我无法使用 Flutter 中的 API 将数据从一个页面传输到另一个页面。 它总是打印我已经初始化的数据

Question

我的代码运行良好，但没有打印所选国家/地区的适当时间。 它总是打印德里及其时间只是因为我已经在 loading.dart 文件中对其进行了初始化（ universalTime instance=UniversalTime(location: 'Delhi',time: 'j', flag: 'Flag_of_India.png', url:'Asia/Kolkata',isdaytime: true); ).如果我将城市和网址更改为列表中的任何其他国家，它只会打印该城市的名称和时间。 它应该使用 API 从choose_location.dart 文件中获取数据。 这意味着在运行代码后，应用程序在我的手机中构建，如果我将手机中的应用程序的位置更改为其他城市，例如从德里到柏林，它仍然会打印德里及其时间。因此它不会从选择位置获取数据。 dart 文件，当我在手机中构建应用程序后选择其他位置时。

main.dart

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


void main() => runApp(MaterialApp(
  initialRoute: '/location',
  routes: {
    '/':(context)=>Loading(),
    '/home':(context)=>Home(),
    '/location':(context)=>ChooseLocation(),
  },
));

选择位置.dart

import 'package:path/path.dart';
import 'package:flutter/material.dart';
import'package:universal_time_app/services/universal_time.dart';
//import 'package:universal_time_app/pages/loading.dart';
//import 'package:universal_time_app/pages/home.dart';
import 'dart:developer';




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

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

List<UniversalTime> locations = [
  UniversalTime(url: 'Europe/London', location: 'London', flag: 'UK.png',time:'w',isdaytime:true),
  UniversalTime(url: 'Europe/Athens', location: 'Athens', flag: 'Greece.png',time:'w',isdaytime: true),
  UniversalTime(url: 'Africa/Cairo', location: 'Cairo', flag: 'Egypt.png',time:'w',isdaytime: true),
  UniversalTime(url: 'Africa/Nairobi', location: 'Nairobi', flag: 'Kenya.png',time:'w',isdaytime: true),
  UniversalTime(url: 'America/Chicago', location: 'Chicago', flag: 'usa.png',time:'w',isdaytime: true),
  UniversalTime(url: 'America/New_York', location: 'New York', flag: 'usa.png',time:'w',isdaytime: true),
  UniversalTime(url: 'Asia/Seoul', location: 'Seoul', flag: 'South_Korea.png',time:'w',isdaytime: true),
  UniversalTime(url: 'Asia/Jakarta', location: 'Jakarta', flag: 'Indonesia.png',time:'w',isdaytime: true),
  UniversalTime(url: 'Asia/Kolkata', location: 'Delhi', flag: 'India.png',time:'w',isdaytime: true),
];


void updateTime(index,context) async {
   UniversalTime instance = locations[index];
  log('rdygcvjhbnlk');
  await instance.getTime();
  //navigate to home screen

      Navigator.pop(context,{
        'location': instance.location,
        'flag': instance.flag,
        'time': instance.time,
        'isdaytime': instance.isdaytime
      });

   print( locations[index].location);
   print(index);

}

class _ChooseLocationState extends State<ChooseLocation> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.blueGrey,
      appBar: AppBar(
        backgroundColor: Colors.greenAccent,
        title: Text('Choose a location'),
        centerTitle: true,
        elevation: 0,
      ),
      body: ListView.builder(
        itemCount:locations.length,
        itemBuilder: (context,index) {
          print('gintama');
          print(index);
          print( locations[index].location);
          return Padding(
            padding: const EdgeInsets.symmetric(vertical: 10.0,horizontal:10.0 ),
            child: Card(
              child: ListTile(
                onTap: () {
                  updateTime(index,context);
                },

                title: Text(
                    locations[index].location),
                leading: CircleAvatar(
                  backgroundImage: AssetImage('assets/Flag_of_${locations[index].flag}'),

