Flutter调研（3）-demo编写与小结

// main.dart
import ‘package:flutter/material.dart‘; //导入Material的UI组件库，来自谷歌，使展示更鲜明
import ‘home.dart‘;

void main() => runApp(MyApp());// 程序的入口，调用runApp()启动程序, "=>"是单行方法的简写

class MyApp extends StatelessWidget {
  // MyApp是一个继承于无状态statelessWidget的类
  @override
  Widget build(BuildContext context) {//调用build方法构建UI界面
    return MaterialApp( // 代表Material设计风格的应用，也是一个Widget，可定义应用名称，主题，首页
      title: ‘Flutter Demo mfw‘,// 任务管理窗口所展示的应用名称
      theme: ThemeData( //应用的主题颜色
        primarySwatch: Colors.blue,
      ),
      home: Home(title: ‘Flutter Demo Home Page‘),//应用默认所要展示的界面
    );
  }
}


// home.dart：一个计数器，三个跳转路由
class Home extends StatefulWidget {
  Home({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _HomeState createState() => _HomeState();
}


class _HomeState extends State<Home> {
  int _counter = 0;

  void _incrementCounter() {// 监控按钮的增加数值方法
    setState(() {//通知Flutter框架有状态改变，Flutter框架收到通知后，会执行build方法重新构建界面
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(

        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              ‘You have clicked the button this many times:‘,
            ),
            Text(
              ‘$_counter‘,
              style: Theme.of(context).textTheme.display1,
            ),

            FlatButton(
              child: Text("open new case1"),
              textColor: Colors.blue,
              onPressed: (){
                Navigator.push( context,
                    MaterialPageRoute(builder: (context){
                      return NewRoute();
                    }));
              },
            ),

          FlatButton(
            child: Text("open new case2"),
           textColor: Colors.blue,
           onPressed: (){
              Navigator.push( context,
            MaterialPageRoute(builder: (context){
              return NewRoute1();
            }));
      },
    ),

          FlatButton(
          child: Text("open new case3"),
      textColor: Colors.blue,
      onPressed: (){
        Navigator.push( context,
            MaterialPageRoute(builder: (context){
              return Route3();
            }));
      },
    )

          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: ‘Increment‘,
        child: Icon(Icons.add),
      ), 
    );
  }
}

// 每个widget继承自StatelessWidget或者StatefuleWidegt
// statelessWidget状态变化不大，statefulWidget分成两个，一个有build构建方法，一个继承自state类
// 一个标准statelessWidget的Widget构建过程如下
class  TestWidget extends StatelessWidegt{
@override
Widget build(BuildContext context){// build页面
return 控件名（
xxxx(child：内嵌其他控件
),
.....
）
}
}；
// 那么一个statefulWidget的构建过程
class Test extends StatefulWideget{
Route3({Key key}) : super(key: key);
@override
_TestState createState() => _TestState();  //新建state类
}


class _Route3State  extends State（Test）{
@override
Widget build(BuildContext context)// 在state类里build页面
....
}