Change Android application locale

AppLocaleManager.java

package org.kman.Compat.util;

import java.util.Locale;

import android.annotation.TargetApi;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.res.Configuration;
import android.content.res.Resources;
import android.os.Build;
import android.preference.PreferenceManager;
import android.text.TextUtils;

public class AppLocaleManager {
	private static final String TAG = "AppLocaleManager";

	// Has to match preference key in the .xml file
	private static final String PREFS_KEY = "prefsUILocale";

	public static AppLocaleManager factory() {
		return gInstance;
	}

	public void applyFromPrefs(Context context) {
		final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
		final String newLocaleCode = prefs.getString(PREFS_KEY, null);
		applyImpl(context, newLocaleCode);
	}

	public void applyFromPrefs(Context context, SharedPreferences prefs) {
		final String newLocaleCode = prefs.getString(PREFS_KEY, null);
		applyImpl(context, newLocaleCode);
	}

	public void applyFromValue(Context context, String newLocaleCode) {
		applyImpl(context, newLocaleCode);
	}

	public Locale getSystemLocale() {
		if (gSavedSystemLocale != null) {
			return gSavedSystemLocale;
		}
		return Locale.getDefault();
	}

	private void applyImpl(Context context, String newLocaleCode) {
		applyImplToContext(context, newLocaleCode);

		final Context app = context.getApplicationContext();
		if (app != context) {
			applyImplToContext(app, newLocaleCode);
		}
	}

	private boolean applyImplToContext(Context context, String newLocaleCode) {
		MyLog.i(TAG, "applyImpl: newLocaleCode = %s, savedSystemLocale = %s", newLocaleCode, gSavedSystemLocale);

		Locale newLocale = null;
		if (TextUtils.isEmpty(newLocaleCode)) {
			// System locale
			if (gSavedSystemLocale == null) {
				// We've never changed it
				return true;
			}
			newLocale = gSavedSystemLocale;
		} else {
			// Non-system, explicit locale
			if (gSavedSystemLocale == null) {
				gSavedSystemLocale = Locale.getDefault();
			}

			try {
				final String[] split = newLocaleCode.split("_");
				if (split != null && split.length >= 2) {
					newLocale = new Locale(split[0], split[1]);
				} else {
					newLocale = new Locale(newLocaleCode);
				}
			} catch (Exception x) {
				// Just in case
				MyLog.w(TAG, x);
				newLocale = null;
			}
		}

		MyLog.i(TAG, "applyImpl: newLocale = %s", newLocale);

		if (newLocale == null) {
			return false;
		}

		try {
			final Resources resources = context.getResources();
			if (resources == null) {
				return false;
			}
			final Configuration config = resources.getConfiguration();
			if (config == null) {
				return false;
			}

			if (config.locale == null || !localesEqual(config.locale, newLocale)) {
				config.locale = newLocale;
				final ConfigCompat configCompat = ConfigCompat.factory();
				configCompat.setLayoutDirection(config, newLocale);
				resources.updateConfiguration(config, resources.getDisplayMetrics());
			}

			final Locale defaultLocale = Locale.getDefault();
			if (defaultLocale == null || !localesEqual(defaultLocale, newLocale)) {
				Locale.setDefault(newLocale);
			}
		} catch (Exception x) {
			// Just in case
			MyLog.w(TAG, x);
		}
		return true;
	}

	private AppLocaleManager() {
	}

	private static class ConfigCompat {
		static ConfigCompat factory() {
			if (Build.VERSION.SDK_INT >= 17) {
				return new ConfigCompat_api17();
			}
			return new ConfigCompat();
		}

		void setLayoutDirection(Configuration config, Locale locale) {
		}
	}

	private boolean localesEqual(Locale a, Locale b) {
		final String langA = a.getLanguage();
		final String countryA = a.getCountry();

		final String langB = b.getLanguage();
		final String countryB = b.getCountry();

		return ((langA == null && langB == null) || langA.equals(langB))
				&& ((countryA == null && countryB == null) || countryA.equals(countryB));

	}

	@TargetApi(17)
	private static class ConfigCompat_api17 extends ConfigCompat {
		@Override
		void setLayoutDirection(Configuration config, Locale locale) {
			config.setLayoutDirection(locale);
		}
	}

	private static Locale gSavedSystemLocale;
	private static AppLocaleManager gInstance = new AppLocaleManager();
}