":
        Debug.Log ("gordang2merah");
        suaragordangduamerah.Play ();
        break;

    }

    // Apply the new material:
    /*if (mActiveMaterials.Count > 0)
        mTeapot.renderer.material = mActiveMaterials[mActiveMaterials.Count - 1];*/
}


/// <summary>
/// Called when the virtual button has just been released:
/// </summary>
public void OnButtonReleased(VirtualButtonAbstractBehaviour vb)
{
    if (!IsValid())
    {
        return;
    }

    // Remove the material corresponding to this virtual button
    // from the active material list:
    switch (vb.VirtualButtonName)
    {
    case "red":
        mActiveMaterials.Remove(m_TeapotMaterials[0]);
        break;

    case "blue":
        mActiveMaterials.Remove(m_TeapotMaterials[1]);
        break;

    case "yellow":
        mActiveMaterials.Remove(m_TeapotMaterials[2]);
        break;

    case "green":
        mActiveMaterials.Remove(m_TeapotMaterials[3]);
        break;
    }

    // Apply the next active material, or apply the default material:
    /*if (mActiveMaterials.Count > 0)
        mTeapot.renderer.material = mActiveMaterials[mActiveMaterials.Count - 1];
    else
        mTeapot.renderer.material = m_TeapotMaterials[4];*/
}


private bool IsValid()
{
    // Check the materials and teapot have been set:
    return  mTeapot != null;
}

#endregion $35$

为什么会出现以下错误？

1）：错误CS0246：找不到类型或命名空间名称'IVirtualButtonEventHandler'（您是否缺少using指令或程序集引用？）（CS0246）（Assembly-CSharp）2）：错误CS0246：类型或命名空间找不到名称'VirtualButtonAbstractBehaviour'（您是否缺少using指令或程序集引用？）（CS0246）（Assembly-CSharp）3）：错误CS0246：找不到类型或命名空间名称'VirtualButtonAbstractBehaviour'（是你吗？缺少using指令或程序集引用？）（CS0246）（Assembly-CSharp）4）：错误CS0246：找不到类型或命名空间名称'VuforiaBehaviourComponentFactory'（您是否缺少using指令或程序集引用？）（ CS0246）（Assembly-CSharp-Editor）

我该如何解决这些错误？