本文是官方文档学习过程的笔记
初始化项目
# bash
flutter create myapp
cd myapp
flutter run -d <deviceID>
Hello World
编写lib/main.dart， 然后在终端按“r”， 刷新app
import "package:flutter/material.dart";
void main() => runApp(new MyApp());
// StatelessWidget 组件是内部没有可变状态的组件，相当于React-Redux的展示组件
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: "Welcom to Flutter",
// new Scaffold(), 页面构造器，返回一个拥有appBar，和body的组件
// 有点类似iOS的 ViewController
home: new Scaffold(
appBar: new AppBar(
title: new Text("Welcom To Flutter"),
),
body: new Center(
child: new Text("hello world"),
),
)
);
}
}
我们会得到下面这个页面
Hello world
使用/添加第三方依赖
在pubspec.yaml中加入english_words依赖：
dependencies:
flutter:
sdk: flutter
# The following adds the Cupertino Icons font to your application.
# Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^0.1.2
english_words: ^3.1.0
执行命令下载安装依赖(需要科学上网)：
# bash
flutter packages get
修改main.dart：
import "package:flutter/material.dart";
// 添加依赖
import "package:english_words/english_words.dart";
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
// 随机生成一个wordPair文字
final wordPair = new WordPair.random();
return new MaterialApp(
title: "Welcom to Flutter",
home: new Scaffold(
appBar: new AppBar(
title: new Text("Welcom To Flutter"),
),
body: new Center(
// 使用wordPair生成的文字
child: new Text(wordPair.asPascalCase),
),
)
);
}
}
此时，每次刷新app，都会得到不同的文字， 这一段主要是讲解了如何引用和使用第三方包
创建ListView
import "package:flutter/material.dart";
import "package:english_words/english_words.dart";
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
// build方法相当于React的render函数
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: "Welcom to Flutter",
home: new RandomWords(),
);
}
}
// 这里使用了StatefulWidget组件，相当于React-Redux的容器组件
// 组件内部有状态可以维护
class RandomWords extends StatefulWidget{
@override
State<StatefulWidget> createState() {
return new RandomWordsState();
}
}
class RandomWordsState extends State<RandomWords> {
final _words = <WordPair>[];
final _biggerFont = const TextStyle(fontSize: 18.0);
Widget _buildWords(){
return new ListView.builder(
padding: const EdgeInsets.all(16.0),
itemBuilder: (context,i){
// 如果是奇数就返回一条分割线
if (i.isOdd) return new Divider();
// i ~/ 2 向下取整
final index = i ~/ 2 ;
if(index >= _words.length) {
// 往_words数组里添加10个字符对象
_words.addAll(generateWordPairs().take(10));
}
return _buildRow(_words[index]);
},
);
}
Widget _buildRow(WordPair pair) {
return new ListTile(
title: new Text(
pair.asPascalCase,
style: _biggerFont,
),
);
}
// State组件内部也需要重载build方法，build方法相当于React的render函数
@override
Widget build(BuildContext context){
return new Scaffold(
appBar: new AppBar(
title: new Text("Startup Name Generator"),
),
body: _buildWords(),
);
}
}
添加点击事件
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: "Welcom to Flutter",
home: new RandomWords(),
);
}
}
class RandomWords extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return new RandomWordsState();
}
}
class RandomWordsState extends State<RandomWords> {
final _words = <WordPair>[];
final _biggerFont = const TextStyle(fontSize: 18.0);
final _saved = new Set<WordPair>();
Widget _buildWords() {
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 >= _words.length) {
_words.addAll(generateWordPairs().take(10));
}
return _buildRow(_words[index]);
},
);
}
Widget _buildRow(WordPair pair) {
// 校验 _saved 是否包含pair对象
final isSaved = _saved.contains(pair);
return new ListTile(
title: new Text(
pair.asPascalCase,
style: _biggerFont,
),
// cell 尾部组件, 设置为一个Icon
trailing: new Icon(
isSaved ? Icons.favorite : Icons.favorite_border,
color: isSaved ? Colors.red : null,
),
// 当点击cell时，移除或添加当前行的title进_saved
onTap: () {
setState(() {
if (isSaved) {
_saved.remove(pair);
} else {
_saved.add(pair);
}
});
},
);
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text("Startup Name Generator"),
),
body: _buildWords(),
);
}
}
如图，可以渲染了列表，并且点击cell，表尾部的Icon会切换颜色
页面跳转
给appBar添加一个actions，并且创建一个IconButton，点击使用Navigator推进一个Scaffold组件
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: "Welcom to Flutter",
home: new RandomWords(),
);
}
}
class RandomWords extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return new RandomWordsState();
}
}
class RandomWordsState extends State<RandomWords> {
final _words = <WordPair>[];
final _biggerFont = const TextStyle(fontSize: 18.0);
final _saved = new Set<WordPair>();
Widget _buildWords() {
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 >= _words.length) {
_words.addAll(generateWordPairs().take(10));
}
return _buildRow(_words[index]);
},
);
}
Widget _buildRow(WordPair pair) {
final isSaved = _saved.contains(pair);
return new ListTile(
title: new Text(
pair.asPascalCase,
style: _biggerFont,
),
trailing: new Icon(
isSaved ? Icons.favorite : Icons.favorite_border,
color: isSaved ? Colors.red : null,
),
onTap: () {
setState(() {
if (isSaved) {
_saved.remove(pair);
} else {
_saved.add(pair);
}
});
},
);
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text("Startup Name Generator"),
actions: <Widget>[
new IconButton(
icon: new Icon(Icons.list),
onPressed: () {
// 实现页面跳转的函数
Navigator
.of(context)
.push(new MaterialPageRoute(builder: (context) {
return new SavedPage(saved: _saved, biggerFont: _biggerFont);
}));
},
)
]),
body: _buildWords(),
);
}
}
// 实现已保存数据的页面
class SavedPage extends StatelessWidget {
// 声明类的参数
SavedPage({@required this.saved, @required this.biggerFont});
final Set<WordPair> saved;
final TextStyle biggerFont;
// 渲染一个列表
@override
Widget build(BuildContext context) {
final divided = ListTile
.divideTiles(
context: context,
tiles: saved.map((pair) {
return new ListTile(
title: new Text(
pair.asPascalCase,
style: biggerFont,
),
);
}),
)
.toList();
return new Scaffold(
appBar: new AppBar(
title: new Text("Saved Words"),
),
body: new ListView(children: divided),
);
}
}
如下图Gif， 页面已经可以导航了
修改主题
MaterialApp里面有theme属性，可以设置全局主题
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: "Welcom to Flutter",
// 这里设置主题
theme: new ThemeData(
primaryColor: Colors.green,
dividerColor: Colors.greenAccent,
),
home: new RandomWords(),
);
}
}
如图，替换了主色和分割线的颜色
green主题
您已经编写了一个可在iOS和Android上运行的交互式Flutter应用程序。在这个codelab中，你应该已学到了：
- 从头开始创建一个Flutter应用程序。
- 书面Dart代码。
- 利用外部的第三方库。
- 使用热重载加快开发周期。
- 实现一个有状态的小部件，为你的应用增加交互性。
- 用ListView和ListTiles创建一个延迟加载的无限滚动列表。
- 实现了页面跳转
- 了解如何使用主题更改应用UI的外观。
至此，flutter官方快速入门文档已结束
