Hello World Flutter / Dart

main.dart

import 'package:flutter/cupertino.dart'; // importa todas las funciones sin prefix
// import 'package:flutter/cupertino.dart' as cupertino; // go-style use cupertino.runApp(...

void main(){
  runApp(
    Center(
      child: Text(
        'Hello World',
      ), // Text
    )
  );
}

main_app_company_names.dart

import 'package:flutter/material.dart'; // importa todas las funciones sin prefix
// import 'package:flutter/cupertino.dart' as cupertino; go-style
import 'package:english_words/english_words.dart' as words;

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Trakting',
      // Scaffold es un widge tocn barra de titulo y otras cosas
      home: RandomWords(),
      theme: ThemeData(
        primaryColor: Colors.green
      ),
    );
  }
}

class RandomWords extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return RandomWordsState();
  }
}

class RandomWordsState extends State<RandomWords> {
  final _suggestions = <words.WordPair>[];
  final _saved = Set<words.WordPair>();
  final _textStyle = TextStyle(fontSize: 18.0);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Welcome to flutter'),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.list),
            onPressed: _pushSaved,
          )
        ],
      ),
      body: _buildSuggestions(),
    );
  }

  _pushSaved() {
    Navigator.of(context).push(MaterialPageRoute(builder: (context) {
      final tiles = _saved.map((pair) {
        return ListTile(
          title: Text(
            pair.asPascalCase,
            style: _textStyle,
          ),
        );
      });

      final divaded =
          ListTile.divideTiles(tiles: tiles, context: context).toList();

      return Scaffold(
        appBar: AppBar(
          title: Text('Saved'),
        ),
        body: ListView(children: divaded,)
      );
    }));
  }

  Widget _buildSuggestions() {
    return ListView.builder(
        padding: const EdgeInsets.all(16.0),
        itemBuilder: (context, index) {
          if (index.isOdd) {
            return Divider();
          }
          if (index >= _suggestions.length) {
            // llego al final
            _suggestions.addAll(words.generateWordPairs().take(10));
          }
          final indexWithDivider = index ~/ 2;
          return _buildRow(_suggestions[index]);
        });
  }

  Widget _buildRow(words.WordPair pair) {
    final isSaved = _saved.contains(pair);
    return ListTile(
      title: Text(
        pair.asPascalCase,
        style: _textStyle,
      ),
      trailing: Icon(
        isSaved ? Icons.favorite : Icons.favorite_border,
        color: isSaved ? Colors.red : Colors.blueGrey.shade100,
      ),
      onTap: () {
        setState(() {
          if (isSaved) {
            _saved.remove(pair);
          } else {
            _saved.add(pair);
          }
        });
      },
    );
  }
}