                ),

              ),
            ),
          );
        }
      ),

    );
  }
}

加载.dart

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

class Loading extends StatefulWidget {
  const Loading({Key? key}) : super(key: key);
  @override
  _LoadingState createState() => _LoadingState();
}
class _LoadingState extends State<Loading> {
void setupWorldTime () async {
  UniversalTime instance=UniversalTime(location: 'Delhi',time: 'j', flag: 'Flag_of_the_Germany.png', url:'Asia/Kolkata',isdaytime: true);
     await instance.getTime();
     Navigator.pushReplacementNamed(context, '/home',arguments: {
       'location':instance.location, 'flag':instance.flag,'time':instance.time, 'isdaytime':instance.isdaytime,
     });

}

@override
void initState(){
    super.initState();
    setupWorldTime();
}
@override
  Widget build(BuildContext context) {
    return const Scaffold(
      backgroundColor: Colors.greenAccent,
      body:Center(
        child: SpinKitPouringHourGlassRefined(
          color: Colors.white,
          size: 100.0,
        ),
      ),
    );
  }
}

家.dart

import 'package:flutter/material.dart';
import 'package:universal_time_app/services/universal_time.dart';
import 'dart:developer';

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

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

class _HomeState extends State<Home> {

  Map data={};

  @override
  Widget build(BuildContext context) {


    data = ModalRoute.of(context)!.settings.arguments as Map;
    //data=data.isEmpty ? data: ModalRoute.of(context)?.settings.arguments as Map;
    print(data);
    String bgImage='Nw1.jpg';

    //set bg image
     if (data['isdaytime'] == true) {
       bgImage = 'Dw.jpg';
      }
    //print(bgImage);

    //bgImage=data['isdaytime']?'Dw.jpg':'Nw1.jpg';
    return
       Scaffold(
         body:Container(
           decoration: BoxDecoration(
             image: DecorationImage(
               image:AssetImage('assets/$bgImage'),
                   fit: BoxFit.cover,
             ),
           ),
           child: SafeArea(
            child:Column(
              children:<Widget>[
                TextButton.icon(
                    onPressed:(
                    ) async {
                     dynamic result = await Navigator.pushNamed(context, '/location');
                     setState(() {
                       data ={
                         'time' : result['time'],
                         'location' : result['location'],
                         'isdatime':result['isdaytime'],
                         'flag': result['flag'],
                       };
                     });
                     },
                    icon:Icon(Icons.edit_location_rounded,size:45.0,color: Colors.orange,),
                  label: Text(
                      'Edit Location',
                    style: TextStyle(
                      fontSize: 25.0,
                      color: Colors.white,
                    ),
                  ),
                ),
                SizedBox(height: 230.0,),
                Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: <Widget>[
                    Text(
                      data['location'],
                      style: TextStyle(
                        color: Colors.yellowAccent,
                        fontSize: 50.0,
                        letterSpacing: 2.0,
                      ),
                    ),
                  ],
                ),
                SizedBox(height: 20.0,),
                Text(
                  data['time'],
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 70.0,
                    letterSpacing: 2.0,
                  ),
                ),
              ],
            ),
           ),
         ),
       );
  }
}

Universal_time.dart

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

class UniversalTime {

  String location;
  String time;
  String flag;
  String url;
  bool isdaytime;

  UniversalTime({
    required this.time,required this.isdaytime,
    required this.location,required this.flag,required this.url});

  Future <void> getTime() async {
try {
//make request
    Response response = await get(Uri.parse('http://worldtimeapi.org/api/timezone/$url'));
    Map data = jsonDecode(response.body);
    String datetime = data['datetime'];
    String offset1 = data['utc_offset'].substring(1,3);
    String offset2 = data['utc_offset'].substring(4,6);

    DateTime now = DateTime.parse(datetime);
    now = now.add(Duration(hours: int.parse(offset1), minutes: int.parse(offset2)));


    
    isdaytime = now.hour > 6 && now.hour < 20;
    //Set the time property
    time=DateFormat.jm().format(now);
  }
  catch (e) {

  print('caught error:$e');
  time='could not get data';
  }

  }

  }

Answer 1

在 home.dart 中使用 .then() 就像

Navigator.pushNamed(context, '/location').then((val){
      print(val['time']);
...
    });