在canvas初始化的时候设置渲染模式为ScreenSpaceCamera,并指定摄像机

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class CanvasInit : MonoBehaviour
{
    private void Awake()
    {
        Canvas thiscanvas = GetComponent<Canvas>();

        thiscanvas.renderMode=RenderMode.ScreenSpaceCamera;

        GameObject gameObject = GameObject.Find("Main Camera");

        thiscanvas.worldCamera = gameObject.GetComponent<Camera>();
    }
}