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This is source code for a blog post.
import 'dart:async';
import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
theme: new ThemeData(primarySwatch: Colors.blue),
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
List<int> items = List.generate(10, (i) => i);
ScrollController _scrollController = new ScrollController();
bool isPerformingRequest = false;
@override
void initState() {
super.initState();
_scrollController.addListener(() {
if (_scrollController.position.pixels ==
_scrollController.position.maxScrollExtent) {
_getMoreData();
}
});
}
@override
void dispose() {
_scrollController.dispose();
super.dispose();
}
_getMoreData() async {
if (!isPerformingRequest) {
setState(() => isPerformingRequest = true);
List<int> newEntries = await fakeRequest(
items.length, items.length + 10); //returns empty list
if (newEntries.isEmpty) {
double edge = 50.0;
double offsetFromBottom = _scrollController.position.maxScrollExtent -
_scrollController.position.pixels;
if (offsetFromBottom < edge) {
_scrollController.animateTo(
_scrollController.offset - (edge - offsetFromBottom),
duration: new Duration(milliseconds: 500),
curve: Curves.easeOut);
}
}
setState(() {
items.addAll(newEntries);
isPerformingRequest = false;
});
}
}
Widget _buildProgressIndicator() {
return new Padding(
padding: const EdgeInsets.all(8.0),
child: new Center(
child: new Opacity(
opacity: isPerformingRequest ? 1.0 : 0.0,
child: new CircularProgressIndicator(),
),
),
);
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: AppBar(
title: Text("Infinite ListView"),
),
body: ListView.builder(
itemCount: items.length + 1,
itemBuilder: (context, index) {
if (index == items.length) {
return _buildProgressIndicator();
} else {
return ListTile(title: new Text("Number $index"));
}
},
controller: _scrollController,
),
);
}
}
/// from - inclusive, to - exclusive
Future<List<int>> fakeRequest(int from, int to) async {
return Future.delayed(Duration(seconds: 2), () {
return List.generate(to - from, (i) => i + from);
});
}
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