Dart 如何为屏幕设置不同的主题

我创建了Friendly Chat app，想添加一个不同主题的新屏幕，但不起作用:-(

整个应用有Brightness.dark个主题:

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

class MyApp extends StatelessWidget {

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    print("build MaterialApp");
    return new MaterialApp(
      title: 'Friendly Chat',
      theme: kTheme,
      home: new ChatScreen(),
      routes: <String, WidgetBuilder>{
        SettingsScreen.PATH: (BuildContext context) => new SettingsScreen()
      },
    );
  }
}

final ThemeData kTheme = new ThemeData(
  primarySwatch: Colors.indigo,
  primaryColor: Colors.indigoAccent[100],
  primaryColorBrightness: Brightness.dark,
);

当用户单击按钮时，我会按下设置屏幕:

Map results = await Navigator.of(context).pushNamed(SettingsScreen.PATH);

在设置屏幕中，我更改了AppBar的backgroundColor和brightness，但新的/不同的brightness没有效果(更改backgroundColor工作)

class SettingsScreen extends StatefulWidget {

  @override
  State createState() => new SettingsScreenState();
}

class SettingsScreenState extends State<SettingsScreen> {

  @override
  Widget build(BuildContext context) {
    return new WillPopScope(
      onWillPop: _onWillPop,
      child: new Scaffold(
        appBar: new AppBar(
          title: new Text("Settings"),
          backgroundColor: Colors.amberAccent[700],
          brightness: Brightness.light,
        ),
      ),
    );
  }
}

如何将设置屏幕AppBar主题更改为浅色主题？

EDIT个

最后我想:

• 所有屏幕均采用深色AppBar背景色，标题和图标均为白色

• 设置屏幕(仅限)有一个浅AppBar背景色，带有深色标题和图标

Bonus points:如何为整个屏幕设置不同的主题，而不仅仅是AppBar