unity3d之简单的时钟倒计时demo

输入结束时间，开始倒计时，时间差不超过一天，附上代码：(关于个位数显示，加个判断如果小于10 显示的字符串加上0)

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using System;
public class CountdownDemo : MonoBehaviour {

    public Text hour;
    public Text min;
    public Text sec;
    public InputField timestr;
    public Coroutine cc;
    private DateTime endtime;

    
    
    IEnumerator countdown()
    {
        while (true)
        {
            TimeSpan temp = endtime - DateTime.Now;
            hour.text = temp.Hours.ToString();
            min.text = temp.Minutes.ToString();
            sec.text = temp.Seconds.ToString();
            yield return new WaitForSeconds(1);
        }
    }

    void OnGUI()
    {
        if (GUI.Button(new Rect(0, 0, 100, 30), "start"))
        {
            endtime = Convert.ToDateTime(timestr.text);
            cc = StartCoroutine(countdown());
        }
        if (GUI.Button(new Rect(0, 100, 100, 30), "end"))
        {
            this.StopCoroutine(cc);
        }
    }
}