我想在flutter中使用共享首选项，但是"Object“类型不能分配给"bool”。

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool _isSwitched = false;

  @override
  void initState() {
    super.initState();
    _loadData();
  }

  Future<void> _loadData() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    bool? value = prefs.getBool('myBoolKey');
    if (value != null) {
      setState(() {
        _isSwitched = value;
      });
    }
  }

  Future<void> _saveData(bool value) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    await prefs.setBool('myBoolKey', value);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Shared Preferences Example'),
      ),
      body: Center(
        child: Switch(
          value: _isSwitched,
          onChanged: (value) {
            setState(() {
              _isSwitched = value;
              _saveData(value);
            });
          },
        ),
      ),
    );
  }
}