locale-android.java

static String currentLocale;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    MainActivity.currentLocale = getResources().getConfiguration().locale.toString();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);

    String locale = newConfig.locale.toString();
    if (!MainActivity.currentLocale.equals(locale)) {
        MainActivity.currentLocale = locale;
        final ReactInstanceManager instanceManager = getReactInstanceManager();
        instanceManager.recreateReactContextInBackground();
    }
}