How to append new ListView items at the top - flutter

Question

I am fetching ListView.builder() items from Cloud Firestore inside a StreamBuilder. I want the new item to be added at the top of the ListView. How can I do that? I tried reverse : true , though it reverse the ListView, but when there is only 2/3 items, the ListView looks ugly, as the ListView starts from bottom and the upper portion of the screen remains empty.

Answer 1

Added shrinkWrap: true and put the ListView inside an Align widget with alignment: Alignment.topCenter and got the result I wanted!
Align(
alignment: Alignment.topCenter,
child: ListView.builder(
reverse: true,
shrinkWrap: true,
...
...
)
)

Answer 2

if you want to add new item at the top of the the listview and if you are
using firestore used Timestamp
firebase. firestore. Timestamp
A Timestamp represents a point in time independent of any time zone
use this method
Timestamp.now()
fetch data from firestore order by time using StreamBuilder
Widget item() =>
StreamBuilder<QuerySnapshot>(
//fetch data from friends collection order by time
stream: Firestore.instance.collection("friends").orderBy(
"time", descending: true).snapshots(),
builder: (context, snapshot) {
//if data not exist show loading indicator
if (!snapshot.hasData)
return CircularProgressIndicator();
//if data exist
return ListView.builder(itemBuilder: (context, index) {
return Text(snapshot.data.documents[index].data['name']);
});
},
);
add data in firestore
Firestore.collection("friends")
.document(friends.otherUID)
.setData({"name" : "xyz","time": Timestamp.now()});
if you want to update item and you want to add updated item at the top of the listview
update data
Future<void> updatefriends({String name,Timestamp time}) async {
Map<String, Object> updateFriend = Map();
if (name.isNotEmpty) updateFriend['name'] = name;
if (time !=null) updateFriend['time']=time;
Firestore.instance.collection("friends")
.document(uid)
.updateData(updateFriend);
}

Answer 3

Just create a variable with the reverse index of the snapshots lenght, here is an example:
StreamBuilder(
stream: Firestore.instance.collection('news').snapshots(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (!snapshot.hasData) return Text('Loading...');
int reverseIndex = snapshot.data.documents.length;
return ListView.builder(
itemCount: snapshot.data.documents.length,
itemBuilder: (context, index) {
reverseIndex -=1;
return _buildItems(context, snapshot.data.documents[reverseIndex]);
});
}),

Answer 4

Keep in mind what comes first in your list, ie at the top, are the items that are in the first positions of your array. If the case, you can invert the array.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
List<int> Items = [5, 4, 3, 2, 1];
void _incrementItems() {
setState(() {
Items = List.from([9, 8, 7, 6])..addAll(Items);
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: ListView.builder(
itemCount: Items.length,
itemBuilder: (context, index) {
return Text(
"Item "+Items[index].toString());
},
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementItems,
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}

Answer 5

StoreConnector<_ViewModel, List<Message>>(
converter: (store) {
// check mark ,reverse data list
if (isReverse) return store.state.dialogList;
return store.state.dialogList.reversed.toList();
},
builder: (context, dialogs) {
// Add a callback when UI render after. then change it direction;
WidgetsBinding.instance.addPostFrameCallback((t) {
// check it's items could be scroll
bool newMark = _listViewController.position.maxScrollExtent > 0;
if (isReverse != newMark) { // need
isReverse = newMark; // rebuild listview
setState(() {});
}
});
return ListView.builder(
reverse: isReverse, // if it has less data, it will false now;
controller: _listViewController,
itemBuilder: (context, index) => _bubbleItem(context, dialogs[index], index),
itemCount: dialogs.length,
);
},
)