Flutter - fill list with firebase collection - dart

Question

I have a list of messages that I want to fill on init with a firebase collection.
import 'package:flutter/material.dart';
import 'package:my_first_flutter_app/chatmessage.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:logging/logging.dart';
final Logger log = new Logger('ChatScreen');
class ChatScreen extends StatefulWidget {
#override
State createState() => new ChatScreenState();
}
class ChatScreenState extends State<ChatScreen> {
final TextEditingController _chatController = new TextEditingController();
final List<ChatMessage> _messages = <ChatMessage>[];
#override
Widget build(BuildContext context) {
return new Column(
children: <Widget>[
new Flexible(
child: ListView.builder(
padding: new EdgeInsets.all(8.0),
reverse: true,
itemBuilder: (_, int index) => _messages[index],
itemCount: _messages.length,
),
),
new Divider(
height: 1.0,
),
new Container(decoration: new BoxDecoration(
color: Theme.of(context).cardColor,
),
child: _chatEnvironment(),)
],
);
}
}
I tried to do this:
#override
Widget build(BuildContext context) {
Firestore.instance
.collection('chats')
.document('ROOM_1')
.collection("messages")
.getDocuments()
.then((snap) {
return new Column(
....
but I need to return a Widget, while this attempt returns a Future.
How I can fill the _messages array with data coming from my firestore collection on the initialization of my chat screen page?

Answer 1

If you just need to display all messages in a ListView from the firestore collection, then maybe you'll love the StreamBuilder widget. You can do something like this:
return new Column(
children: <Widget>[
new Flexible(
child: StreamBuilder(
stream: Firestore.instance.collection('chats').document('ROOM_1').collection('messages').snapshots(),
builder: (context, snapshot){
if (!snapshot.hasData){
return Container(
child: Center(
child: Text("No data")
)
);
}
return ListView.builder(
padding: EdgeInsets.all(8.0),
reverse: true,
itemCount: snapshot.data.documents.length,
itemBuilder: (_, int index) {
return ChatMessage(text: snapshot.data.documents[index]["messageField"]); //I just assumed that your ChatMessage class takes a parameter message text
}
);
}
)
),
new Divider(
height: 1.0,
),
...
Note that in this example, I didn't use the _messages variable.