Flutter笔记4：BottomAppBar底部应用栏和floatingActionButton实现中间凸起的底部导航

本文简单实现了通过BottomAppBar底部应用栏和floatingActionButton实现中间凸起的底部导航栏效果，底部应用栏（导航栏）除了BottomAppBar，还有BottomNavigationBar，这里采用BottomAppBar实现的效果：
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'BottomAppBar组件',
      home: Scaffold(
        appBar: AppBar(title: Text('BottomAppBar组件')),
        //设置FAB按钮的位置
        floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
        //FAB按钮
        floatingActionButton: FloatingActionButton(
          onPressed: () {},
          child: Icon(Icons.add),
        ),
        //底部导航栏，这里是 ButtomAppBar，定义更加灵活
        bottomNavigationBar: BottomAppBar(
            //设置FAB和底部导航栏buttomNigationBar的距离
            notchMargin: 10.0,
            color: Colors.pink,
            child: Container(
              height: 70.0,
              child: Row(
                //设置大小
                mainAxisSize: MainAxisSize.max,
                //设置间距
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                children: [
                  Column(
                    children: [
                      IconButton(icon: Icon(Icons.home), onPressed: () {}),
                      Text(
                        '首页',
                        style: TextStyle(fontSize: 12),
                      ),
                    ],
                  ),
                  Column(
                    children: [
                      IconButton(icon: Icon(Icons.search), onPressed: () {}),
                      Text(
                        '搜索',
                        style: TextStyle(fontSize: 12),
                      ),
                    ],
                  ),
                ],
              ),
            )),
      ),
    );
  }
}