efortuna

import 'package:flutter/material.dart';
import 'package:flutter/gestures.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(title: 'Flutter Demo Home Page'),

efortuna

void main() => runApp(new MaterialApp(home: PositionedTiles()));

class PositionedTiles extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => PositionedTilesState();
}

class PositionedTilesState extends State<PositionedTiles> {
  List<Widget> tiles = [
    Padding(

efortuna

void main() => runApp(new MaterialApp(home: PositionedTiles()));

class PositionedTiles extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => PositionedTilesState();
}

class PositionedTilesState extends State<PositionedTiles> {
  // Stateful tiles now wrapped in padding (a stateless widget) to increase height 
  // of widget tree and show why keys are needed at the Padding level.

efortuna

List<Widget> tiles = [
  StatefulColorfulTile(key: UniqueKey()), // Keys added here
  StatefulColorfulTile(key: UniqueKey()),
];

...
class StatefulColorfulTile extends StatefulWidget {
  StatefulColorfulTile({Key key}) : super(key: key);  // NEW CONSTRUCTOR
 
  @override

efortuna

List<Widget> tiles = [
   StatefulColorfulTile(),
   StatefulColorfulTile(),
];

...
class StatefulColorfulTile extends StatefulWidget {
 @override
 ColorfulTileState createState() => ColorfulTileState();
}

efortuna

void main() => runApp(new MaterialApp(home: PositionedTiles()));

class PositionedTiles extends StatefulWidget {
 @override
 State<StatefulWidget> createState() => PositionedTilesState();
}

class PositionedTilesState extends State<PositionedTiles> {
 List<Widget> tiles = [
   StatelessColorfulTile(),

efortuna

class WikipediaExplorer extends StatefulWidget {
  @override
  _WikipediaExplorerState createState() => _WikipediaExplorerState();
}

class _WikipediaExplorerState extends State<WikipediaExplorer> {
  Completer<WebViewController> _controller = Completer<WebViewController>();
  final Set<String> _favorites = Set<String>();

  @override