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[英]Flutter Provider: MaterialApp.router depends on provider
[英]In Flutter MaterialApp, using Provider inside LocaleResolutionCallback has an error
在我的 flutter 項目中,我為 DI 選擇riverpod_hook
。
為了根據移動設備的語言設置更改應用程序的語言設置,我編寫了如下代碼。
// app.dart
import 'package:flutter/material.dart';
import 'package:hooks_riverpod/hooks_riverpod.dart';
class Application extends ConsumerWidget {
const Application({Key? key}) : super(key: key);
@override
Widget build(BuildContext context, WidgetRef ref) {
return MaterialApp(
theme: defaultTheme,
localizationsDelegates: Resource.localizationsDelegates,
supportedLocales: Resource.supportedLocales,
localeResolutionCallback: (Locale? locale, Iterable<Locale> supportedLocales) {
if (supportedLocales.any((element) => locale?.languageCode.contains(element.toString()) == true)) {
ref.watch(localeCodeProvider.notifier).state = locale!.languageCode;
return locale;
}
return const Locale('ko', '');
},
routes: {
homePageRoutes: (_) => const HomePage(),
detailPageRoutes: (_) => const DetailPage(),
},
);
}
}
import 'package:hooks_riverpod/hooks_riverpod.dart';
final localeCodeProvider = StateProvider<String>((ref) => 'en');
當我運行這段代碼時,發生了這個錯誤。
E/flutter ( 3747): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: Tried to modify a provider while the widget tree was building.
E/flutter ( 3747): If you are encountering this error, chances are you tried to modify a provider
E/flutter ( 3747): in a widget life-cycle, such as but not limited to:
E/flutter ( 3747): - build
E/flutter ( 3747): - initState
E/flutter ( 3747): - dispose
E/flutter ( 3747): - didUpdateWidget
E/flutter ( 3747): - didChangeDepedencies
E/flutter ( 3747):
E/flutter ( 3747): Modifying a provider inside those life-cycles is not allowed, as it could
E/flutter ( 3747): lead to an inconsistent UI state. For example, two widgets could listen to the
E/flutter ( 3747): same provider, but incorrectly receive different states.
E/flutter ( 3747):
E/flutter ( 3747):
E/flutter ( 3747): To fix this problem, you have one of two solutions:
E/flutter ( 3747): - (preferred) Move the logic for modifying your provider outside of a widget
E/flutter ( 3747): life-cycle. For example, maybe you could update your provider inside a button's
E/flutter ( 3747): onPressed instead.
E/flutter ( 3747):
E/flutter ( 3747): - Delay your modification, such as by encasuplating the modification
E/flutter ( 3747): in a `Future(() {...})`.
E/flutter ( 3747): This will perform your upddate after the widget tree is done building.
從報錯信息可以看出,錯誤的發生是因為build function內部使用了provider watch
。
但是,我不願意使用localeResolutionCallback
屬性,因為我想設置移動設備的語言設置值並設置整個應用程序的語言。
在這種情況下,我能否獲得有關如何使用provider
的適當解決方案?
嘗試調用 WidgetsBinding.instance.addPostFrameCallback 是否可行,如下所示:
if (supportedLocales.any((element) => locale?.languageCode.contains(element.toString()) == true)) {
WidgetsBinding.instance.addPostFrameCallback((_) {
ref.watch(localeCodeProvider.notifier).state =
locale!.languageCode;
});
return locale;
}
它的作用 - 它允許您完成構建; 然后更改提供者 - 這很可能會調用另一個構建。
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