Sprite按钮挂载脚本函数报错，求大神帮看看

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using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class CharacterCreation : MonoBehaviour {
public GameObject[] characterPrefabs;
private GameObject[] characterGameObjects;
private int selectedIndex = 0;
private int lenght;
// Use this for initialization
void Start () {
lenght = characterPrefabs.Length;
characterGameObjects = new GameObject[lenght];
for(int i = 0;i<lenght;i++){
characterGameObjects [i] = GameObject.Instantiate (characterPrefabs [i], transform.position, transform.rotation) as GameObject;
}
UpdateCharacterShow ();
}
// Update is called once per frame
void Update () {
}
void UpdateCharacterShow(){
characterGameObjects [selectedIndex].SetActive (true);
for(int i = 0;i<lenght;i++){
if(i != selectedIndex){
characterGameObjects [i].SetActive (false);
}
}
}
public void OnNextButton(){
selectedIndex++;
selectedIndex %= lenght;
UpdateCharacterShow ();
}
public void OnPrevButton(){
selectedIndex--;
if(selectedIndex == -1){
selectedIndex = lenght - 1;
}
UpdateCharacterShow ();
}
}