任务屏幕.dart

import 'package:flutter/material.dart';
import 'package:todoey_app/widgets/tasks_list.dart';
import 'package:todoey_app/screens/add_task_screen.dart';
import 'package:todoey_app/models/task.dart';

class TasksScreen extends StatefulWidget {
  @override
  State<TasksScreen> createState() => _TasksScreenState();
}

class _TasksScreenState extends State<TasksScreen> {
  List<Task> tasks = [
    Task(name: 'Buy milk'),
    Task(name: 'Buy eggs'),
    Task(name: 'Buy bread'),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.lightBlueAccent,
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () {
          showModalBottomSheet(
            context: context,
            builder: (context) => AddTaskScreen(
              (newTaskTitle) {
                // print(newTaskTitle);
                setState(() {
                  tasks.add(Task(name: newTaskTitle));
                });
                Navigator.pop(context);
              },
            ),
          );
        },
      ),
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Container(
            padding: EdgeInsets.only(
                top: 60.0, left: 30.0, right: 30.0, bottom: 30.0),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                CircleAvatar(
                  child: Icon(
                    Icons.list,
                    size: 30.0,
                    color: Colors.lightBlueAccent,
                  ),
                  backgroundColor: Colors.white,
                  radius: 30.0,
                ),
                SizedBox(
                  height: 10.0,
                ),
                Text(
                  'Todoey',
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 50.0,
                    fontWeight: FontWeight.w700,
                  ),
                ),
                Text(
                  '${tasks.length} Tasks',
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 18.0,
                  ),
                ),
              ],
            ),
          ),
          Expanded(
            child: Container(
              padding: EdgeInsets.symmetric(horizontal: 20.0),
              decoration: BoxDecoration(
                  color: Colors.white,
                  borderRadius: BorderRadius.only(
                    topRight: Radius.circular(20.0),
                    topLeft: Radius.circular(20.0),
                  )),
              child: TasksList(tasks),
            ),
          ),
        ],
      ),
    );
  }
}

add_task_screen.dart

import 'package:flutter/material.dart';

class AddTaskScreen extends StatelessWidget {
  final Function addTaskCallback;

  AddTaskScreen(this.addTaskCallback);

  @override
  Widget build(BuildContext context) {
    // String? newTaskTitle;
    // String newTaskTitle = '';
    String newTaskTitle = "It's Working";
    // String newTaskTitle;

    return Container(
      color: Color(0xff757575),
      child: Container(
        padding: EdgeInsets.all(20.0),
        decoration: BoxDecoration(
            color: Colors.white,
            borderRadius: BorderRadius.only(
              topLeft: Radius.circular(20.0),
              topRight: Radius.circular(20.0),
            )),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Text(
              'Add Task',
              textAlign: TextAlign.center,
              style: TextStyle(
                color: Colors.lightBlueAccent,
                fontSize: 30.0,
              ),
            ),
            TextField(
              autofocus: true,
              textAlign: TextAlign.center,
              onChanged: (newText) {
                // print(newText);
                newTaskTitle = newText;
              },
            ),
            TextButton(
              onPressed: () {
                print(newTaskTitle);
                addTaskCallback(newTaskTitle);
              },
              child: Text(
                'Add',
                style: TextStyle(color: Colors.white),
              ),
              style: TextButton.styleFrom(
                backgroundColor: Colors.lightBlueAccent,
              ),
            )
          ],
        ),
      ),
    );
  }
}

我已经初始化了newTaskTitle，但是当我在TextField中键入新文本并尝试将其添加到任务列表中时，它只接受我在开始时初始化的值newTaskTitle =“It 's Working”，而不是接受来自textField的新值;。
我该怎么解决呢？