public class Skill : MonoBehaviour {
    //冷却时间
    public float ColdTime = 2f;
    //计时器
    float timer = 0;
    //是否开始冷却
    bool startTimer = false;
    //冷却图片
    private Image fillImage;
    void Start () {
        //获得冷却图片
        fillImage = transform.Find("FillImage").GetComponent<Image>();
    }

    void Update () {
        if (startTimer)
        {
            timer += Time.deltaTime;
            //设置冷却图片显示比率
            fillImage.fillAmount = (ColdTime - timer) / ColdTime;
            if(timer>=ColdTime)
            {
                fillImage.fillAmount = 0;
                timer = 0;
                startTimer = false;
            }
        }
    }

    public void OnReleaseSkillClickListener()
    {
        //点击按钮开始冷却
        startTimer = true;
    }
}