然后说一下这个，Flutter基础widgets教程-Scaffold篇

Scaffold({
  Key key,
  this.appBar, 
  this.body,undefined  this.floatingActionButton, 
  this.floatingActionButtonLocation, 
  this.floatingActionButtonAnimator, 
  this.persistentFooterButtons, 
  this.drawer, 
  this.endDrawer, 
  this.bottomNavigationBar,
  this.bottomSheet, 
  this.backgroundColor,
  this.resizeToAvoidBottomPadding = true, 
  this.primary = true,
}) 

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appBar: AppBar(
    title: Text(
        "Flutter Demo"
    ),
),

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body: Center(
    child: Text(
        'Hello Flutter'
    ),
),

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drawer: Drawer(
    child: Center(
        child: Text('Drawer'),
    ),
),

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bottomNavigationBar: new BottomNavigationBar(
    currentIndex: 1,//默认选中的位置
    fixedColor: Colors.green,//选中的颜色
    items:<BottomNavigationBarItem>
        new BottomNavigationBarItem(
            icon:new Icon(
                Icons.airplay,
            ),
            title: new Text(
                '主页',
            ),
         ),
         ......
     ,
),

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floatingActionButton: FloatingActionButton(
    onPressed: (){},
    child: Text('点击'),
),

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