chapter_13.4.md

13.4 Frequently Asked Questions about Internationalization

This section mainly answers common questions in internationalization.

The default locale is wrong

Some Android and iOS devices purchased from some non-mainland licensed channels will have the default Locale not Chinese simplified. This is a normal phenomenon, but in order to prevent the Locale obtained by the device from being inconsistent with the actual region, all apps that support multiple languages ​​must provide an entrance to manually select the language.

How to internationalize app titles

MaterialAppThere is an titleattribute to specify the title of the APP. In the Android system, the title of the APP will appear in the task manager. So it also needs to titlebe internationalized. But the problem is that many international configuration is in MaterialAppthe set, we can not build MaterialAppthrough Localizations.ofto get localized resources, such as:

MaterialApp(
 title: DemoLocalizations.of(context).title, //不能正常工作！
 localizationsDelegates: [
   // 本地化的代理类
   GlobalMaterialLocalizations.delegate,
   GlobalWidgetsLocalizations.delegate,
   DemoLocalizationsDelegate() // 设置Delegate
 ],
);

After running the above code, DemoLocalizations.of(context).titleit is being given, because Localizations.oflooks along widget from the current context to the top of the tree DemoLocalizations, but we are MaterialAppin complete set DemoLocalizationsDelegateafter, in fact, DemoLocalizationsin the current context of the sub-tree, it DemoLocalizations.of(context)will return null, Report an error. So how do we deal with this situation? It's actually very simple, we only need to set a onGenerateTitlecallback:

MaterialApp(
 onGenerateTitle: (context){
   // 此时context在Localizations的子树中
   return DemoLocalizations.of(context).title;
 },
 localizationsDelegates: [
   DemoLocalizationsDelegate(),
   ...
 ],
);

How to specify the same locale for English-speaking countries

There are many English-speaking countries, such as the United States, Britain, Australia, etc. Although these English-speaking countries speak English, there are some differences. If our APP only wants to provide one kind of English (such as American English) for all English-speaking countries to use, we can localeListResolutionCallbackdo compatibility in the previous introduction :

localeListResolutionCallback:
   (List<Locale> locales, Iterable<Locale> supportedLocales) {
 // 判断当前locale是否为英语系国家，如果是直接返回Locale('en', 'US')     
}