Unity中使用协程实现倒计时功能

using UnityEngine;
using System.Collections;

public class ShowNumber : MonoBehaviour {
private int tmp = 10;
// Use this for initialization
void Start () {
//开启一个协程
StartCoroutine("changeTime");
}
void OnGUI()
{
GUILayout.BeginArea(new Rect(100,100,300,100));
GUILayout.Label("" + tmp, GUILayout.Width(300));
GUILayout.EndArea();
}

IEnumerator changeTime()
{
while(tmp > 0)
{
//暂停一秒
yield return new WaitForSeconds(1);
tmp--;
}
}
}