嗨，我是新来的Flutter和使用BlueStacks作为一个AVD。我看到这个错误在BlueStacks。VS代码不显示任何错误。enter image description here
运行应用后，我在Debug Consle中看到这些消息：enter image description hereenter image description here
下面是我的main.dart代码：

import 'package:flutter/material.dart';

import './quiz.dart';
import './result.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _MyAppState();
  }
}

class _MyAppState extends State<MyApp> {
  final _questions = const [
    {
      'questionText': 'whats ur favorite animal',
      'answers': [
        {'Text': 'khar', 'score': '10'},
        {'Text': 'gaav', 'score': '7'},
        {'Text': 'asb', 'score': '1'},
        {'Text': 'boz', 'score': '3'},
      ],
    },
    {
      'questionText': 'whats ur favorite color',
      'answers': [
        {'Text': 'siah', 'score': '10'},
        {'Text': 'sabz', 'score': '3'},
        {'Text': 'sefid', 'score': '1'},
        {'Text': 'sorkh', 'score': '5'},
      ],
    },
    {
      'questionText': 'whats ur favorite name',
      'answers': [
        {'Text': 'reza', 'score': '1'},
        {'Text': 'reza', 'score': '1'},
        {'Text': 'reza', 'score': '1'},
        {'Text': 'reza', 'score': '1'}
      ],
    },
  ];
  var _questionIndex = 0;
  var _totalScore = 0;

  void _resetQuiz() {
    setState(() {
      _questionIndex = 0;
      _totalScore = 0;
    });
  }

  void _answerQuestion(int score) {
    _totalScore = _totalScore + score;

    setState(() {
      _questionIndex = _questionIndex + 1;
    });
    print(_questionIndex);
    if (_questionIndex < _questions.length) {
      print('we have more question!');
    } else {
      print('no more question!');
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('my first app'),
        ),
        body: _questionIndex < _questions.length
            ? Quiz(
                answerQuestion: _answerQuestion,
                questionIndex: _questionIndex,
                questions: _questions,
              )
            : Result(_totalScore, _resetQuiz),
      ),
    );
  }
}

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下面是我的quiz.dart文件：

import 'package:flutter/material.dart';

import './question.dart';
import './answer.dart';

class Quiz extends StatelessWidget {
  final List<Map<String, Object>> questions;
  final int questionIndex;
  final Function answerQuestion;

  Quiz(
      {required this.questions,
      required this.answerQuestion,
      required this.questionIndex});

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Question(
          questions[questionIndex]['questionText'] as String,
        ),
        ...(questions[questionIndex]['answers'] as List<Map<String, Object>>)
            .map((answer) {
          return Answer(
              () => answerQuestion(answer['score']), answer['text'] as String);
        }).toList()
      ],
    );
  }
}

型
answer.dart文件：

import 'package:flutter/material.dart';

class Answer extends StatelessWidget {
  final VoidCallback selectHandler;
  final String answerText;

  Answer(this.selectHandler, this.answerText);

  @override
  Widget build(BuildContext context) {
    return Container(
      width: double.infinity,
      child: ElevatedButton(
        style: ButtonStyle(
          backgroundColor: MaterialStateProperty.all(Colors.blue),
          foregroundColor: MaterialStateProperty.all(Colors.white),
        ),
        onPressed: selectHandler,
        child: Text(answerText),
      ),
    );
  }
}

型
和result.dart文件：

import 'package:flutter/material.dart';

class Result extends StatelessWidget {
  final int resultScore;
  final VoidCallback resetHandler;

  Result(this.resultScore, this.resetHandler);

  String get resultPhrase {
    String resultText;
    if (resultScore <= 8) {
      resultText = 'You are awsome and Bigonah';
    } else if (resultScore <= 12) {
      resultText = 'Bad ni';
    } else if (resultScore <= 16) {
      resultText = 'You are Strange';
    } else {
      resultText = 'Go Doctor!';
    }
    return resultText;
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        children: [
          Text(
            resultPhrase,
            style: TextStyle(fontSize: 36, fontWeight: FontWeight.bold),
            textAlign: TextAlign.center,
          ),
          ElevatedButton(
            style: ButtonStyle(
              backgroundColor: MaterialStateProperty.all(Colors.blue),
              foregroundColor: MaterialStateProperty.all(Colors.white),
            ),
            onPressed: resetHandler,
            child: Text('Restart Quiz!'),
          ),
        ],
      ),
    );
  }
}

型