Erro, versão flutter Flutter 2.6.0-5.1 e Dart 2.15.0 (build 2.15.0-82.0.dev), no momento de chamar a class

O problema.


Este é a class que criei.

class FormularioTransferencia extends StatelessWidget {
  const FormularioTransferencia({Key? key}) : super(key: key);

  final TextEditingController _controladorCampoNumeroConta =
      TextEditingController();
  final TextEditingController _controladorCampoValor = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Criando Transferência'),
      ),
      body: Column(
        children: [
          Padding(
            padding: const EdgeInsets.only(left: 8, right: 8, top: 16, bottom: 16),
            child: TextField(
              controller: _controladorCampoNumeroConta,
              style: const TextStyle(fontSize: 24),
              decoration: const InputDecoration(
                labelText: 'Número da conta',
                hintText: "0000", //um placeholde
              ),
              keyboardType: TextInputType
                  .number, //define o modelo de teclado que vai aparecer.
            ),
          ),
          Padding(
            padding: const EdgeInsets.only(left: 8, right: 8, top: 16, bottom: 16),
            child: TextField(
              controller: _controladorCampoValor,
              style: const TextStyle(fontSize: 24),
              decoration: const InputDecoration(
                icon: Icon(Icons.monetization_on),
                labelText: 'Valor',
                hintText: "0.00", //um placeholde
              ),
              keyboardType: TextInputType
                  .number, //define o modelo de teclado que vai aparecer.
            ),
          ),
          ElevatedButton(
            child: const Text("Confirmar"),
            onPressed: () {
              debugPrint("Confirmar");
              final int? numeroConta =
                  int.tryParse(_controladorCampoNumeroConta as String);
              final double? valor =
                  double.tryParse(_controladorCampoValor as String);
              if (numeroConta != null && valor != null) {
                final transferenciaCriada = Transferencia(valor, numeroConta);
                debugPrint('$transferenciaCriada');
              }
            },
          ),
        ],
      ),
    );
  }