import 'package:flutter/material.dart';

void main() {
  runApp(new MyApp());
}

class Foo {
  final int value;
  Foo(this.value);
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(primarySwatch: Colors.blue),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<Foo> data;

  @override
  void initState() {
    super.initState();
    resetData();
  }

  void resetData() {
    data = <Foo>[];
    for (int i = 0; i < 30; ++i) {
      data.add(new Foo(i));
    }
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(title: new Text(config.title)),
      body: new Center(
        child: new ListView(
          children: data.map(_createListItemFromFoo).toList(),
        ),
      ),
    );
  }

  ListTile _createListItemFromFoo(Foo foo) {
    Key key = new ObjectKey(foo);  // Works fine without this object key.
    return new ListTile(
      key: key,
      title: new Text('Value: ${foo.value}'),
      onTap: () {
        setState(() {
          resetData();
        });
      },
    );
  }
}