每点击一次触发更改一次材质

using UnityEngine;
using System.Collections;

public class CubeScript : MonoBehaviour {
public Material Material01;
public Material Material02;
public Material Material03;
public Material Material04;
private Material currentMaterial ;
int i = 0;
private Renderer rend;
// Use this for initialization
void Start () {

    Debug.Log(111);
   // currentMaterial = Material01;
    rend = GetComponent<Renderer>();
    rend.material = Material01;
}

// Update is called once per frame
void Update () {
    
    if (Input.GetKeyDown(KeyCode.Joystick1Button0))
    {
        i ++ ;
        Debug.Log(333);
        if (i == 1)
        {
            
            rend.material = Material02;
           // i ++;
            Debug.Log(444);
           // currentMaterial = Material02;
        }

        if (i == 2)
        {

            Debug.Log(444);
            rend.material = Material03;
            //currentMaterial = Material03;
        }
        if (i == 3)
        {
            rend.material = Material04;
            i = 0;
        }
    }
    
}

}