您是否尝试过添加as String？
questions[_questionIndex]['questionText'] as String

您的类Question需要构造函数中的字符串参数。
questions[_questionIndex]['questionText'] as String可以解决此问题。
更干净的解决方案是将questions变量定义为List<Map<String, dynamic>> questions，或者甚至为question创建一个单独的模型以避免双重索引。

class QuestionModel {
  String questionText;
  List<String> answers;

  QuestionModel({required this.questionText, required this.answers});
}

并将问题定义为

List<QuestionModel> questions = [
  QuestionModel(
    questionText: "What is your favourite color?",
    answers: ["Red", "Green", "Blue", "Yellow"],
  ),
  ...
];

从列表中访问问题：

questions[_questionIndex].questionText

questions[_questionIndex]['questionText'].toString();