您需要将想要为其创建状态的小部件类型从有状态小部件传递到状态类：

import 'package:flutter/material.dart';
import 'task_tile.dart';
import 'package:todoey_flutter/models/task.dart';
import 'package:todoey_flutter/screens/tasks_screen.dart';

class TaskList extends StatefulWidget {
  TaskList({required this.tasks});

 final List tasks;

 @override
 _TaskListState createState() => _TaskListState();
 }

class _TaskListState extends State<TaskList> { // ADD <TaskList> 
 @override
Widget build(BuildContext context) {
return ListView.builder(
  itemBuilder: (context, index) {
    return TaskTile(
      taskTitle: widget.tasks[index].name,
      isChecked: widget.tasks[index].isDone,
      checkboxCallback: (checkboxState) {
        setState(() {
          widget.tasks[index].toggleDone();
        });
      },
    );
  },
  itemCount: widget.tasks.length,
);
}