如何在unity3d的ScrollView中实例化完美大小的预制件？

using UnityEngine;
using UnityEngine.UI;

public class ScrollViewInstantiation : MonoBehaviour
{
    public GameObject prefab; // 预制件
    public RectTransform content; // ScrollView的Content
    public RectTransform prefabParent; // 预制件的父对象

    public int numberOfItems; // 预制件数量
    public float itemHeight; // 预制件高度

    private void Start()
    {
        // 实例化预制件
        for (int i = 0; i < numberOfItems; i++)
        {
            GameObject item = Instantiate(prefab, prefabParent);
            item.GetComponent<RectTransform>().anchoredPosition = new Vector2(0, -i * itemHeight);
        }

        // 调整Content的大小
        float contentHeight = numberOfItems * itemHeight;
        content.sizeDelta = new Vector2(content.sizeDelta.x, contentHeight);

        // 调整预制件父对象的位置
        prefabParent.anchoredPosition = new Vector2(prefabParent.anchoredPosition.x, contentHeight / 2);
    }
}