flutter - 当我渲染我的子 Material 应用程序时，如何阻止我的更改通知程序提供程序重建我的父 Material 应用程序？

Question

我有一个返回 MaterialApp() 的应用程序类它的家设置为 TheSplashPage() .如果任何首选项发生更改，此应用程序会监听首选项通知程序。

然后在 TheSplashPage()我等待某些条件成立，如果成立，我会向他们展示我的嵌套 Material 应用程序。

旁注 :我在这里使用 Material 应用程序，因为它看起来更合乎逻辑，因为它具有父 Material 应用程序不应该具有的路由。而且一旦用户未经身份验证或断开连接，我希望整个嵌套应用程序关闭并显示另一个页面。这很好用!

但我的问题如下。两个应用都听 ThePreferencesProvider()所以当主题改变时，他们都会得到通知并重建。但这是一个问题，因为每当父 Material 应用程序重建时，它都会返回启动页面。所以现在我回到 TheSplashPage()每当我更改 TheSettingsPage() 上的设置时.

所以我的问题是如何阻止我的应用程序返回到 TheSplashPage()每当我更改设置时？

Main.dart

void main() {
  runApp(App());
}

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    SystemChrome.setEnabledSystemUIOverlays([]);

    return MultiProvider(
      providers: [
        ChangeNotifierProvider<PreferencesProvider>(create: (_) => PreferencesProvider()),
        ChangeNotifierProvider<ConnectionProvider>(
          create: (_) => ConnectionProvider(),
        ),
        ChangeNotifierProvider<AuthenticationProvider>(create: (_) => AuthenticationProvider()),
      ],
      child: Consumer<PreferencesProvider>(builder: (context, preferences, _) {
        return MaterialApp(
          home: TheSplashPage(),
          theme: preferences.isDarkMode ? DarkTheme.themeData : LightTheme.themeData,
          debugShowCheckedModeBanner: false,
        );
      }),
    );
  }
}

TheSplashPage.dart

class TheSplashPage extends StatelessWidget {
  static const int fakeDelayInSeconds = 2;

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
        future: Future.delayed(new Duration(seconds: fakeDelayInSeconds)),
        builder: (context, delaySnapshot) {
          return Consumer<ConnectionProvider>(
              builder: (BuildContext context, ConnectionProvider connectionProvider, _) {

            if (delaySnapshot.connectionState != ConnectionState.done ||
                connectionProvider.state == ConnectionStatus.uninitialized) return _buildTheSplashPage(context);

            if (connectionProvider.state == ConnectionStatus.none) return TheDisconnectedPage();

            return Consumer<AuthenticationProvider>(
                builder: (BuildContext context, AuthenticationProvider authenticationProvider, _) {
              switch (authenticationProvider.status) {
                case AuthenticationStatus.unauthenticated:
                  return TheRegisterPage();
                case AuthenticationStatus.authenticating:
                  return TheLoadingPage();
                case AuthenticationStatus.authenticated:
                  return MultiProvider(
                    providers: [
                      Provider<DatabaseProvider>(create: (_) => DatabaseProvider()),
                    ],
                    child: Consumer<PreferencesProvider>(
                        builder: (context, preferences, _) => MaterialApp(
                              home: TheGroupManagementPage(),
                              routes: <String, WidgetBuilder>{
                                TheGroupManagementPage.routeName: (BuildContext context) => TheGroupManagementPage(),
                                TheGroupCreationPage.routeName: (BuildContext context) => TheGroupCreationPage(),
                                TheGroupPage.routeName: (BuildContext context) => TheGroupPage(),
                                TheSettingsPage.routeName: (BuildContext context) => TheSettingsPage(),
                                TheProfilePage.routeName: (BuildContext context) => TheProfilePage(),
                                TheContactsPage.routeName: (BuildContext context) => TheContactsPage(),
                              },
                              theme: preferences.isDarkMode ? DarkTheme.themeData : LightTheme.themeData,
                              debugShowCheckedModeBanner: false,
                            )),
                  );
              }
            });
          });
        });
  }

TheSettingsPage.dart

Switch(
  value: preferences.isDarkMode,
  onChanged: (isDarkmode) => preferences.isDarkMode = isDarkmode,
),

Answer 1

你陷入了 XY 问题

这里真正的问题不是“我的小部件重建太频繁”，而是“当我的小部件重建时，我的应用程序返回到启动页面”。

解决方案不是阻止重建，而是更改您的 build方法来解决问题，这是我之前在此处详细介绍的内容:How to deal with unwanted widget build?

您遇到了与交叉链接问题相同的问题:您误用了 FutureBuilder .

不要 :

@override
Widget build(BuildContext context) {
  return FutureBuilder(
    // BAD: will recreate the future when the widget rebuild
    future: Future.delayed(new Duration(seconds: fakeDelayInSeconds)),
    ...
  );
}

做 :

class Example extends StatefulWidget {
  @override
  _ExampleState createState() => _ExampleState();
}

class _ExampleState extends State<Example> {
  // Cache the future in a StatefulWidget so that it is created only once
  final fakeDelayInSeconds = Future<void>.delayed(const Duration(seconds: 2));

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      // Rebuilding the widget no longer recreates the future
      future: fakeDelayInSeconds,
      ...
    );
  }
}