@override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Transferencia'),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          final Future<Transferencia?> future = Navigator.push(context, MaterialPageRoute(builder: (context){
            return FormularioTransferencia();
          }));
          future.then((transfRecebida) => debugPrint('Trans recebida'));
          if(transfRecebida != null) {
            _transferencias.add(transfRecebida);
            O ERRO OCORRE AQUI.
          }
        },
        child: const Icon(Icons.add),
      ),
      body: ListView.builder(
        itemCount: _transferencias.length,
        itemBuilder: (context, int indice) {
        return ItemTransferencia(_transferencias[indice]);
      },
      )
    );
  }