_TypeError (类型'_Type‘不是’Widget？‘的子类型)

Question

大约6个月前，代码运行良好，然后出现了这种异常。我不知道该怎么做，因为我试图通过使它变为空来修复它，但是它没有起作用，所以我该怎么办呢？代码是一个底部导航栏，这是一个异常图片：

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守则：

    import 'package:blackboard/view/Teacher/AddSheetTeacher.dart';
import 'package:blackboard/view/Teacher/CoursesTeacher.dart';
import 'package:blackboard/view/Teacher/HSTeacher.dart';
import 'package:blackboard/view/Teacher/CoursesTeacher1.dart';
import 'package:flutter/material.dart';
import 'package:blackboard/view/Teacher/HomeScreenTeacher.dart';
import 'package:blackboard/view/Teacher/YourCoursesTeacher.dart';
import 'package:blackboard/view/Teacher/ProfileTeacher.dart';

class dashboard extends StatefulWidget {
  @override
  State<dashboard> createState() => _dashboardState();
}

class _dashboardState extends State<dashboard> {
  int _currentIndex = 0;
  List screens = [CoursesT, HomeScreenTeacher(), HomeScreen()];

  void _updateIndex(int value) {
    setState(() {
      _currentIndex = value;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: screens[_currentIndex],
      bottomNavigationBar: BottomNavigationBar(
        backgroundColor: Colors.transparent,
        elevation: 0,
        type: BottomNavigationBarType.fixed,
        currentIndex: _currentIndex,
        onTap: (_updateIndex),
        selectedItemColor: Colors.purple.shade700,
        selectedFontSize: 13,
        unselectedFontSize: 13,
        iconSize: 30,
        items: [
          BottomNavigationBarItem(
            label: "HomeScreen",
            icon: Icon(
              Icons.home,
              size: 30,
            ),
          ),
          BottomNavigationBarItem(
            label: "Course",
            icon: Icon(
              Icons.book,
              size: 30,
            ),
          ),
          BottomNavigationBarItem(
            label: "Profile",
            icon: Icon(
              Icons.account_box,
              size: 30,
            ),
          ),
        ],
      ),
    );
  }
}

Answer 1

问题就在CoursesT上，它需要在screens中成为CoursesT()。

List<Widget> screens = [CoursesT(), HomeScreenTeacher(), HomeScreen()];