NoSuchMethod Error: Method called on null - flutter

Question

//in this code i am tring to use connectivity. Android recommended me to add some classes, //getters setter, I added them at the end of the code automatically
import 'package:firebase_auth/firebase_auth.dart';[enter image description here][1]
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'signup.dart';
import 'home.dart';
import 'dart:async';
import 'dart:developer' as developer;
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
class Login extends StatefulWidget {
const Login({Key? key}) : super(key: key);
#override
_LoginState createState() => _LoginState();
}
//loginstate
class _LoginState extends State<Login> {
ConnectivityResult? _connectionStatus = ConnectivityResult.none;
final Connectivity _connectivity = Connectivity();
late StreamSubscription<ConnectivityResult> _connectivitySubscription;
#override
void initState() {
super.initState();
initConnectivity();
_connectivitySubscription =
_connectivity.onConnectivityChanged.listen(_updateConnectionStatus);
}
#override
void dispose() {
_connectivitySubscription.cancel();
super.dispose();
}
// Platform messages are asynchronous, so we initialize in an async method.
Future<void> initConnectivity() async {
late ConnectivityResult result;
// Platform messages may fail, so we use a try/catch PlatformException.
try {
result = await _connectivity.checkConnectivity();
} on PlatformException catch (e) {
developer.log('Couldn\'t check connectivity status', error: e);
return;
}
// If the widget was removed from the tree while the asynchronous platform
// message was in flight, we want to discard the reply rather than calling
// setState to update our non-existent appearance.
if (!mounted) {
return Future.value(null);
}
return _updateConnectionStatus(result);
}
Future<void> _updateConnectionStatus(ConnectivityResult result) async {
setState(() {
_connectionStatus = result;
});
}
//Login function
static Future<User?> loiginUsingEmailPassword(
{required String email,
required String password,
required BuildContext context}) async {
FirebaseAuth auth = FirebaseAuth.instance;
User? user;
try {
UserCredential userCredential = await auth.signInWithEmailAndPassword(
email: email, password: password);
user = userCredential.user;
} on FirebaseAuthException catch (e) {
if (e.code == "user-not-found") {
print("No user found for that email");
}
}
return user;
}
#override
Widget build(BuildContext context) {
//create textfield controller
TextEditingController _emailController = TextEditingController();
TextEditingController _passwordController = TextEditingController();
return Scaffold(
resizeToAvoidBottomInset: false,
body: SingleChildScrollView(
child: Column(
children: <Widget>[
Container(
padding: EdgeInsets.fromLTRB(15.0, 110.0, 0.0, 0.0),
child: Text(
'Bon Appétit',
style: TextStyle(
fontFamily: 'Pacifico',
fontSize: 50.0,
),
),
),
//new container
Container(
padding: EdgeInsets.only(top: 35.0, left: 20.0, right: 20.0),
child: Column(
children: [
TextField(
controller: _emailController,
decoration: InputDecoration(
focusedBorder: UnderlineInputBorder(
borderSide: BorderSide(color: Color(0xFFcaa052)),
),
labelText: 'EMAIL',
labelStyle: TextStyle(
fontFamily: 'Alegreya Sans',
fontWeight: FontWeight.bold,
color: Color(0xFFcaa052),
),
),
),
SizedBox(
height: 20.0,
),
TextField(
controller: _passwordController,
decoration: InputDecoration(
focusedBorder: UnderlineInputBorder(
borderSide: BorderSide(color: Color(0xFFcaa052)),
),
labelText: 'PASSWORD',
labelStyle: TextStyle(
fontFamily: 'Alegreya Sans',
fontWeight: FontWeight.bold,
color: Color(0xFFcaa052),
),
),
obscureText: true,
),
SizedBox(
height: 5.0,
),
Container(
alignment: Alignment(1.0, 0.0),
padding: EdgeInsets.only(top: 15.0, left: 20.0),
child: InkWell(
child: Text(
'Forgot Password',
style: TextStyle(
color: Color(0xFF5E0B0B),
fontWeight: FontWeight.bold,
fontFamily: 'Alegreya Sans',
decoration: TextDecoration.underline,
),
),
),
),
SizedBox(
height: 40.0,
),
],
),
),
SizedBox(
height: 15.0,
),
Container(
height: 40.0,
width: 400.0,
child: Material(
borderRadius: BorderRadius.circular(20.0),
shadowColor: Color(0xFFffffb1),
color: Color(0xFFffd180),
elevation: 7.0,
child: InkWell(
onTap: () async {
User? user = await loiginUsingEmailPassword(
email: _emailController.text,
password: _passwordController.text,
context: context);
print(user);
if (user != null) {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => Home()),
);
}
},
child: Center(
child: Text(
'LOGIN',
style: TextStyle(
color: Colors.black,
fontWeight: FontWeight.bold,
fontFamily: 'Alegreya Sans',
),
),
),
),
),
),
Container(
child: Text('Connection Status: ${_connectionStatus.toString()}'),
),
SizedBox(
height: 15.0,
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'New member?',
style: TextStyle(fontFamily: 'Alegreya Sans'),
),
SizedBox(
width: 5.0,
),
InkWell(
onTap: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => Signup()),
);
},
child: Text(
'Sign up',
style: TextStyle(
color: Color(0xFF5E0B0B),
fontWeight: FontWeight.bold,
fontFamily: 'Alegreya Sans',
decoration: TextDecoration.underline,
),
),
),
],
),
],
),
),
);
}
}
//i think because of below code i got error
class ConnectivityResult {
static ConnectivityResult? none;
}
class Connectivity {
get onConnectivityChanged => null;
checkConnectivity() {}
}