I tried this code but the tenary operator is not working as it should as I am getting error and if put String bgImage = (data['isDayTime']==null)? 'day.png' : 'night.png'; then I am only getting day.png I am getting this error

The following TypeErrorImpl was thrown building Home(dirty, dependencies: [_ModalScopeStatus], state: _HomeState#1a387): type 'Null' is not a 'bool' in boolean expression

Here is the code

import 'package:flutter/material.dart';

class Home extends StatefulWidget {
  @override
  _HomeState 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;
    print(data);

    String bgImage = data['isDayTime']? 'day.png' : 'night.png';

    return Scaffold(
      body: SafeArea(
          child: Container(
            decoration: BoxDecoration(
              image: DecorationImage(
                image: AssetImage('assets/$bgImage'),
                fit: BoxFit.cover,
              )
            ),
            child: Padding(
              padding: const EdgeInsets.fromLTRB(0,120.0,0,0),
              child: Column(
                  children: <Widget>[
                    FlatButton.icon(
                      onPressed: () async {
                       dynamic result = await Navigator.pushNamed(context, '/location');
                       setState(() {
                         data ={
                           'time': result['time'],
                           'location': result['location'],
                           'isDaytime': result['isDaytime'],
                           'flag': result['flag'],
                         };
                       });
              },
                      icon: Icon(
                          Icons.edit_location,
                          color: Colors.grey[300],
                      ),
                      label: Text(
                          'Edit Location',
                          style: TextStyle(
                            color: Colors.grey[300],

                      ),
                      ),
                    ),

                  SizedBox(height: 20.0),
                    Row(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        Text(
                         data['location'],
                         style: TextStyle(
                           fontSize: 28.0,
                           letterSpacing: 2.0
                         )
                        )
                      ],
                    ),
                    SizedBox(height: 20.0),
                    Text(
                      data['time'],
                      style: TextStyle(
                        fontSize: 66.0,
                      ),
                    ),
                  ],
              ),
            ),
          ),
      ),
    );
  }
}

CodePudding user response：

Change your condition from data['isDayTime']? to data['isDayTime']!=null && data['isDayTime']==true?.

CodePudding user response：

The main issue is here you are passing bool? isDaytime and this is nullable means it can be null. But using String bgImage = data['isDayTime']? 'day.png' : 'night.png'; means here data['isDayTime'] either will be true or false. That's why you need to make sure you are not getting null value. Also, another null value can occur from modal route arguments.

1stly check if data['isDayTime'] is null or not, then check it. You can follow @Monik's answer.