小部件库捕获异常抛出以下_TypeError：）：类型“Null”不是类型“bool”的子类型

Question

我收到错误。我想在选择时间后更新时间。由于我是颤振的新手，我无法理解颤振。我要离开我工作过的页面。

Main.dart

import 'package:flutter/material.dart';
import 'pages/choose_location.dart';
import 'pages/home.dart';
import 'pages/loading.dart';

void main() => runApp(MaterialApp(
  initialRoute: '/loading', // Change the initialRoute to a valid route
  routes: {
    '/loading': (context) => Loading(),
    '/home': (context) => const Home(),
    '/location': (context) => const ChooseLocation(),
  },
  // Add a home argument for the default route (optional)
  home: Loading(), // You can choose a different widget if needed
));

pages/world_time.dart

import 'package:http/http.dart';
import 'dart:convert';
import 'package:intl/intl.dart';

class WorldTime {
  String location;
  String flag;
  String url;
  String time;
  bool isDaytime;

  WorldTime({
    required this.location,
    required this.flag,
    required this.url,
    required this.time,
    required this.isDaytime,
  });

  Future<void> getTime() async {
    try {
      var uri = Uri.http('worldtimeapi.org', '/api/timezone/$url');
      var response = await get(uri);
      Map data = jsonDecode(response.body);

      // Getting properties from data
      String dateTime = data["datetime"];
      String offset = data["utc_offset"].substring(1, 3);

      // Create datetime object
      DateTime now = DateTime.parse(dateTime);
      now = now.add(Duration(hours: int.parse(offset)));
          isDaytime = now.hour > 6 && now.hour < 20 ? true : false;
          time = DateFormat.jm().format(now);
    } catch (e) {
      print('Caught error: $e');
      time = 'Could not get time data';
    }
  }
}

WorldTime instance = WorldTime(
  location: 'berlin',
  flag: 'germany',
  time: '',
  url: 'Europe/Berlin',
  isDaytime: true, // Set isDaytime here
);

pages/home.dart

import 'package:flutter/material.dart';

class Home extends StatefulWidget {
  const Home({Key? key}) : super(key: key);
  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> {
  Map data = {};

  @override
  Widget build(BuildContext context) {
    data = data.isNotEmpty ? data : ModalRoute.of(context)?.settings.arguments as Map; // Corrected type casting
    print(data);
    //set background
    Color? bgColor = data['isDaytime'] ? Colors.blue : Colors.indigo[700];
      return Scaffold(
      backgroundColor: bgColor,
      body: SafeArea(
        child: Container(
          decoration: const BoxDecoration(
            image: DecorationImage(
                image: AssetImage('assets/day.png'),
                fit: BoxFit.fill,
            ),
          ),
          child: Padding(
            padding: const EdgeInsets.fromLTRB(0.0,120.0,0.0,0.0),
            child: Column(
              children: [
                TextButton.icon(
                  onPressed: () async {
                    dynamic result = await Navigator.of(context).pushNamed('/location'); // Corrected route name
                    setState(() {
                      data = {
                        'time': result['time'],
                        'location': result['location'],
                        'isDayTime': result['isDayTime'], 
                        'flag': result['flag'], 
                      };
                    });
                  },
                  label: const Text('Choose Location',
                  style: TextStyle(color: Colors.white),),
                  icon: const Icon(
                      Icons.edit_location,
                      color: Colors.white,
                  ),
                ),
                  const SizedBox(height: 20.0),
                Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: [
                    Text(
                        data['location'],
                        style: const TextStyle(
                            fontSize:28.0,
                            letterSpacing:2.0,
                          color: Colors.white,
                    ),
                    )],
                ),
                const SizedBox(height: 20.0),
                Text(
                  data['time'],
                  style: const TextStyle(
                      fontSize: 66.0,
                    color: Colors.white,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
    );
  }
}

pages/loading.dart

import 'package:flutter/material.dart';
import 'package:world_time/services/world_time.dart';
import 'package:flutter_spinkit/flutter_spinkit.dart';

class Loading extends StatefulWidget {
  @override
  State<Loading> createState() => _LoadingState();
}

class _LoadingState extends State<Loading> {
  String time = 'loading';
  bool isDaytime = true; // Initialize isDaytime as true or false

