A build function returned null. Flutter Firebase - firebase

Question

I tried many things but couldn't get any workable solution, please help.
Even wit the FutureBuilder it doesn't seem to work and without it, I get the result when I hot reload. I don't know how to change the code to make it work. Probably there is something small missing, but I couldn't figure yet what it is or how to solve it.
"""import 'package:flutter/material.dart';
import 'package:list/screens/add_new_item_screen.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
final _firestore = Firestore.instance;
FirebaseUser loggedinUser;
Future<void> _fetchdata;
FirebaseAuth _auth = FirebaseAuth.instance;
class MainPage extends StatefulWidget {
#override
_MainPageState createState() => _MainPageState();
}
class _MainPageState extends State<MainPage> {
void initState() {
super.initState();
_fetchdata = getCurrentUser();
}
Future<void> getCurrentUser() async {
try {
final user = await _auth.currentUser();
if (user != null) {
loggedinUser = user;
// print(loggedinUser.email);
}
} catch (e) {
print(e);
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: () {
Navigator.push(
context, MaterialPageRoute(
builder: (context) => Addnewitem()));
},
child: Icon(Icons.add),
),
appBar: AppBar(
leading: Container(),
title: Text("Shopping List"),
actions: <Widget>[
IconButton(
icon: Icon(Icons.close),
onPressed: () {
// messagesStream();
_auth.signOut();
Navigator.pop(context);
})
],
),
body: SafeArea(child:
MessagesStream(),
),
);
}
}
class MessagesStream extends StatelessWidget {
#override
Widget build(BuildContext context) {
FutureBuilder(
future: _fetchdata,
builder: (context, myFuture){
if (myFuture.connectionState == ConnectionState.done && !myFuture.hasError && myFuture.hasData) {
if (myFuture.data != null) {
return StreamBuilder<QuerySnapshot>(
stream: _firestore
.collection('users')
.document(loggedinUser.uid)
.collection('items')
.snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData || snapshot.hasError || snapshot.data == null || snapshot.connectionState == ConnectionState.waiting || loggedinUser.email == null) {
return (Center(
child: CircularProgressIndicator(
backgroundColor: Colors.lightBlueAccent)));
}
final items = snapshot.data.documents.reversed;
List<MessageBubble> messageBubbles = [];
for (var message in items) {
final item = message.data['item'];
final quant = message.data['quant'];
final id = message.data['id'];
final boli = message.data['bool'];
// final currentUser = loggedinUser.email;
final messageBubble = MessageBubble(
text: item,
quant: quant,
documentReference: message.reference,
);
messageBubbles.add(messageBubble);
}
try {
return Expanded(
child: ListView(
// reverse: true,
padding: EdgeInsets.symmetric(horizontal: 10, vertical: 10),
children: messageBubbles,
),
);
} catch (e) {
return Container();
}
});
}else {
return Container();
}
} else {
return CircularProgressIndicator();
}
});
}
}
class MessageBubble extends StatelessWidget {
MessageBubble({this.text, this.quant, this.documentReference});
final String text;
final String quant;
final DocumentReference documentReference;
#override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: Expanded(
flex: 1,
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Container(
color: Colors.tealAccent,
child: FlatButton(
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(
text,
style: TextStyle(color: Colors.black, fontSize: 20),
),
Text(quant,
style: TextStyle(color: Colors.black, fontSize: 20))
],
),
onPressed: () {
documentReference.delete();
}),
)
],
),
),
);
}
}"""
Flutter doctor:
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
[✓] Xcode - develop for iOS and macOS (Xcode 11.4)
[✓] Chrome - develop for the web
[✓] Android Studio (version 3.5)
[✓] VS Code (version 1.44.0)
[✓] Connected device (3 available)
• No issues found!

Answer 1

You need to add return keyword when using the build function since it returns a Widget:
class MessagesStream extends StatelessWidget {
#override
Widget build(BuildContext context) {
return FutureBuilder(
future: _fetchdata,
builder: (context, myFuture){
if (myFuture.connectionState == ConnectionState.done && !myFuture.hasError && myFuture.hasData) {
if (myFuture.data != null) {
return StreamBuilder<QuerySnapshot>(

Answer 2

For people having the same issue - here is my full code! Hope it helps
import 'package:flutter/material.dart';
import 'package:list/screens/add_new_item_screen.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
final _firestore = Firestore.instance;
FirebaseUser loggedinUser;
Future<void> _fetchdata;
FirebaseAuth _auth = FirebaseAuth.instance;
class MainPage extends StatefulWidget {
#override
_MainPageState createState() => _MainPageState();
}
class _MainPageState extends State<MainPage> {
void initState() {
super.initState();
_fetchdata = getCurrentUser();
}
Future<void> getCurrentUser() async {
try {
final user = await _auth.currentUser();
if (user != null) {
loggedinUser = user;
// print(loggedinUser.email);
}
} catch (e) {
print(e);
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: () {
Navigator.push(
context, MaterialPageRoute(builder: (context) => Addnewitem()));
},
child: Icon(Icons.add),
),
appBar: AppBar(
leading: Container(),
title: Text("Shopping List"),
actions: <Widget>[
IconButton(
icon: Icon(Icons.close),
onPressed: () {
// messagesStream();
_auth.signOut();
Navigator.pop(context);
})
],
),
body: SafeArea(
child: MessagesStream(),
),
);
}
}
class MessagesStream extends StatelessWidget {
#override
Widget build(BuildContext context) {
return FutureBuilder(
future: _fetchdata,
builder: (context, myFuture) {
if (myFuture.connectionState == ConnectionState.done &&
!myFuture.hasError) {
return StreamBuilder<QuerySnapshot>(
stream: _firestore
.collection('users')
.document(loggedinUser.uid)
.collection('items')
.snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData ||
snapshot.hasError ||
snapshot.data == null ||
snapshot.connectionState == ConnectionState.waiting ||
loggedinUser.email == null) {
return (Center(
child: CircularProgressIndicator(
backgroundColor: Colors.lightBlueAccent)));
}
final items = snapshot.data.documents.reversed;
List<MessageBubble> messageBubbles = [];
for (var message in items) {
final item = message.data['item'];
final quant = message.data['quant'];
final id = message.data['id'];
final boli = message.data['bool'];
// final currentUser = loggedinUser.email;
final messageBubble = MessageBubble(
text: item,
quant: quant,
documentReference: message.reference,
);
messageBubbles.add(messageBubble);
}
try {
return Expanded(
child: ListView(
// reverse: true,
padding:
EdgeInsets.symmetric(horizontal: 10, vertical: 10),
children: messageBubbles,
),
);
} catch (e) {
return Container();
}
});
} else {
return CircularProgressIndicator();
}
});
}
}
class MessageBubble extends StatelessWidget {
MessageBubble({this.text, this.quant, this.documentReference});
final String text;
final String quant;
final DocumentReference documentReference;
#override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: Expanded(
flex: 1,
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Container(
color: Colors.tealAccent,
child: FlatButton(
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(
text,
style: TextStyle(color: Colors.black, fontSize: 20),
),
Text(quant,
style: TextStyle(color: Colors.black, fontSize: 20))
],
),
onPressed: () {
documentReference.delete();
}),
)
],
),
),
);
}
}