Colors.transparent,  //透明色
Colors.black.withOpacity(0.4)

new Image.asset('images/goods_image.png', width: 30.0, height: 30.0,),

floatingActionButton: new FloatingActionButton(
         tooltip: 'Add', // used by assistive technologies
         child: new Icon(Icons.add),
         // 点击进行页面跳转
         onPressed:() {
           goNextPage(context);
         }
         ),
   );

// 写法①
onPressed: null,

// 写法②：推荐
onPressed: () {}

// 写法③：不推荐
onPressed: () => {}
// 缺点：只能直接retrun返回值，不能写多行

// 设方法为：
void printLog() {
  print("This is printLog Method");
}

// 则按钮点击事件有两种写法：
// 写法①：常见的写法
onPressed: () {
    printLog();
},
// 写法②：简写
onPressed: printLog,

//设方法为：
void printText($text) {
  print("The text is " + $text);
}
//则按钮点击事件为：
onPressed:() {
	printText("Hello world");
}

import 'NewRoute.dart';

// 按钮处的写法
onPressed: () {
    Navigator.push(context, new MaterialPageRoute(builder: (context) {
        return new NewRoute();
    }));
},

import 'NewRoute.dart';

// 定义导航到新路由的方法
void goNextPage(context) {
  Navigator.push(context, new MaterialPageRoute(builder: (context) {
    return new NewRoute();
  }));
}

// 则按钮处的写法，自然如下：
onPressed:() {
    goNextPage(context);
}

import 'NewRoute.dart';

// 在MaterialApp中注册路由表
routes: {
    "new_page": (context) => NewRoute(),
},

// 按钮位置写法
onPressed: () {
    Navigator.pushNamed(context, "new_page");
},

import 'package:flutter/material.dart';

// 方法①
// >>>>>>>>>>>>> start >>>>>>>>>>>>>
// void main() => runApp(const Center(
//     child: Text('1.Hello, world! in Main', textDirection: TextDirection.ltr)));
// <<<<<<<<<<<<<  end  <<<<<<<<<<<<<


// 方法②
// >>>>>>>>>>>>> 方法② >>>>>>>>>>>>>
// void main() => runApp(MyApp());

// class MyApp extends StatelessWidget {
//   @override
//   Widget build(BuildContext context) {
//     return const Center(
//         child: Text('2.Hello, world! in MyApp return!', textDirection: TextDirection.ltr));
//   }
// }
// <<<<<<<<<<<<< 方法② <<<<<<<<<<<<<


// 方法③
// >>>>>>>>>>>>> 方法③ >>>>>>>>>>>>>
// void main() => runApp(MyApp());

// class MyApp extends StatelessWidget {
//    helloWorldPage() {
//      return Center(
//        child: Text('3.Hello world! in helloWorldPage',
//            textDirection: TextDirection.ltr),
//      );
//    }

//    @override
//    Widget build(BuildContext context) {
//      return helloWorldPage();
//  }
// }
// <<<<<<<<<<<<< 方法③ <<<<<<<<<<<<<


// 方法④
// >>>>>>>>>>>>> 方法④ >>>>>>>>>>>>>
void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return HelloWorldPage();
  }
}

class HelloWorldPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text('4.Hello world! in HelloWorldPage',
          textDirection: TextDirection.ltr),
    );
  }
}
// <<<<<<<<<<<<< 方法④ <<<<<<<<<<<<<

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

// 写法①
// >>>>>>>>>>>>> runApp写法① >>>>>>>>>>>>>
// void main() {
//   runApp(new MaterialApp(
//     title: '1.MaterialApp in main',
//     home: new HelloWorldPage(),
//   ));
// }
// <<<<<<<<<<<<< runApp写法① <<<<<<<<<<<<<


// 写法②
// >>>>>>>>>>>>> runApp写法② >>>>>>>>>>>>>
void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: '2.MaterialApp in MyApp',

