I am totally new to flutter and followed a course and got this far. I am not really sure how to fix the problem.

Expected a value of type 'Map<dynamic, dynamic>', but got one of type 'Null'

Here's the code:

import 'package:flutter/material.dart';

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

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

class _HomepageState extends State<Homepage> {
  Map data = {};
  @override
  Widget build(BuildContext context) {
    data = data.isNotEmpty
        ? data
        : ModalRoute.of(context)!.settings.arguments
            as Map; //Here's where the error occurs...

    String bgi = data['isDaytime'] ? 'day.jpg' : 'night.jpg';

    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: () async {
          dynamic result = await Navigator.pushNamed(context, '/location');
          setState(() {
            if (result != null) {
              data = {
                'time': result['time'],
                'location': result['location'],
                'isDaytime': result['isDaytime'],
                'flag': result['flag']
              };
            }
          });
        },
        materialTapTargetSize: MaterialTapTargetSize.padded,
        elevation: 0,
        backgroundColor: Colors.transparent,
        child: Icon(Icons.gps_fixed_sharp,
            size: 30, color: const Color.fromRGBO(47, 145, 182, 1)),
      ),

[Edited]

This is my arguments:

class _LoadingState extends State<Loading> {
  void setupWorldTime() async {
    WorldTime instance = WorldTime(
      location: 'London',
      flag: 'uk.png',
      url: 'Europe/London',
    );
    await instance.getTime();
    Navigator.pushReplacementNamed(context, '/homepage', arguments: {
      'location': instance.location,
      'flag': instance.flag,
      'time1': 0.toString()   instance.time.substring(0, 1),
      'time2': instance.time.substring(2, 5),
      'isDaytime': instance.isDaytime,
    });
  }

Kindly help me with the solution.

CodePudding user response：

It could be because of the argument is empty or null. Try to assign the variable to nullable map (Map?). So your code will be like this:

    Map? data = {};
  @override
  Widget build(BuildContext context) {
    data = (data?.isNotEmpty ?? false) ? data : ModalRoute.of(context)!.settings.arguments as Map?;