  Future<void> setupWorldTime() async {
    WorldTime instance = WorldTime(
      location: 'Berlin',
      flag: 'germany.png',
      time: time,
      url: 'Europe/Berlin',
      isDaytime: isDaytime, // Set isDaytime here
    );
    await instance.getTime();
    Navigator.pushReplacementNamed(context, '/home', arguments: {
      'location': instance.location,
      'flag': instance.flag,
      'time': instance.time,
      'isDaytime': instance.isDaytime,
    });
    print(instance.time);
    setState(() {
      time = instance.time;
    });
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.blue[900],
      body: const Center(
        child: SpinKitFadingCube(
          color: Colors.white,
          size: 50.0,
        ),
      ),
    );
  }
}

页面/选择位置

import 'package:flutter/material.dart';
import 'package:world_time/services/world_time.dart';

class ChooseLocation extends StatefulWidget {
  const ChooseLocation({Key? key}) : super(key: key);

  @override
  State<ChooseLocation> createState() => _ChooseLocationState();
}

class _ChooseLocationState extends State<ChooseLocation> {
  List<WorldTime> locations = [
    WorldTime(location: 'London', flag: 'uk.png', url: 'Europe/London', time: '', isDaytime: true),
    WorldTime(location: 'Athens', flag: 'greece.png', url: 'Europe/Berlin', time: '', isDaytime: true),
    WorldTime(location: 'Cairo', flag: 'egypt.png', url: 'Africa/Cairo', time: '', isDaytime: true),
    WorldTime(location: 'Nairobi', flag: 'kenya.png', url: 'Africa/Nairobi', time: '', isDaytime: true),
    WorldTime(location: 'Chicago', flag: 'usa.png', url: 'America/Chicago', time: '', isDaytime: true),
    WorldTime(location: 'New York', flag: 'usa.png', url: 'America/New_York', time: '', isDaytime: true),
    WorldTime(location: 'Seoul', flag: 'south_korea.png', url: 'Asia/Seoul', time: '', isDaytime: true),
    WorldTime(location: 'Jakarta', flag: 'indonesia.png', url: 'Asia/Jakarta', time: '', isDaytime: true),
  ];

  void updateTime(index) async {
    WorldTime instance = locations[index];
    await instance.getTime();
    print(instance.location);
    // Navigate to the home screen
    // ignore: use_build_context_synchronously
    Navigator.pop(context, {
      'location': instance.location,
      'flag': instance.flag,
      'time': instance.time,
      'isDaytime': instance.isDaytime,
    });
  }

  @override
  Widget build(BuildContext context) {
    print('build function run');
    return Scaffold(
      backgroundColor: Colors.green,
      appBar: AppBar(
        backgroundColor: Colors.blue[900],
        title: const Text('Choose a Location'),
        centerTitle: true, // Center the title
        elevation: 0,
      ),
      body: ListView.builder(
        itemCount: locations.length,
        itemBuilder: (context, index) {
          return Padding(
            padding: const EdgeInsets.symmetric(vertical: 1.0, horizontal: 4.0),
            child: Card(
              child: ListTile(
                onTap: () {
                  updateTime(index);
                },
                title: Text(locations[index].location),
                leading: CircleAvatar(
                  backgroundImage: AssetImage('assets/${locations[index].flag}'),
                ),
              ),
            ),
          );
        },
      ),
    );
  }
}

这是我的主页 当我点击时将选择位置页面 当我选择城市时，它应该在主页上更新它，但会给我一些像这样的错误

Answer 1

在

home.dart

你所做的

setState

你有

'isDayTime': result['isDayTime'], 

这需要

'isDaytime': result['isDaytime'], 

注意你拥有的大写字母

T