从获取JSON API列表数据(Fetch JSON list data from api)

我想取的从返回JSON格式的，像这样的端点问题的列表：

[
  {
    "id": 1,
    "question": "text",
    "option1": "text",
    "option2": "text",
    "option3": "text",
    "option4": "text",
    "answer": "text"
  },
  {
    "id": 2,
    "question": "text",
    "option1": "text",
    "option2": "text",
    "option3": "text",
    "option4": "text",
    "answer": "text"
  }
]

下面的例子在这里，我有一个测验类：

class Quiz extends Object with _$QuizSerializerMixin {
  List<Question> questions;

  Quiz(this.questions);

  factory Quiz.fromJson(Map<String, dynamic> json) => _$QuizFromJson(json);
}

和问题类：

class Question extends Object with _$QuestionSerializerMixin {

  final String question;
  final String option1;
  final String option2;
  final String option3;
  final String option4;
  final String answer;

  Question(
      {this.question,
      this.option1,
      this.option2,
      this.option3,
      this.option4,
      this.answer});

  factory Question.fromJson(Map<String, dynamic> json) =>
      _$QuestionFromJson(json);
}

与函数定义为：

Future<Quiz> fetchQuiz() async {
  final response = await http.get('json_endpoint.placeholder/questions');

  if (response.statusCode == 200) {
    return Quiz.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to load quiz');
  }
}

我怎么进入竞猜的新实例吗？这可能是显而易见的，但我发现很难。

我曾尝试声明一个变量，如下所示：

class QuizScreen extends StatefulWidget {
  @override
  _QuizScreenState createState() => _QuizScreenState();
}

class _QuizScreenState extends State<QuizScreen> {
Question question
String option1
...

Quiz quiz = quiz(fetchQuiz());

@override
void initState() {
super.initState();
question = quiz.nextQuestion;
option1 = question.option1;
...

Quiz quiz = Quiz(fetchQuiz()); 抛出一个错误。

Answer 1:

该代码看起来应该像

Future foo() async {
  Quiz quiz = await fetchQuiz();
}

fetchQuiz()返回一个Future<Quiz> ，并获得价值了，你使用await ，对于包含（代码函数foo()在我的例子），需要进行async 。

Answer 2:

我认为你正在寻找FutureBuilder 。它可以让你打造UI的时候Future完成。其结果将是snapshot.data如果snapshot.hasData == true 。

@override
  Widget build(BuildContext context) {
    return Scaffold(
        body: FutureBuilder<Quiz>(
      future: fetchQuiz(),
      builder: (context, snapshot) {
        if (snapshot.hasData) {
          return _buildQuiz(context, snapshot.data);
        } else if (snapshot.hasError) {
          return Text('${snapshot.error}');
        }
        return Center(child: CircularProgressIndicator());
      },
    ));
  }

void _buildQuiz(BuildContext context, Quiz quiz) {

}