The getter 'data' was called on null. Receiver: null Tried calling: data - firebase

Question

Tried signing up user with Firebase but got the above error instead, and the code is formatted in such a way that it should redirect the user to homepage after a successful signup.
My main.dart
import 'package:bedc_app/home_page.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:bedc_app/auth/login_page.dart';
void main() async{
//solution study
WidgetsFlutterBinding.ensureInitialized();
FirebaseAuth.instance.currentUser()
.then((FirebaseUser user) {
if(user != null){
Firestore.instance.collection('users').document(user.uid).get().then((DocumentSnapshot doc){
runApp(MyApp(true, doc));
});
return;
}
runApp(MyApp(false, null));
});
}
// void main() =>runApp(MyApp());
class MyApp extends StatelessWidget {
bool isLoggedIn;
DocumentSnapshot doc;
MyApp(this.isLoggedIn, this.doc);
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'My Multifunctional bedc project App',
debugShowCheckedModeBanner: false,
home: isLoggedIn ? HomePage(userDoc: doc) : loginPage(),
);
}
}
My Signup_page.dart
import 'package:bedc_app/auth/login_page.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:bedc_app/utils/constants.dart';
import '../home_page.dart';
class SignUpPage extends StatefulWidget {
#override
_SignUpPageState createState() => _SignUpPageState();
}
class _SignUpPageState extends State<SignUpPage> {
String email, password;
bool isLoggedIn = false;
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.white,
body: ListView(
children: [
SizedBox(
height: 50,
),
Align(
alignment: Alignment.topCenter,
child: (
Image.asset(
'assets/bedclogo.jpg'
)),
),
SizedBox(
height: 100,
),
Padding(
padding: EdgeInsets.symmetric(horizontal: 26.0),
child: TextField(
decoration: InputDecoration(
hintText: 'email',
border: OutlineInputBorder(),
labelText: 'Email',
suffixIcon: Icon(Icons.email, color: Colors.green)
),
keyboardType: TextInputType.emailAddress,
onChanged: (String val){
email = val;
},
),
),
SizedBox(
height: 10,
),
Padding(
padding: EdgeInsets.symmetric(horizontal: 26.0),
child: TextField(
decoration: InputDecoration(
hintText: 'Password',
border: OutlineInputBorder(),
labelText: 'Password',
suffixIcon: Icon(Icons.lock, color: Colors.green)
),
obscureText: true,
obscuringCharacter: '!',
keyboardType: TextInputType.emailAddress,
onChanged: (String val){
password = val;
},
),),
SizedBox(
height: 5,
),
Padding(
padding: EdgeInsets.symmetric(horizontal: 26),
child: MaterialButton(
color: Color(0xFF88C540),
child: isLoading ? Container(
height: 24,
width: 24,
child: CircularProgressIndicator(
valueColor: AlwaysStoppedAnimation<Color>(Colors.black),
strokeWidth: 2,
)
):Text(
'SignUp'.toUpperCase(),
style: TextStyle(fontWeight: FontWeight.bold),
),
onPressed: (){
checkUserInput();
},
),
),
SizedBox(
height: 10,
),
Padding(
padding: EdgeInsets.symmetric(horizontal: 20),
child: RichText(
text: TextSpan(
text: 'Already have an Account ?',
style: TextStyle(color: Colors.black),
children: [
TextSpan(
text: 'Login here',
style: TextStyle(color: Colors.blue),
recognizer: TapGestureRecognizer()..onTap = (){
Navigator.of(context).pushReplacement(CupertinoPageRoute(builder: (_) => loginPage()));
},
)
]
)),
)
],
));
}
//SIGNUP FUNCTION USING FIREBASE
bool isLoading = false;
signUpUserWithFirebase(){
FirebaseAuth.instance.createUserWithEmailAndPassword(
email: email,
password: password
).then((AuthResult result){
//Authresult cant be stored to string.....
storeUserDataToFirestore(result.user.uid);
if(result.user.uid != null){
Navigator.of(context).pushReplacement(MaterialPageRoute(builder: (_) => HomePage()));
}
}).catchError((e){
print(e);
isLoading = false;
setState(() { });
});
}
//storeUserDataToFirestore
storeUserDataToFirestore(String userId){
Map<String, dynamic> userData = Map<String, dynamic>();
userData = {
Constants.USERNAME: '#username',
Constants.USER_ID: userId,
Constants.EMAIL : email,
Constants.ACCOUNT_NUM : '00000000',
Constants.IS_ADMIN: false,
Constants.PROFILE_IMAGE: '',
Constants.PROFILE_IMAGE_THUMB: '',
};
CollectionReference usersRef = Firestore.instance.collection(Constants.USERS_COLLECTION);
usersRef.document(userId).setData(userData).then((_){
isLoading = false;
setState(() { });
}).catchError((e){
print(e);
});
}
//FUNCTION TO CHECK USER ENTRY
checkUserInput(){
isLoading = true;
setState(() { });
if(email == null || email.isEmpty){
print('Enter email');
isLoading = false;
setState(() { });
return;
}
if(password == null || email.isEmpty){
print('Enter password');
isLoading = false;
setState(() { });
}
//SIGNUP THE USER
signUpUserWithFirebase();
}
getUserData(String UserId){
Firestore.instance.collection(Constants.USERS_COLLECTION)
.document(UserId)
.get().then((DocumentSnapshot userDoc){
Navigator.of(context).pop();
Navigator.of(context).pushReplacement(CupertinoPageRoute(builder: (_) => HomePage(userDoc: userDoc)));
}).catchError((e){
print(e);
});
}
}
My Home_page.dart
import 'dart:ui';
import 'package:bedc_app/auth/login_page.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'package:bedc_app/auth/signup_page.dart';
