[Bug] Está com algum problema

Mesmo depois de ter copiado o código do professor o erro continua, segue:

import 'package:flutter/material.dart';

class FormScreen extends StatefulWidget {
  const FormScreen({super.key});

  @override
  State<FormScreen> createState() => _FormSreenState();
}

class _FormSreenState extends State<FormScreen> {
  TextEditingController nameController = TextEditingController();
  TextEditingController difficultyController = TextEditingController();
  TextEditingController imageController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Formulário'),
      ),
      body: Center(
        child: SingleChildScrollView(
          child: Container(
            height: 650,
            width: 375,
            decoration: BoxDecoration(
              color: Colors.black26,
              borderRadius: BorderRadius.circular(10),
              border: Border.all(width: 3),
            ),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              crossAxisAlignment: CrossAxisAlignment.center,
              children: [
                Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: TextFormField(
                    controller: nameController,
                    textAlign: TextAlign.center,
                    decoration: InputDecoration(
                      border: OutlineInputBorder(),
                      hintText: 'Qual seu nome?',
                      fillColor: Colors.white70,
                      filled: true,
                    ),
                  ),
                ),
                Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: TextFormField(
                    controller: difficultyController,
                    textAlign: TextAlign.center,
                    decoration: InputDecoration(
                      border: OutlineInputBorder(),
                      hintText: 'Dificuldade',
                      fillColor: Colors.white70,
                      filled: true,
                    ),
                  ),
                ),
                Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: TextFormField(
                    onChanged: (text) {
                      setState(() {});
                    },
                    controller: imageController,
                    textAlign: TextAlign.center,
                    decoration: InputDecoration(
                      border: OutlineInputBorder(),
                      hintText: 'Imagem',
                      fillColor: Colors.white70,
                      filled: true,
                    ),
                  ),
                ),
                Container(
                  height: 100,
                  width: 72,
                  decoration: BoxDecoration(
                    color: Colors.blue,
                    borderRadius: BorderRadius.circular(10),
                    border: Border.all(
                      width: 2,
                      color: Colors.blue,
                    ),
                  ),
                  child: ClipRRect(
                    borderRadius: BorderRadius.circular(10),
                    child: Image.network(
                      imageController.text,
                      errorBuilder: (BuildContext context, Object exception, StackTrace? stackTrace) {
                        return Image.asset(
                          'assets/images/nophoto.png',
                        );
                      },
                      fit: BoxFit.cover,
                    ),
                  ),
                ),
                ElevatedButton(
                  onPressed: () {
                    print(nameController.text);
                    print(int.parse(difficultyController.text));
                    print(imageController.text);
                  },
                  child: Text('Adicionar'),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}