Flutter-必须初始化不可为空的实例字段'questionAnswer'，'questionText‘

Question

我正在通过在线课程学习flutter。我正在上创建类的课。因此，我们必须创建一个具有字符串和布尔属性的类。下面是这个类：

class Question {
  String questionText;
  bool questionAnswer;

  Question({required String q, required bool a}) {
    questionText = q;
    questionAnswer = a;
  }
}

错误显示如下：

Non-nullable instance field 'questionText' must be initialized.

Non-nullable instance field 'questionAnswer' must be initialized.

谁来帮帮忙

Answer 1

根据新的null-safety规则，如果不指定变量的值或不执行null检查，就不能初始化任何数据类型的变量。试试这个：

class Question {
  String? questionText;
  bool? questionAnswer;

  Question({@required String q,@required bool a}) {
    questionText = q;
    questionAnswer = a;
  }
}