import 'model/user.dart';
User currentUser;
class HomePage extends StatefulWidget {
DocumentSnapshot userDoc;
HomePage({this.userDoc,});
#override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
//user cant access this page unless logged in
bool userIsLoggedIn = true;
#override
void initState() {
// TODO: implement initState
super.initState();
currentUser = User.fromSnapshot(widget.userDoc);
}
//HERE IS BUILDING PROFILE IMAGE
Widget buildProfileImage(){
if(currentUser.profileImage == ''){
return CircleAvatar(
backgroundColor: Colors.white70,
radius: 20,
child: Icon(Icons.person, size: 30),
);
}else{
return CircleAvatar(
backgroundImage: NetworkImage(currentUser.profileImage),
);
}
}
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
automaticallyImplyLeading: false,
backgroundColor: Colors.brown,
title: Text('Homepage'),
),
body: ListView(
children: [
SizedBox(height: 20),
Align(
alignment: Alignment.topRight,
child: (
Image.asset(
'assets/bedclogo.jpg',
scale: 2,
)),
),
ListTile(
title: Text(currentUser.username, style: TextStyle(color: Colors.brown, fontWeight: FontWeight.bold),),
leading: buildProfileImage(),
),
SizedBox(height: 30),
//CAPTURE METER READING UI
Padding(
padding: const EdgeInsets.symmetric(horizontal: 20.0),
child: GestureDetector(
onTap: (){
//print(currentUser.isAdmin);
},
child: Row(
children: [
//CAPTURE METR READING
Container(
width: 100,
height: 100,
color: Colors.green,
child: Align(
alignment: Alignment.center,
child: (
Image.asset(
'assets/meterIcon.png',
scale: 3,
)),
),
),
Container(
width: 100,
height: 100,
child: Align(
alignment: Alignment.center,
child: Text('Capture Meter Reading'.toUpperCase()),
),
),
],
),
),
),
SizedBox(height: 30),
//UPDATE PROFILE UI DESIGN
Padding(
padding: const EdgeInsets.symmetric(horizontal: 20.0),
child: GestureDetector(
onTap:(){
//print(currentUser.isAdmin);
},
child: Row(
children: [
Container(
width: 100,
height: 100,
color: Colors.green,
child: Align(
alignment: Alignment.center,
child: (
Image.asset(
'assets/profileAvatar.png',
scale: 3,
)),
),
),
Container(
width: 100,
height: 100,
child: Align(
alignment: Alignment.center,
child: Text('Update Profile'.toUpperCase()),
),
),
],
),
),
),
// TextButton (
// onPressed: (){
// //just logout, implement pop dialog later
// // FirebaseAuth.instance.signOut();
// // Navigator.of(context).pushReplacement(CupertinoPageRoute(builder: (_)=> loginPage()));
// // currentUser = null;
// // setState(() {
// // });
// // still showing error... try to fix asap
// FirebaseAuth.instance.signOut().then((_){
// userIsLoggedIn = false;
// Navigator.of(context).pushReplacement(MaterialPageRoute(builder: (_)=> loginPage()));
// //currentUser = null;
// setState(() {
//
// });
// });
// },
// child: Text('SignOut'))
],
)
);
}
}
User.dart for user Model
import 'package:bedc_app/utils/constants.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
class User{
String username;
String email;
String userId;
String accountNum;
bool isAdmin;
String profileImage;
String profileImageThumb;
User({
this.username,
this.email,
this.userId,
this.accountNum,
this.isAdmin,
this.profileImage,
this.profileImageThumb
});
factory User.fromSnapshot(DocumentSnapshot doc){
return User(
username: doc.data[Constants.USERNAME],
email: doc.data[Constants.EMAIL],
userId: doc.data[Constants.USER_ID],
accountNum: doc.data[Constants.ACCOUNT_NUM],
isAdmin: doc.data[Constants.IS_ADMIN],
profileImage: doc.data[Constants.PROFILE_IMAGE],
profileImageThumb: doc.data[Constants.PROFILE_IMAGE_THUMB]
);
}
}
Having signed the user up, im getting error The getter 'data' was called on null. Receiver: null Tried calling: data.
i dont know which part of the code is causing this exception

Answer 1

This error generally show when you try to get some attribute on null object.
In your case, call one of doc.data[..] in file User.dart generate the error that means doc == null is true.
Verify that widget.userDoc is not null at this line currentUser = User.fromSnapshot(widget.userDoc); on initState method of Home_page.dart file
So error provide in one of HomePage call who require a non null userDoc (todo: make sure your data is not null using assert and add #required before required variable on your class exp: HomePage({#required this.userDoc,}): assert(userDoc != null, "BOooh my userDoc may be not null"); that help very much when you debug your app)
finaly your problem provide in signUpUserWithFirebase() method of your Signup_page.dart file... here Navigator.of(context).pushReplacement(MaterialPageRoute(builder: (_) => HomePage()));
Try to replace by this getUserData(result.user.uid) so your methode should become
signUpUserWithFirebase(){
FirebaseAuth.instance.createUserWithEmailAndPassword(
email: email,
password: password
).then((AuthResult result){
//Authresult cant be stored to string.....
storeUserDataToFirestore(result.user.uid);
if(result.user.uid != null){
getUserData(result.user.uid); // replaced line
}
}).catchError((e){
print(e);
isLoading = false;
setState(() { });
});
}