问题
I want to create a chat app, I have used firebase as well but I can't order documents where when you send a message it doesn't be with the order of the list it goes in a random place.
I think this is related to the sort of documents in firebase console if related I want help on how to sort this when a new message comes it will be at the bottom of the list and vice versa.
I have tried listview and listview.builder and I have used the reverse property but it didn't work with me .
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import '../constants.dart';
final _firestore = Firestore.instance;
FirebaseUser loggedInUser;
class ChatScreen extends StatefulWidget {
static String routeName = 'chat_screen';
@override
_ChatScreenState createState() => _ChatScreenState();
}
class _ChatScreenState extends State<ChatScreen> {
final messageTextController = TextEditingController();
final _auth = FirebaseAuth.instance;
String message;
void getCurrentUser() async {
try {
final user = await _auth.currentUser();
if (user != null) {
loggedInUser = user;
}
} catch (e) {
print(e);
}
}
void getMessages() async {
final messages = await _firestore.collection('message').getDocuments();
for (var message in messages.documents) {
print(message.data);
}
}
void messagesStream() async {
await for (var snapshot in _firestore.collection('messages').snapshots()) {
for (var message in snapshot.documents) {
print(message.data);
}
}
}
@override
void initState() {
super.initState();
getCurrentUser();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
leading: null,
actions: <Widget>[
IconButton(
icon: Icon(Icons.close),
onPressed: () {
_auth.signOut();
Navigator.pop(context);
}),
],
title: Text('⚡️Chat'),
backgroundColor: Colors.lightBlueAccent,
),
body: SafeArea(
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
MessagesStream(),
Container(
decoration: kMessageContainerDecoration,
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Expanded(
child: TextField(
controller: messageTextController,
onChanged: (value) {
message = value;
},
decoration: kMessageTextFieldDecoration,
),
),
FlatButton(
onPressed: () {
messageTextController.clear();
_firestore
.collection('messages')
.add({'text': message, 'sender': loggedInUser.email});
},
child: Text(
'Send',
style: kSendButtonTextStyle,
),
),
],
),
),
],
),
),
);
}
}
class MessagesStream extends StatelessWidget {
@override
Widget build(BuildContext context) {
return StreamBuilder<QuerySnapshot>(
stream: _firestore.collection('messages').snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return Center(
child: CircularProgressIndicator(
backgroundColor: Colors.lightBlueAccent,
),
);
}
final messages = snapshot.data.documents;
List<MessageBubble> messageBubbles = [];
for (var message in messages) {
final messageText = message.data['text'];
final messageSender = message.data['sender'];
final currentUser = loggedInUser.email;
final messageBubble = MessageBubble(
sender: messageSender,
text: messageText,
isMe: currentUser == messageSender);
messageBubbles.add(messageBubble);
}
return Flexible(
child: ListView.builder(
itemCount: messages.length,
itemBuilder: (context , index){
return MessageBubble(
isMe: loggedInUser.email == messages[index].data['sender'],
text: messages[index].data['text'],
sender: messages[index].data['sender'],
);
},),
);
},
);
}
}
class MessageBubble extends StatelessWidget {
MessageBubble({this.sender, this.text, this.isMe});
final bool isMe;
final String sender;
final String text;
@override
Widget build(BuildContext context) {
return Padding(
padding: EdgeInsets.all(10.0),
child: Column(
crossAxisAlignment:
isMe ? CrossAxisAlignment.end : CrossAxisAlignment.start,
children: <Widget>[
Text(sender, style: TextStyle(fontSize: 12, color: Colors.black54)),
Material(
elevation: 5.0,
borderRadius: isMe
? BorderRadius.only(
topLeft: Radius.circular(30),
bottomLeft: Radius.circular(30),
topRight: Radius.circular(30),
)
: BorderRadius.only(
bottomLeft: Radius.circular(30),
topRight: Radius.circular(30),
bottomRight: Radius.circular(30)),
color: isMe ? Colors.lightBlueAccent : Colors.white,
child: Padding(
padding: EdgeInsets.symmetric(vertical: 10, horizontal: 20),
child: Text(
text,
style: TextStyle(
color: isMe ? Colors.white : Colors.black54,
fontSize: 15),
),
)),
],
),
);
}
}
回答1:
Add order by
void getMessages() async {
final messages = await _firestore.collection('message').orderBy("created_at", descending: true).getDocuments();
for (var message in messages.documents) {
print(message.data);
}
}
void messagesStream() async {
await for (var snapshot in _firestore.collection('messages').orderBy("created_at", descending: true).snapshots()) {
for (var message in snapshot.documents) {
print(message.data);
}
}
}
回答2:
There is no implicit ordering for documents in Cloud Firestore.
If you want to show the results in a specific order, you will have to make sure each document includes the necessary information to determine its order. Typically this means that you include a field with the timestamp of when the document was created.
With such a field in place, you can then use orderBy() to retrieve the documents in a specific order:
await _firestore.collection('message').orderBy('timestamp').getDocuments()
回答3:
Check This out, perfectly running for a group chat app(if you want to get data from firebase).
class MessageStream extends StatelessWidget {
@override
Widget build(BuildContext context) {
return StreamBuilder<QuerySnapshot>(
stream: _firestore.collection("messages").orderBy("time").snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return Center(
child: CircularProgressIndicator(
backgroundColor: Colors.amber,
),
);
}
final messages = snapshot.data.documents.reversed;
List<MessageBubble> messageBubbles = [];
for (var message in messages) {
final messageText = message.data["text"];
final messageSender = message.data["sender"];
final messageTime = message.data["time"];
final currentUser = loggedInUser.email;
final messageBubble = MessageBubble(
sender: messageSender,
text: messageText,
isMe: currentUser == messageSender,
time: messageTime,
);
messageBubbles.add(messageBubble);
}
return Expanded(
child: ListView(
reverse: true,
padding: EdgeInsets.all(10),
children: messageBubbles,
),
);
},
);
}
}
来源：https://stackoverflow.com/questions/58491785/how-to-order-the-documents-of-firebase