Prestashop 1.6覆盖类在移动设备中不起作用

I have module that overrides the classes/Tools.php class. It works fine in desktop computers, but in mobile devices it's not working.

This is my override, located in: mymodule/overrides/classes/Tools.php:

<?php
class Tools extends ToolsCore
{
        public static function setCurrency($cookie)
        {
                // This is not working BTW
                $logger = new FileLogger(0);
                $logger->setFilename(_PS_ROOT_DIR_ . '/log/debug.log');
                $logger->logDebug("HOLA MUNDO");

                if (!Module::isEnabled('mymodule'))
                        return parent::setCurrency($cookie);

                if (Tools::isSubmit('SubmitCurrency'))
                        return parent::setCurrency($cookie);

                if ((int)$cookie->id_currency)
                        return parent::setCurrency($cookie);

                $cookie->id_currency = (int)Configuration::get('FO_DEFAULT_CURRENCY');
                return parent::setCurrency($cookie);
        }
}

Why is this not working in mobile device?!