如何在flutter中使用复选框从列表中检索数据

import 'package:flutter/material.dart';

class ListItem {
  String title;
  bool selected;

  ListItem({required this.title, this.selected = false});
}

class CheckboxListPage extends StatefulWidget {
  @override
  _CheckboxListPageState createState() => _CheckboxListPageState();
}

class _CheckboxListPageState extends State<CheckboxListPage> {
  List<ListItem> items = [
    ListItem(title: 'Item 1'),
    ListItem(title: 'Item 2'),
    ListItem(title: 'Item 3'),
    ListItem(title: 'Item 4'),
  ];

  List<ListItem> selectedItems = [];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Checkbox List'),
      ),
      body: ListView.builder(
        itemCount: items.length,
        itemBuilder: (context, index) {
          return ListTile(
            title: Text(items[index].title),
            leading: Checkbox(
              value: items[index].selected,
              onChanged: (value) {
                setState(() {
                  items[index].selected = value!;
                  if (value) {
                    selectedItems.add(items[index]);
                  } else {
                    selectedItems.remove(items[index]);
                  }
                });
              },
            ),
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // 处理选中的数据
          for (var item in selectedItems) {
            print(item.title);
          }
        },
        child: Icon(Icons.check),
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: CheckboxListPage(),
  ));
}