ScrollRectのスクロールチェンジをユーザー操作以外の場合は上部固定にするやつ

ScrollController.cs

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

public class ScrollController : MonoBehaviour, IInitializePotentialDragHandler, IEndDragHandler
{
    public enum ScrollState {
        Wait,
        BeginDrag,
        EndDrag
    }
    private ScrollState state;
    
    private ScrollRect scrollRect;

    private void Awake()
    {
        this.scrollRect = gameObject.GetComponent<ScrollRect>();
        this.state = ScrollState.Wait;
    }
    
    private void Update()
    {
        if (this.state != ScrollState.EndDrag) {
            return;
        }
        // ユーザー操作が終わっても惰性でスクロールは続くので止まるまでチェッキング 
        else if (this.scrollRect.velocity.Equals(Vector2.zero)) {
            this.state = ScrollState.Wait;
        }
    }
    
    // ScrollRect value changed
    public void OnChangedScrollPosition(Vector2 position)
    {
        if (this.state == ScrollState.Wait) {
            // ユーザーによる操作じゃないので止める
            this.scrollRect.verticalNormalizedPosition = 1;
        }
    }
    
    // IInitializePotentialDragHandler
    public void OnInitializePotentialDrag(PointerEventData eventData)
    {
        this.state = ScrollState.BeginDrag;
    }
    
    // IEndDragHandler
    public void OnEndDrag(PointerEventData data)
    {
        this.state = ScrollState.EndDrag;
    }
    
}