flutter - createState 方法在 Flutter 中的 StatefulWidget 中不起作用......它显示以下错误

Question

那里 createState 方法不起作用..

[class MysignupPage extends StatefulWidget {
  const MysignupPage({ Key key }) : super(key: key);
  @override
  _MysignupPageState createState() => _MysignupPageState();
}
class _MysignupPageState extends StatelessWidget {
  final _auth = FirebaseAuth.instance;][1]

显示此错误 [1]：https ://i.stack.imgur.com/An0iV.png