LocaleManager.java

/*
 * @author Rolf Smit
 * Copyright: © Rolf Smit / NeoTech Software
 */

package org.neotech.library.utilities;

import android.content.Context;
import android.content.res.Configuration;
import android.content.res.Resources;
import android.os.Build;

import androidx.annotation.NonNull;

import java.util.Locale;

import static android.os.Build.VERSION_CODES.N;

public class LocaleManager {

    /**
     * A LocaleProvider or locale String can often not be injected because injection almost
     * always happens after attachBaseContext. Therefore it could make sense to let the Application
     * class inherit from LocaleProvider so that everywhere where you have access to a Context
     * object you can also get the LocaleProvider. This method does exactly that, it gets the
     * Application Context then casts that to a LocaleProvider to get the desired locale from.
     */
    public static Context setLocale(@NonNull Context context) {
        return setLocale(context, ((LocaleProvider) context.getApplicationContext()));
    }

    public static Context setLocale(@NonNull Context context, @NonNull LocaleProvider localeProvider) {
        return setLocale(context, localeProvider.getDesiredLanguageCode());
    }

    /**
     * Call this method in:
     * - Application.attachBaseContext(setLocale(...))
     * - Application.onConfigurationChanged() { setLocale(...) }
     * - Activity.attachBaseContext(setLocale(...))
     *
     * @param context  current Context.
     * @param language the desired language
     * @return Context with updated configuration.
     */
    public static Context setLocale(@NonNull Context context, @NonNull String language) {
        return updateResources(context, language);
    }

    private static Context updateResources(@NonNull Context context, @NonNull String language) {
        final Locale newLocale = new Locale(language);

        final Resources resources = context.getResources();
        if (getLocale(context).getLanguage().equals(newLocale.getLanguage())) {
            return context;
        }
        Locale.setDefault(newLocale);

        final Configuration config = new Configuration(resources.getConfiguration());
        config.setLocale(newLocale);
        context = context.createConfigurationContext(config);
        return context;
    }

    @NonNull
    public static Locale getLocale(Context context) {
        Configuration config = context.getResources().getConfiguration();
        return Build.VERSION.SDK_INT >= N ? config.getLocales().get(0) : config.locale;
    }

    public interface LocaleProvider {
        String getDesiredLanguageCode();
    }
}