Step 5: Flutter Get Started codelab

main.dart

// Step 5: Add a lazily loading infinite scrolling ListView.
// Also, add a heart icon so users can favorite word pairings.
// Save the word pairings in the State class.
// Make the hearts tappable and save the favorites list in the
// State class.

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Startup Name Generator',
      home: new RandomWords(),
    );
  }
}

class RandomWords extends StatefulWidget {
  @override
  createState() => new RandomWordsState();
}

class RandomWordsState extends State<RandomWords> {
  final _suggestions = <WordPair>[];

  final _saved = new Set<WordPair>();

  final _biggerFont = const TextStyle(fontSize: 18.0);

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Startup Name Generator'),
      ),
      body: _buildSuggestions(),
    );
  }

  Widget _buildSuggestions() {
    return new ListView.builder(
      padding: const EdgeInsets.all(16.0),
      itemBuilder: (context, i) {
        if (i.isOdd) return new Divider();

        final index = i ~/ 2;
        if (index >= _suggestions.length) {
          _suggestions.addAll(generateWordPairs().take(10));
        }
        return _buildRow(_suggestions[index]);
      },
    );
  }

  Widget _buildRow(WordPair pair) {
    final alreadySaved = _saved.contains(pair);
    return new ListTile(
      title: new Text(
        pair.asPascalCase,
        style: _biggerFont,
      ),
      trailing: new Icon(
        alreadySaved ? Icons.favorite : Icons.favorite_border,
        color: alreadySaved ? Colors.red : null,
      ),
      onTap: () {
        setState(
          () {
            if (alreadySaved) {
              _saved.remove(pair);
            } else {
              _saved.add(pair);
            }
          }
        );
      },
    );
  }
}