RectTransformUtility.ScreenPointToLocalPointInRectangleではまった

EyeStone.cs

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace EscapeRoom.LogicImplement
{
    public class EyeStone : Selectable ,IDragHandler
    {
        public Item Item;

        private bool _canDrag = false;
        private RectTransform _transform;

        private void Start()
        {
            _transform = GetComponent<RectTransform>();
        }

        public override void OnPointerUp(PointerEventData eventData)
        {
            _canDrag = false;
        }
        public override void OnPointerEnter(PointerEventData eventData)
        {
            _canDrag = true;
        }
        public override void OnPointerExit(PointerEventData eventData)
        {
            _canDrag = false;
        }

        public void OnDrag(PointerEventData eventData)
        {
            Vector2 localPos = Vector2.zero;
            var ii =RectTransformUtility.ScreenPointToLocalPointInRectangle(
               transform .parent .GetComponent<RectTransform>(),
                eventData.position,
                Camera.main,
                out localPos
            );
            _transform.localPosition = localPos;
        }
    }
}