flutter - 如何在单击 IconButton 时将主题更改为深色？

Question

在我的应用程序中，在 appBar 中，有一个按钮可以将主题更改为深色。我需要创建功能提供者。如何实现？我只需要将脚手架颜色更改为黑色，将文本颜色更改为白色。我的 main.dart:

Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        textTheme: const TextTheme(
          headline1: TextStyle(fontSize: 50.0, fontWeight: FontWeight.bold),
          headline5: TextStyle(fontSize: 36.0, fontStyle: FontStyle.italic),
          subtitle2: TextStyle(fontSize: 10.0, color: Colors.black),
          bodyText1: TextStyle(fontSize: 14.0, color: Colors.black),
        ),
      ),
      home: const HomeScreen(),
    );
  }

我的开关按钮:

appBar: AppBar(
        title: const Text('Flutter theme config'),
        centerTitle: true,
        actions: [
          IconButton(
            onPressed: () {

            },
            icon: const Icon(Icons.dark_mode),
          )
        ],
      ),

主题提供者:

class ThemeProvider extends ChangeNotifier {

}

Answer 1

你可以尝试这样的事情:

首先，我们为整个应用程序全局提供我们的 Provider，然后在属性 theme 中:我们监听变化。

** 主要 **

void main() async {
  runApp(
    MultiProvider( // create the provider
      providers: [
        ChangeNotifierProvider(
          create: (_) => ThemeProvider(),
        )
      ],
      child: const MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Material App',
      initialRoute: HomeScreen.routerName,
      routes: {
      },
      theme: Provider.of<ThemeProvider>(context).currentTheme, // listen to the current theme
    );
  }
}

在provider中我们只会有两个功能，一个切换到LightMode，另一个切换到DarkMode，然后我们把它添加到currentTheme 变量，它是在 ma​​in

中监听的变量

** 主题提供者 **

class ThemeProvider extends ChangeNotifier {
  ThemeData? currentTheme;

  setLightMode() {
    currentTheme = ThemeData(
      brightness: Brightness.light, // LightMode
      scaffoldBackgroundColor: Colors.red,
      [...] // more attributes
    );
    notifyListeners();
  }

  setDarkmode() {
    currentTheme = ThemeData(
      brightness: Brightness.dark, // DarkMode
      scaffoldBackgroundColor: Colors.green,
      [...] // more attributes
    );
    notifyListeners();
  }
}

最后我们创建一个StatefulWidget来改变isDarkMode变量来调用provider

** 按钮主页 **

class _HomeScreenState extends State<SettingsScreen> {
  bool isDarkmode = false; // new variable

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: const Text("Settings"),
        ),
        body: Padding(
          padding: const EdgeInsets.all(8.0),
          child: IconButton(
             onPressed: () {
               final themeProvider =
                        Provider.of<ThemeProvider>(context, listen: false); // get the provider, listen false is necessary cause is in a function

               setState(() {
                  isDarkmode = !isDarkmode;
               }); // change the variable

               isDarkmode // call the functions
                  ? themeProvider.setDarkmode()
                  : themeProvider.setLightMode();
             },
             icon: const Icon(Icons.dark_mode),
          ),
        ),
    );
  }
}