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修改2.1章节：去掉new标记，使用const以遵守新的规范 #449

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修改2.1章节：去掉new标记，使用const以遵守新的规范 #449

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修改2.1章节：去掉new标记，使用const以遵守新的规范
youran1024 Jun 25, 2021
dd70712
fix:修改错别字&简化语言
youran1024 Jun 25, 2021
821cbce
fix: 修改@required标记为 required
youran1024 Jun 28, 2021
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62 changes: 32 additions & 30 deletions src/chapter2/first_flutter_app.md
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Original file line number Diff line number Diff line change
Expand Up @@ -24,27 +24,28 @@
```dart
import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return new MaterialApp(
return MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Flutter Demo Home Page'),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}

class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
const MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;

@override
_MyHomePageState createState() => new _MyHomePageState();
State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
Expand All @@ -58,28 +59,28 @@ class _MyHomePageState extends State<MyHomePage> {

@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text(widget.title),
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: new Center(
child: new Column(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Text(
const Text(
'You have pushed the button this many times:',
),
new Text(
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: new FloatingActionButton(
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: new Icon(Icons.add),
child: const Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
Expand All @@ -100,7 +101,7 @@ class _MyHomePageState extends State<MyHomePage> {
2. 应用入口。

```dart
void main() => runApp(MyApp());
void main() => runApp(const MyApp());
```

- 与C/C++、Java类似，Flutter 应用中`main`函数为应用程序的入口。`main`函数中调用了`runApp` 方法，它的功能是启动Flutter应用。`runApp`它接受一个`Widget`参数，在本示例中它是一个`MyApp`对象，`MyApp()`是Flutter应用的根组件。
Expand All @@ -110,17 +111,18 @@ class _MyHomePageState extends State<MyHomePage> {

```dart
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return new MaterialApp(
return MaterialApp(
//应用名称
title: 'Flutter Demo',
theme: new ThemeData(
theme: ThemeData(
//蓝色主题
primarySwatch: Colors.blue,
),
//应用首页路由
home: new MyHomePage(title: 'Flutter Demo Home Page'),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
Expand All @@ -140,10 +142,10 @@ class _MyHomePageState extends State<MyHomePage> {

```dart
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
MyHomePage({Key? key, required this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => new _MyHomePageState();
State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
Expand Down Expand Up @@ -191,28 +193,28 @@ class _MyHomePageState extends State<MyHomePage> {

```dart
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text(widget.title),
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: new Center(
child: new Column(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Text(
const Text(
'You have pushed the button this many times:',
),
new Text(
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: new FloatingActionButton(
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: new Icon(Icons.add),
child: const Icon(Icons.add),
),
);
}
Expand Down
7 changes: 4 additions & 3 deletions src/chapter2/flutter_router.md
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Original file line number Diff line number Diff line change
Expand Up @@ -61,7 +61,7 @@
`MaterialPageRoute`继承自`PageRoute`类，`PageRoute`类是一个抽象类，表示占有整个屏幕空间的一个模态路由页面，它还定义了路由构建及切换时过渡动画的相关接口及属性。`MaterialPageRoute` 是Material组件库提供的组件，它可以针对不同平台，实现与平台页面切换动画风格一致的路由切换动画：

- 对于Android，当打开新页面时，新的页面会从屏幕底部滑动到屏幕顶部；当关闭页面时，当前页面会从屏幕顶部滑动到屏幕底部后消失，同时上一个页面会显示到屏幕上。
- 对于iOS，当打开页面时，新的页面会从屏幕右侧边缘一致滑动到屏幕左边，直到新页面全部显示到屏幕上，而上一个页面则会从当前屏幕滑动到屏幕左侧而消失；当关闭页面时，正好相反，当前页面会从屏幕右侧滑出，同时上一个页面会从屏幕左侧滑入。
- 对于iOS，当打开新页面时，新的页面会从屏幕右侧一直滑动，直到新页面全部显示到屏幕上，而上一个页面则会从当前屏幕滑动到屏幕左侧而消失；当关闭页面时，正好相反，当前页面会从屏幕右侧滑出，同时上一个页面会从屏幕左侧滑入。

下面我们介绍一下`MaterialPageRoute` 构造函数的各个参数的意义：

Expand Down Expand Up @@ -117,7 +117,7 @@ Navigator类中第一个参数为context的**静态方法**都对应一个Naviga
class TipRoute extends StatelessWidget {
TipRoute({
Key key,
@required this.text, // 接收一个text参数
required this.text, // 接收一个text参数
}) : super(key: key);
final String text;

Expand Down Expand Up @@ -353,4 +353,5 @@ MaterialApp(

综上所述，笔者比较建议使用命名路由，当然这并不是什么金科玉律，读者可以根据自己偏好或实际情况来决定。

另外，还有一些关于路由管理的内容我们没有介绍，比如路由MaterialApp中还有`navigatorObservers`和`onUnknownRoute`两个回调属性，前者可以监听所有路由跳转动作，后者在打开一个不存在的命名路由时会被调用，由于这些功能并不常用，而且也比较简单，我们便不再花费篇幅来介绍了，读者可以自行查看API文档。
另外，还有一些关于路由管理的内容我们没有介绍，比如路由MaterialApp中还有`navigatorObservers`和`onUnknownRoute`两个回调属性，前者可以监听所有路由跳转动作，后者在打开一个不存在的命名路由时会被调用，由于这些功能并不常用，而且也比较简单，我们便不再花费篇幅来介绍了，读者可以自行查看API文档。