fromMillisecondsSinceEpoch method
毫秒时间戳转换 DateTime
Implementation
DateTime? fromMillisecondsSinceEpoch({bool isUtc = false}) {
num n = this;
if (n is! int) n = n.toInt();
if (n.toString().length != 13) return null;
return DateTime.fromMillisecondsSinceEpoch(n, isUtc: isUtc);
}