Localization
English is only one of many languages people speak around the world (thanks a lot, Tower of Babel) and it's polite and sometimes even necessary to translate our app to the languages our users speak. Let's look at one way we can do this in React Navigation - it's not the only way but it'll do the trick. Similar to themes, we will use React's context API in order to make it easier to access the translate function from a variety of components.
Setting up a localization library
We'll need to use some kind of library to store our translations and provide a function that gives us access to them, along with handling fallbacks when we don't have a particular language defined. Localization and internationalization (i18n) are often used interchangeably, as in the example below where we get the current locale
from expo-localization
and use the i18n-js
library for managing translations, for no particular reason other than it was available - use whatever you like.
import * as Localization from 'expo-localization'; // or whatever library you wantimport i18n from 'i18n-js'; // or whatever library you want
const en = { foo: 'Foo', bar: 'Bar {{someValue}}',};
const fr = { foo: 'Fou', bar: 'Bár {{someValue}}',};
i18n.fallbacks = true;i18n.translations = { fr, en };
// This will log 'en' for me, as I'm an English speakerconsole.log(Localization.locale);
Wiring up your localization library to navigation
Next let's store our locale
in the state of our root app component and then thread it through LocalizationContext
to make it available throughout our app.
export const LocalizationContext = React.createContext();
export default function App() { const [locale, setLocale] = React.useState(Localization.locale); const localizationContext = React.useMemo( () => ({ t: (scope, options) => i18n.t(scope, { locale, ...options }), locale, setLocale, }), [locale] );
return ( <LocalizationContext.Provider value={localizationContext}> <NavigationContainer>{/* Screen configuration */}</NavigationContainer> </LocalizationContext.Provider> );}
Now in our screens we can use these LocalizationContext
as follows:
function MyScreen() { const { t, locale, setLocale } = React.useContext(LocalizationContext);
return ( <View style={styles.container}> <Text style={styles.text}> Current locale: {locale}.{' '} {locale !== 'en' && locale !== 'fr' ? 'Translations will fall back to "en" because none available' : null} </Text> <Text>{t('bar', { someValue: Date.now() })}</Text> {locale === 'en' ? ( <Button title="Switch to French" onPress={() => setLocale('fr')} /> ) : ( <Button title="Switch to English" onPress={() => setLocale('en')} /> )} </View> );}
We can also use it for screen options:
function MyStack() { const { t } = React.useContext(LocalizationContext);
return ( <Stack.Navigator> <Stack.Screen name="Home" component={MyScreen} options={{ title: t('foo') }} /> </Stack.Navigator> );}
Refer to themes and the React documentation on context for help.