Unity如何实现UI渐隐渐显效果

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
/// <summary>
/// UI的渐入渐出
/// </summary>
public class UI_FadeInFadeOut : MonoBehaviour {
 private float UI_Alpha = 1;    //初始化时让UI显示
 public float alphaSpeed = 2f;   //渐隐渐显的速度
 private CanvasGroup canvasGroup;
 
 // Use this for initialization
 void Start () {
  canvasGroup = this.GetComponent<CanvasGroup>();
 }
 
 // Update is called once per frame
 void Update () {
  if (canvasGroup == null)
  {
   return;
  }
 
  if (UI_Alpha != canvasGroup.alpha)
  {
   canvasGroup.alpha = Mathf.Lerp(canvasGroup.alpha, UI_Alpha, alphaSpeed * Time.deltaTime);
   if (Mathf.Abs(UI_Alpha - canvasGroup.alpha) <= 0.01f)
   {
    canvasGroup.alpha = UI_Alpha;
   }
  }
 }
 public void UI_FadeIn_Event()
 {
  UI_Alpha = 1;
  canvasGroup.blocksRaycasts = true;  //可以和该对象交互
 }
 public void UI_FadeOut_Event()
 {
  UI_Alpha = 0;
  canvasGroup.blocksRaycasts = false;  //不可以和该对象交互
 }
}