json - 类型 'Future>' 的值不能分配给类型 'List' 的变量

Question

import 'dart:async';
import 'question.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

String opentdb = 'https://opentdb.com/api.php?amount=15&type=boolean';

class QuestionServices {
  Future<List<Question>> getData() async {
    List<Question> questions;
    String link = opentdb;
    var res = await http
        .get(Uri.encodeFull(link), headers: {"Accept": "application/json"});
    print(res.body);
    if (res.statusCode == 200) {
      var data = json.decode(res.body);
      var rest = data['results'] as List;
      print(rest);
      questions =
          rest.map<Question>((json) => Question.fromJson(json)).toList();
    }
    print("List Size: ${questions.length}");
    // _questions = questions;
    return questions;
  }

  List<Question> newQuestions = getData();
}

class Question {
  final String question;
  final bool answer;

  Question({this.question, this.answer});

  factory Question.fromJson(Map<String, dynamic> json) {
    return Question(
      question: json['question'] as String,
      answer: json['correct_answer'] as bool,
    );
  }
}

我正在尝试从 JSON 数据库创建问题列表，但每当我尝试获取返回的列表时，我都会收到错误消息:

"A value of type 'Future<List<Question>>' can't be assigned to a variable of type 'List<Question>'."

我不确定为什么我返回的列表会发出该错误。是否有其他方法可以将 json 添加到列表中？

Answer 1

List<Question> getData() async { // remove Future
    List<Question> questions;
    String link = opentdb;
 ...


//how to access now you will get instance of List<Question>

getData().then((List<Question> newQuestions){

})