错误在 StudentAdd(List.. and _StudentAddState(Lİst.. in first and second class) 给出

错误两次对我说“必须初始化不可为空的实例字段‘学生’。”和 必须初始化不可为 null 的实例字段“students”。

我所有的代码:

class StudentAdd extends StatefulWidget {

  List<Student> students;
  StudentAdd(List<Student> students){

    this.students = students;
  }

  @override
  State<StatefulWidget> createState() {
    return _StudentAddState(students);
  
}
}

class _StudentAddState extends State with StudentValidationMixin {

  List<Student> students;

  var student = Student.withInfo(0, '', '', 0);

  var formKey = GlobalKey<FormState>();


  _StudentAddState(List<Student> students){

    this.students = students;
  }
  @override

  Widget build(BuildContext context) {

    // TODO: implement build

    return Scaffold(

      appBar: AppBar(

        title: Text('Yeni Öğrenci Ekle'),
      ),
      body: Container(

        margin: EdgeInsets.all(20.0),
        //margin: EdgeInsets.only(top: 20.0, right: 20.0, left: 20.0),
        child: Form(
          key: formKey,
          child: Column(
            children: <Widget>[
              buildFirstNameField(),
              buildLastNameField(),
              buildGradeField(),
              buildSubmitButton(),
            ],
          ),
        ),
      ),
    );
  }