Flutter:无法在初始值设定项中访问实例成员“”_buildFormTextFields“”

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  late TextEditingController _controller;

  _MyWidgetState() {
    _controller = TextEditingController();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: TextField(
          controller: _controller,
          decoration: InputDecoration(
            labelText: 'Enter a value',
          ),
        ),
      ),
    );
  }
}