在Unity中除了用Slider、Image做进度条，其实用Scrollbar也可以做进度条。

首先，在场景中新建一个Scrollbar组件和一个Text组件：

其次，创建模拟进度的一个脚本，Scrollbar_Progressbar.cs:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using TMPro;

public class Scrollbar_Progressbar : MonoBehaviour
{
    public Scrollbar scrollbar;
    public TextMeshProUGUI text;

    private float curCount = 0;  //当前加载量,从0开始加载
    private float allCount = 100f;   //总加载量,这里设置为100

    private float smoothSpeed = 0.1f;  //加载的速度

    private bool changeValue;
    private bool changeSize;

    // Start is called before the first frame update
    void Start()
    {

    }

    // Update is called once per frame
    void Update()
    {
        if(Input.GetKeyDown(KeyCode.A))
        {
            changeValue = true;
            curCount = 0;
            scrollbar.size = 0;
        }
        else if(Input.GetKeyDown(KeyCode.S))
        {
            changeSize = true;
            curCount = 0;
            scrollbar.value = 0;            
        }
        if(changeValue)
        {
            if (curCount < allCount)
            {
                curCount += smoothSpeed;
                if (curCount > allCount)
                {
                    curCount = 100f;
                }
                scrollbar.value = curCount / 100f;
                text.text = (int)curCount / allCount * 100 + "%";
            }
            else
            {
                changeValue = false;
            }
        }
        if(changeSize)
        {
            if (curCount < allCount)
            {
                curCount += smoothSpeed;
                if (curCount > allCount)
                {
                    curCount = 100f;
                }
                scrollbar.size = curCount / 100f;
                text.text = (int)curCount / allCount * 100 + "%";
            }
            else
            {
                changeSize = false;
            }
        }
        
    }
}

我这里特别模拟了改变scrollbar中Value和Size属性的两种情况，经检验，只有改变Size值才符合进度条的效果。

具体效果如下：