      // 页面跳转的方式②：注册路由表
      // 详情查看[官网路由管理](https://book.flutterchina.club/chapter2/flutter_router.html)
      // 缺点：路由传递的参数无法动态修改(如果路由有参数)
      routes: {
        "new_page": (context) => NewRoute(),
      },

      home: HelloWorldPage(),
    );
  }
}
// <<<<<<<<<<<<< runApp写法② <<<<<<<<<<<<<


class HelloWorldPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //Scaffold是Material中主要的布局组件.
    return new Scaffold(
        appBar: new AppBar(
          leading: new IconButton(
            icon: new Icon(Icons.menu),
            tooltip: 'Navigation menu',
            onPressed: null,
          ),
          title: new Text('MaterialApp Example title'),
          actions: <Widget>[
            new IconButton(
              icon: new Icon(Icons.search),
              tooltip: 'Search',
              onPressed: null,
            ),
          ],
        ),
        //body占屏幕的大部分
        body: new Center(
          child: new Text('Hello, world2!'),
        ),
        floatingActionButton: new FloatingActionButton(
          tooltip: 'Add', // used by assistive technologies
          child: new Icon(Icons.add),
          // 1、无方法
          // 写法①
          // onPressed: null,
          // 写法②
          // onPressed: () {}
          // 写法③
          // onPressed: () => {}

          // 2、有方法，但该方法无参数
          // 写法①
          // onPressed: printLog,
          // 写法②
          // onPressed: () {
          //   printLog();
          // },

          // 3、有方法，且该方法有参数
          // onPressed:() {
          //   printText("Hello world");
          // }

          // 4.页面跳转方式
          // 写法①
          // onPressed: () {
          //   goNextPage(context);
          // },
          // 写法②
          // onPressed: () {
          //   Navigator.pushNamed(context, "new_page");
          // },
          // 写法③
          onPressed: () {
            Navigator.push(context, new MaterialPageRoute(builder: (context) {
              return new NewRoute();
            }));
          },
        )
    );
  }
}

void printLog() {
  print("This is printLog Method");
}

void printText($text) {
  print("The text is " + $text);
}

void goNextPage(context) {
  // 导航到新路由
  Navigator.push(context, new MaterialPageRoute(builder: (context) {
    return new NewRoute();
  }));
}

import 'package:flutter/material.dart';

class NewRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("New route"),
      ),
      body: Center(
        child: Text("This is new route"),
      ),
    );
  }
}

// 写法①
import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(
    title: '1.MaterialApp in main',
    home: new HelloWorldPage(),
  ));
}


// ------------------- 我是分割线，下面介绍的是另一种写法 ------------------- //
// 写法②
import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: '2.MaterialApp in MyApp',
      home: HelloWorldPage(),
    );
  }
}

import 'package:flutter/material.dart';

class NewRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("New route"),
      ),
      body: Center(
        child: Text("This is new route"),
      ),
    );
  }
}

class HelloWorldPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //Scaffold是Material中主要的布局组件.
    return new Scaffold(
      appBar: new AppBar(
        leading: new IconButton(
          icon: new Icon(Icons.menu),
          tooltip: 'Navigation menu',
          onPressed: null,
        ),
        title: new Text('MaterialApp Example title'),
        actions: <Widget>[
          new IconButton(
            icon: new Icon(Icons.search),
            tooltip: 'Search',
            onPressed: null,
          ),
        ],
      ),
      //body占屏幕的大部分
      body: new Center(
        child: new Text('Hello, world2!'),
      ),
      floatingActionButton: new FloatingActionButton(
        tooltip: 'Add', // used by assistive technologies
        child: new Icon(Icons.add),
        onPressed: null,
      ),
    );
  }
}

import 'package:flutter/material.dart';

class NewRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("New route"),
      ),
      body: Center(
        child: Text("This is new route"),
      ),
    );
  }
}