如何监听 Flutter 中 platformBrightness 的变化？

我正在设置一个系统，当用户将系统主题更改为深色模式时，它会更改主题，并且使用 Flutter，它运行得很好！但是，当用户更改系统主题时，系统导航和状态栏不会改变其颜色。我在构建方法内的主页上运行了代码，但这似乎没有做到这一点。这是主页构建方法中的代码：

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    Brightness sysBrightness = MediaQuery.of(context).platformBrightness;
    if (sysBrightness == Brightness.dark)
      Themes.setDarkSystemColors();
    else
      Themes.setLightSystemColors();

    return Scaffold(
      appBar: CustomAppBar(title: "Home"),
      drawer: CustomDrawer(),
      body: SizedBox(),
    );
  }
}

这是主应用程序中的代码theme: and darkTheme::

    return MaterialApp(
      initialRoute: '/',
      routes: routes,
      navigatorObservers: [_routeObserver],
      theme: Themes.lightTheme,
      darkTheme: Themes.darkTheme,
      debugShowCheckedModeBanner: false,
      title: 'School Life',
    );

您可以通过多种方式做到这一点：

• Using didChangeDependencies

  // This callback will be invoked every time the platform brightness changes.
  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
  
    // Get the brightness. 
    var brightness = MediaQuery.of(context).platformBrightness;
  }
  

• Using WidgetsBindingObserver

  class _MyPageState extends State<MyPage> with WidgetsBindingObserver {
    @override
    void initState() {
      super.initState();
      WidgetsBinding.instance.addObserver(this);
    }
  
    // This callback is invoked every time the platform brightness changes. 
    @override
    void didChangePlatformBrightness() {
      super.didChangePlatformBrightness();
  
      // Get the brightness.
      var brightness = View.of(context).platformDispatcher.platformBrightness;
    }
  
    @override
    void dispose() {
      WidgetsBinding.instance.removeObserver(this);
      super.dispose();
    }
  
    @override
    Widget build(BuildContext context) => Container();
  }
  

• 设置监听器initState

  @override
  void initState() {
    super.initState();
  
    var dispatcher = SchedulerBinding.instance.platformDispatcher;
  
    // This callback is called every time the brightness changes. 
    dispatcher.onPlatformBrightnessChanged = () {
      var brightness = dispatcher.platformBrightness;
    };
  }