编写第一个flutter应用

1.HelloWorld

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Welcome to Flutter',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('Welcome to Flutter'),
        ),
        body: new Center(
          child: new Text('Hello World'),
        ),
      ),
    );
  }
}

2.使用外部包

dependencies:
  flutter:
    sdk: flutter

  cupertino_icons: ^0.1.0
  english_words: ^3.1.0

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) {
    final wordPair = new WordPair.random();
    return new MaterialApp(
      title: 'Welcome to Flutter',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('Welcome to Flutter'),
        ),
        body: new Center(
          //child: new Text('Hello World'),
          child: new Text(wordPair.asPascalCase),
        ),
      ),
    );
  }
}

3.添加一个 有状态的部件（Stateful widget）

class RandomWords extends StatefulWidget {
  @override
  createState() => new RandomWordsState();
}
class RandomWordsState extends State<RandomWords> {
}
class RandomWordsState extends State<RandomWords> {
  @override
  Widget build(BuildContext context) {
    final wordPair = new WordPair.random();
    return new Text(wordPair.asPascalCase);
  }
}
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final wordPair = new WordPair.random();  // 删除此行

    return new MaterialApp(
      title: 'Welcome to Flutter',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('Welcome to Flutter'),
        ),
        body: new Center(
          //child: new Text(wordPair.asPascalCase),
          child: new RandomWords(),
        ),
      ),
    );
  }
}

4. 创建一个无限滚动ListView

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

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    // final wordPair = new WordPair.random();
    return MaterialApp(
      title: 'Welcome to Flutter',
      home: new RandomWords(),
    );
  }
}
class RandomWordsState extends State<RandomWords>{
  final _suggestions = <WordPair>[];
  final _biggerFont = const TextStyle(fontSize: 18.0);
  @override
  Widget build(BuildContext context){
    // final wordPair = new WordPair.random();
    // return new Text(wordPair.asPascalCase);
    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){
    return new ListTile(title: new Text(
      pair.asPascalCase, 
      style: _biggerFont,
      ),
      );
  }
}
class RandomWords extends StatefulWidget{
   @override
   createState() => new RandomWordsState();
}

5.添加交互

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

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    // final wordPair = new WordPair.random();
    return MaterialApp(
      title: 'Welcome to Flutter',
      home: new RandomWords(),
    );
  }
}
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){
    // final wordPair = new WordPair.random();
    // return new Text(wordPair.asPascalCase);
    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);
           }
         });
       }
      );
  }
}
class RandomWords extends StatefulWidget{
   @override
   createState() => new RandomWordsState();
}

6.导航到新页面

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

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    // final wordPair = new WordPair.random();
    return MaterialApp(
      title: 'Welcome to Flutter',
      home: new RandomWords(),
    );
  }
}
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){
    // final wordPair = new WordPair.random();
    // return new Text(wordPair.asPascalCase);
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Startup Name Generator'),
        actions: <Widget>[
          new IconButton(icon: new Icon(Icons.list), onPressed: _pushSaved),
        ],
      ),
      body: _buildSuggestions(),
    );
    
  }

  void _pushSaved(){
      Navigator.of(context).push(
        new MaterialPageRoute(
          builder: (context){
            final tiles = _saved.map(
              (pair){
                return new ListTile(title: new Text(
                  pair.asPascalCase, 
                  style: _biggerFont,
                  ),
                );
              },
            );
             final divided = ListTile.divideTiles(
                context: context,
                tiles: tiles,
                ).toList(); 

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

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

7.使用主题更改UI

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