I got an error while using Flutter to create a screen that shows the status of a user. Null safety error, but I don't know the solution. The following error message occurred while implementing the process to display the received data of API on the screen.
Error message
The following _CastError was thrown building Consumer<Status>(dirty, dependencies: [_InheritedProviderScope<Status?>]):
Null check operator used on a null value
The relevant error-causing widget was:
Consumer<Status> Consumer:file:///Users/username/StudioProjects/app_name/lib/screens/user_status.dart:55:14
(services/user_status.dart)
import 'package:flutter/material.dart';
import 'package:delivery_kun/models/user_status.dart';
import 'package:dio/dio.dart' as Dio;
import 'package:intl/intl.dart';
import 'dio.dart';
class Status extends ChangeNotifier {
UserStatus? _userStatus;
UserStatus get status => _userStatus!;
String getDate() {
return DateFormat('yyyyMMdd').format(DateTime.now()).toString();
}
void getStatus(int user_id) async {
String date = getDate();
Dio.Response response = await dio()
.get('/status', queryParameters: {'date': date, 'user_id': user_id});
_userStatus = UserStatus.fromJson(response.data);
notifyListeners();
}
}
(models/user.dart)
class UserStatus {
final String onlineTime;
final int daysEarningsTotal;
final int daysEarningsQty;
final String vehicleModel;
final int actualCost;
UserStatus(
{required this.onlineTime,
required this.daysEarningsTotal,
required this.daysEarningsQty,
required this.actualCost,
required this.vehicleModel});
UserStatus.fromJson(Map<String, dynamic> json)
: onlineTime = json['data']['summary']['onlineTime'],
daysEarningsTotal = json['data']['summary']['daysEarningsTotal'],
actualCost = json['data']['summary']['actualCost'],
daysEarningsQty = json['data']['summary']['daysEarningsQty'],
vehicleModel = json['data']['user']['vehicleModel'];
}
screen
class LoggedInUserStatus extends StatelessWidget {
LoggedInUserStatus({required this.user_id});
int user_id;
@override
Widget build(BuildContext context) {
context.read<Status>().getStatus(user_id);
return Container(
child: Consumer<Status>(
builder: (context, status, child) => Column(
children: <Widget>[
Container(
alignment: Alignment.center,
padding: EdgeInsets.only(top: 20),
child: Text(
DateFormat('yyyy年M月d日').format(DateTime.now()),
textAlign: TextAlign.center,
style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold),
)),
Container(
height: 250,
color: Colors.grey,
),
Container(
margin: EdgeInsets.only(right: 15, left: 15),
child: Column(
children: [
Container(
alignment: Alignment.topLeft,
margin: EdgeInsets.only(top: 10),
child: Text(
'ステータス',
style: TextStyle(
fontSize: 25,
),
)),
Table(
border: TableBorder(
bottom:
BorderSide(width: 0.5, color: Color(0xFF000000)),
),
children: [
TableRow(children: [
Text(
'時間',
style: TextStyle(color: Colors.grey),
),
Text('数', style: TextStyle(color: Colors.grey))
]),
TableRow(children: [
TableCell(
child: SizedBox(
height: 50,
child: Text(
status.status.onlineTime,
style: TextStyle(
fontSize: 20,
),
),
),
),
TableCell(
child: SizedBox(
height: 50,
child: Text(
status.status.daysEarningsQty.toString(),
style: TextStyle(
fontSize: 20,
),
),
),
),
]),
]),
Container(
alignment: Alignment.topLeft,
margin: EdgeInsets.only(top: 10),
child: Text(
'明細',
style: TextStyle(
fontSize: 30,
),
)),
Table(children: [
TableRow(children: [
Text(
'売上',
style: TextStyle(
color: Colors.black,
fontSize: 20,
),
),
Text(status.status.daysEarningsTotal.toString(),
textAlign: TextAlign.right,
style: TextStyle(
color: Colors.black,
fontSize: 20,
))
]),
TableRow(children: [
TableCell(
child: SizedBox(
height: 50,
child: Text(
'支出',
style: TextStyle(
fontSize: 20,
),
),
),
),
TableCell(
child: SizedBox(
height: 50,
child: Text(
status.status.actualCost.toString(),
textAlign: TextAlign.right,
style: TextStyle(
fontSize: 20,
),
),
),
),
]),
TableRow(children: [
TableCell(
child: SizedBox(
height: 50,
child: Text(
'利益',
style: TextStyle(
fontSize: 20,
),
),
),
),
TableCell(
child: SizedBox(
height: 50,
child: Text(
(status.status.daysEarningsTotal -
status.status.actualCost)
.toString(),
textAlign: TextAlign.right,
style: TextStyle(
fontSize: 20,
),
),
),
),
]),
]),
ElevatedButton(
onPressed: () {},
child: Text( 'ボタン'),
style: ElevatedButton.styleFrom(
primary: Colors.grey,
minimumSize: Size(double.infinity, 55),
),
),
],
))
],
),
),
);
}
}
