Unity如何实现UI渐变效果

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
 
public class ToolTilePanel : MonoBehaviour
{
 private float alpha = 0.0f;
 private float alphaSpeed = 2.0f;
 
 private CanvasGroup cg;
 
 void Start ()
 { 
 cg = this.transform.GetComponent<CanvasGroup>(); 
 }
 
 void Update ()
 {
 if (alpha != cg.alpha)
 {
 cg.alpha = Mathf.Lerp(cg.alpha,alpha,alphaSpeed * Time.deltaTime);
 if (Mathf.Abs(alpha-cg.alpha)<=0.01)
 {
 cg.alpha = alpha;
 }
 }
 }
 
 public void Show()
 {
 alpha = 1;
 
 cg.blocksRaycasts = true;//可以和该UI对象交互
 }
 
 public void Hide()
 {
 alpha = 0;
 
 cg.blocksRaycasts = false;//不可以和该UI对象交互
 }