如何订购Firebase文件? [英] How to order the documents of firebase?
问题描述
我想创建一个聊天应用程序，我也使用过Firebase，但是我无法在发送消息时将文档排序与随机出现的列表顺序不一致的情况下对文档进行排序.
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.
我认为这与firebase控制台中的文档类型相关(如果相关)，我希望获得有关如何在收到新消息时对其进行排序的帮助，该消息将位于列表的底部，反之亦然.
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.
我尝试了listview和listview.builder，并且使用了reverse属性，但是它对我不起作用.
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),
),
)),
],
),
);
}
}
推荐答案
Cloud Firestore中没有文档的隐式排序.
There is no implicit ordering for documents in Cloud Firestore.
如果要按特定顺序显示结果，则必须确保每个文档都包含必要的信息以确定其顺序.通常，这意味着您将在字段中添加创建文档的时间戳.
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.
有了这样的字段，您就可以使用orderBy()以特定的顺序检索文档:
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()
这篇关于如何订购Firebase文件?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
