我的应用程序主页上有一个 FutureBuilder，它在未来完成后返回一个 SliverFixedExtentList。它看起来像这样：
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:project_spruce/DataBase/DataBaseConnection.dart';
import 'package:project_spruce/states/UserState.dart';
import 'package:project_spruce/widgets/FabBottomAppBar.dart';
import 'package:project_spruce/widgets/FoodItemCard.dart';
import 'package:provider/provider.dart';
class HomeScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
final List<DocumentSnapshot> _documents = List<DocumentSnapshot>();
String uid = Provider.of<UserState>(context).firebaseUser.uid;
return FutureBuilder(
future: Provider.of<DataBaseConnection>(context).getQuerySnapshot('eatenFoods/'+ uid +'/food'),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot){
Widget child;
if (snapshot.hasData){
_documents.clear();
snapshot.data.documents.forEach((doc)=> _documents.add(doc));
child = SliverFixedExtentList(
itemExtent: 150,
delegate: new SliverChildBuilderDelegate(
(context, index) => FoodItemCard(_documents[index]),
childCount: _documents.length,
),
);
}else {
child = SliverToBoxAdapter(child: CircularProgressIndicator());
}
return Scaffold(
floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
floatingActionButton: FloatingActionButton(
onPressed: () => Navigator.pushNamed(context, '/camera_screen'),
tooltip: 'Add',
elevation: 2,
child: Icon(Icons.add),
backgroundColor: Theme.of(context).primaryColor,
foregroundColor: Colors.white,
),
bottomNavigationBar: FabBottomAppBar(
backgroundColor: Theme.of(context).primaryColor,
color: Colors.white,
selectedColor: Colors.white,
iconSize: 30,
notchedShape: CircularNotchedRectangle(),
items: [
FabBottomAppBarItem(iconData: Icons.search, text: 'Search'),
FabBottomAppBarItem(iconData: Icons.pie_chart, text: 'Statistics'),
FabBottomAppBarItem(
iconData: Icons.storage, text: 'Food Inventory'),
FabBottomAppBarItem(iconData: Icons.person, text: 'Profile'),
],
onTabSelected: (int tabIndex) {
switch (tabIndex) {
case 0:
{
// Search
Navigator.pushNamed(context, '/search');
}
break;
case 1:
{
// Statistics
Navigator.pushNamed(context, '/stats');
}
break;
case 2:
{
// Inventory
Navigator.pushNamed(context, '/inventory');
}
break;
case 3:
{
// Profile
Navigator.pushNamed(context, '/profile');
}
break;
}
},
),
body: new CustomScrollView(
slivers: <Widget>[
SliverAppBar(
//title: const Text('Home Page'),
actions: <Widget>[
IconButton(
icon: const Icon(Icons.notifications),
tooltip: 'Notifications',
onPressed: () => (){}, //(Navigator.pushNamed(context, '/notifications')),
),
],
floating: true,
pinned: true,
snap: false,
forceElevated: true,
expandedHeight: 200.0,
flexibleSpace: FlexibleSpaceBar(
title:
Text("Hi, " + Provider.of<UserState>(context).user.name),
centerTitle: false,
),
),
child,
],
)
);
}
);
}
}
Future 从数据库中获取文档列表，然后将它们按顺序传递给将数据包装在 Card 中的辅助类。问题是这个实现将最新的文档放在底部，而我希望它们放在顶部。我可以更改从数据库中检索文档的顺序Firestore.instance.collection(path).orderBy('date', descending: true).getDocuments();，但是由于每次返回页面时列表都不会完全重建，因此除非我重建应用程序，否则新数据根本不会显示。我还尝试reverse: true在自定义滚动视图中进行设置，但这会反转所有内容，包括 SliverAppBar。
有什么方法可以翻转 SliverFixedExtentList 的构建方式，以便更高的索引位于顶部？