方法一:

using UnityEngine;
using UnityEngine.UI;

public class TimeUpdatation : MonoBehaviour
{
    /// Way 2
    int hour;
    int minute;
    int second;
    int millisecond;
    bool shouldCount = false;

    float timeSpent = 0.0f;



    void OnEnable()
    {
        shouldCount = true;
    }

    void Update()
    {
        if (shouldCount)
        {
            timeSpent += Time.deltaTime;

            hour = (int)timeSpent / 3600;
            minute = ((int)timeSpent - hour * 3600) / 60;
            second = (int)timeSpent - hour * 3600 - minute * 60;
            millisecond = (int)((timeSpent - (int)timeSpent) * 1000);

            //text_timeSpent.text = string.Format("{0:D2}:{1:D2}:{2:D2}.{3:D3}", hour, minute, second, millisecond);
            GetComponent<Text>().text = string.Format("{0:D2}:{1:D2}:{2:D2}.{3:D3}", hour, minute, second, millisecond);
        }
    }

    //void OnDestroy
    void OnDisable()
    {
        shouldCount = false;
        GetComponent<Text>().text = "";
    }
}

方法二:

using UnityEngine;
using UnityEngine.UI;

public class TimeUpdatation : MonoBehaviour
{
    /// Way 1
    public int frameRate = 30;

    void Update()
    {
        var t = Time.unscaledTime;
        var seconds = (int)t;
        var h = seconds / 3600;
        var hInSec = h * 3600;
        var m = (seconds - hInSec) / 60;
        var mInSec = m * 60;
        var s = (seconds - (hInSec + mInSec));
        var framesDouble = frameRate * (t - (double)seconds);
        var f = (int)framesDouble;
        //var frac = 100 * (framesDouble - f) / frameRate;
        GetComponent<Text>().text = $"{h:00}:{m:00}:{s:00}:{f:00}";
    }
}

作者:艾孜尔江