No MaterialLocalizations found.和No MediaQuery widget found的解决方法

在使用​​showDialog​​​和​​showModalBottomSheet​​​时，发现它们不能直接写在 ​​MaterialApp​​​的home属性下，会报如下错误：
​​​Another exception was thrown: No MaterialLocalizations found.​​​ 或
​​Another exception was thrown: No MediaQuery widget found.​​

解决的办法就是将代码提取出来：

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      /// [home]这个地方，不能直接写dialog的代码，否则你会得到 "Another exception was thrown: No MaterialLocalizations found."
      /// 也不能写showModalBottomSheet的代码，否则你会得到 Another exception was thrown: No MediaQuery widget found.
      /// 正确的做法就是把所有的内容都提取出去写。如下面这样把内容都提出来写到[HomePage]
      home: HomePage(),// 不能直接写dialog的代码
    );
  }
}

提取出来的代码放到HomePage下：

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('分享'),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.share),
            onPressed: () {
            showModalBottomSheet(
                  /**
               * showModalBottomSheet常用属性
               * shape 设置形状
               * isScrollControlled：全屏还是半屏
               * isDismissible：外部是否可以点击，false不可以点击，true可以点击，点击后消失
               * backgroundColor : 设置背景色
               */
                  backgroundColor: Colors.transparent,
                  context: context,
                  builder: (BuildContext context) {
                    return RaisedButton(
                      child: Text("Click"),
                      onPressed: () {},
                    );
                  },
                );
            },
          ),
        ],
      ),
      body: Center(),
    );
  }
}