Flutter Firebase RealTime Databasee not ordering properly with OrderByChild() [duplicate] - firebase

Question

This question already has an answer here:
Flutter: Firebase Real-Time database orderByChild has no impact on query result
(1 answer)
Closed 2 years ago.
I'm creating a simple application with Firebase Realtime database where a user inputs a text and it gets added to a list of chats.
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.indigo,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
var _firebaseRef = FirebaseDatabase().reference().child('chats');
TextEditingController _txtCtrl = TextEditingController();
#override
Widget build(BuildContext context) {
var comments = _firebaseRef.orderByChild('time').limitToLast(10);
return Scaffold(
body: Container(
child: SafeArea(
child: Column(
children: <Widget>[
Container(
child: Row(children: <Widget>[
Expanded(child: TextField(controller: _txtCtrl)),
SizedBox(
width: 80,
child: OutlineButton(
child: Text("Add"),
onPressed: () {
sendMessage();
}))
])),
StreamBuilder(
stream: comments.onValue,
builder: (context, snap) {
if (snap.hasData &&
!snap.hasError &&
snap.data.snapshot.value != null) {
Map data = snap.data.snapshot.value;
List item = [];
data.forEach(
(index, data) => item.add({"key": index, ...data}));
return Expanded(
child: ListView.builder(
itemCount: item.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(item[index]['message']),
);
},
),
);
} else
return Center(child: Text("No data"));
},
),
],
),
),
),
);
}
sendMessage() {
_firebaseRef.push().set({
"message": _txtCtrl.text,
'time': DateTime.now().millisecondsSinceEpoch
});
}
}
It stores and retrieves data perfectly. But when I try adding data, the new items are placed at random points in the list.
For example, in the image below, the last item I placed into the list was 'Nine'. But it was put in the center of the list:
I've tried sorting the list by timestamps, but it did nothing.
What could be causing this issue? And how can I fix it?

Answer 1

When you call snap.data.snapshot.value; the data in the snapshot (which is ordered) is converted to a Map<String, Object> which isn't ordered. To maintain the order, you'll want to listen to onChild... instead.
Note that FlutterFire has a convenient firebase_list library that handles most of the heavy lifting of onChild... for you.
Also see:
Flutter Firebase Database wrong timestamp order
Flutter sort Firebase snapshot by timestamp
Flutter: Firebase Real-Time database orderByChild has no impact on query result

Answer 2

This might work:
use a Query
Query comments = _firebaseRef.orderByChild('time').limitToLast(10);