使用 TimeSpan 类进行
void OnChangetheText(int currenttime)
{
timetext.text = currenttime.ToString();
TimeSpan span = new TimeSpan(0,0,currenttime);
timetext.text = (int)span.TotalHours + ":" + (int)span.TotalMinutes + ":" + (int)span.Seconds + "";
//Debug.Log(currenttime);
}