unity中实现监听鼠标的进入和退出某一个UI按钮

using UnityEngine;
using System.Collections;
using Assets.Code.myclass;
using UnityEngine.UI;
using DG.Tweening;
using UnityEngine.EventSystems;

public class ButtonEventTriggerListener : MonoBehaviour, IPointerEnterHandler, IPointerExitHandler
{
　　//单例模式
    static ButtonEventTriggerListener buttonEvent_this;
    public static ButtonEventTriggerListener Instance()
    {
        if (buttonEvent_this == null)
        {
            buttonEvent_this = new ButtonEventTriggerListener();
        }
        return buttonEvent_this;
    }
    private float origiValue;
    private float endValue = ;
    private GameObject btnBcak;
    private string mainPanelPath = "mainControllerPanel(Clone)/back/menuPanel/";
    public void Start()
    {
        btnBcak = GameObject.Find(mainPanelPath + "RoamBack").gameObject;
        origiValue = btnBcak.transform.position.x;
    }

    public void OnPointerEnter(PointerEventData eventData)
    {
        Debug.LogError("进入");
        btnBcak.transform.DOLocalMoveX(endValue, 0.5f);
    }

    public void OnPointerExit(PointerEventData eventData)
    {
        Debug.LogError("退出");
        btnBcak.transform.DOLocalMoveX(origiValue, 0.5f);
    }
}