Android: How to get string in specific locale WITHOUT changing the current locale

You can use this for API +17

@NonNull
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
public static String getStringByLocal(Activity context, int id, String locale) {
    Configuration configuration = new Configuration(context.getResources().getConfiguration());
    configuration.setLocale(new Locale(locale));
    return context.createConfigurationContext(configuration).getResources().getString(id);
}

Update (1) : How to support old versions.

@NonNull
public static String getStringByLocal(Activity context, int resId, String locale) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1)
        return getStringByLocalPlus17(context, resId, locale);
    else
        return getStringByLocalBefore17(context, resId, locale);
}

@NonNull
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
private static String getStringByLocalPlus17(Activity context, int resId, String locale) {
    Configuration configuration = new Configuration(context.getResources().getConfiguration());
    configuration.setLocale(new Locale(locale));
    return context.createConfigurationContext(configuration).getResources().getString(resId);
}

private static String getStringByLocalBefore17(Context context,int resId, String language) {
    Resources currentResources = context.getResources();
    AssetManager assets = currentResources.getAssets();
    DisplayMetrics metrics = currentResources.getDisplayMetrics();
    Configuration config = new Configuration(currentResources.getConfiguration());
    Locale locale = new Locale(language);
    Locale.setDefault(locale);
    config.locale = locale;
/*
 * Note: This (temporarily) changes the devices locale! TODO find a
 * better way to get the string in the specific locale
 */
    Resources defaultLocaleResources = new Resources(assets, metrics, config);
    String string = defaultLocaleResources.getString(resId);
    // Restore device-specific locale
    new Resources(assets, metrics, currentResources.getConfiguration());
    return string;
}

Update (2): Check this article

You can save all the strings of the default locale in a Map inside a global class, like Application that is executed when launching the app:

public class DualLocaleApplication extends Application {

    private static Map<Integer, String> defaultLocaleString;

    public void onCreate() {
        super.onCreate();
        Resources currentResources = getResources();
        AssetManager assets = currentResources.getAssets();
        DisplayMetrics metrics = currentResources.getDisplayMetrics();
        Configuration config = new Configuration(
                currentResources.getConfiguration());
        config.locale = Locale.ENGLISH;
        new Resources(assets, metrics, config);
        defaultLocaleString = new HashMap<Integer, String>();
        Class<?> stringResources = R.string.class;
        for (Field field : stringResources.getFields()) {
            String packageName = getPackageName();
            int resId = getResources().getIdentifier(field.getName(), "string", packageName);
            defaultLocaleString.put(resId, getString(resId));
        }
        // Restore device-specific locale
        new Resources(assets, metrics, currentResources.getConfiguration());
    }

    public static String getStringInDefaultLocale(int resId) {
        return defaultLocaleString.get(resId);
    }

}

This solution is not optimal, but you won't have concurrency problems.

Thanks to @Khaled Lela answer, I've made a Kotlin extension:

fun Context.getStringByLocale(@StringRes stringRes: Int, locale: Locale, vararg formatArgs: Any): String {
    val configuration = Configuration(resources.configuration)
    configuration.setLocale(locale)
    return createConfigurationContext(configuration).resources.getString(stringRes, *formatArgs)
}

And I'm using directly within an Activity, Fragment or Context related classes, just simply calling:

getStringByLocale(R.string.my_text, Locale.UK) or with arguments:

getStringByLocale(R.string.my_other_text, Locale.RU, arg1, arg2, arg3)