Work with long lists
The standard ListView
constructor works well for small lists. To work with lists that contain
a large number of items, it’s best to use the
ListView.builder
constructor.
In contrast to the default ListView
constructor, which requires
creating all items at once, the ListView.builder()
constructor
creates items as they’re scrolled onto the screen.
1. Create a data source
First, you need a data source. For example, your data source might be a list of messages, search results, or products in a store. Most of the time, this data comes from the internet or a database.
For this example, generate a list of 10,000 Strings using the
List.generate
constructor.
final items = List<String>.generate(10000, (i) => "Item $i");
2. Convert the data source into widgets
To display the list of strings, render each String as a widget
using ListView.builder()
.
In this example, display each String on its own line.
ListView.builder(
itemCount: items.length,
itemBuilder: (context, index) {
return ListTile(
title: Text('${items[index]}'),
);
},
);
Complete example
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
void main() {
runApp(MyApp(
items: List<String>.generate(10000, (i) => "Item $i"),
));
}
class MyApp extends StatelessWidget {
final List<String> items;
MyApp({Key key, @required this.items}) : super(key: key);
@override
Widget build(BuildContext context) {
final title = 'Long List';
return MaterialApp(
title: title,
home: Scaffold(
appBar: AppBar(
title: Text(title),
),
body: ListView.builder(
itemCount: items.length,
itemBuilder: (context, index) {
return ListTile(
title: Text('${items[index]}'),
);
},
),
),
);
}
}