unity3d 安卓 再按一次退出

using UnityEngine;
using System.Collections;

public class QuitCheck : MonoBehaviour
{

public UnityEngine.UI.Text tipTextBox;

public CanvasGroup canvasGroup;
public string tip = "再按一次退出应用";
int escapeTimes = 0;

void Start()
{
canvasGroup.alpha = 0f;
}
void Update()
{
if (Input.GetKeyDown(KeyCode.Escape))
{

tipTextBox.text = tip;
canvasGroup.alpha = 1f;
escapeTimes++;

StartCoroutine("resetTimes");
if (escapeTimes > 1)
{
Debug.Log("Quit!");
Application.Quit();
}
}
}
IEnumerator resetTimes()
{
yield return new WaitForSeconds(2);
escapeTimes = 0;
canvasGroup.alpha = 0f;
}

}