src/Controller/AppController.php
protected function _setTheme()
    {
        $theme = $this->request->getParam('theme');
        if ($theme) {
            $this->viewBuilder()->setTheme($theme);
        }
    }
protected function _setTheme()
    {
        $theme = $this->request->getParam('theme');
        if ($theme) {
            $this->viewBuilder()->setTheme($theme);
        }
    }
protected function _setTheme ( ) { $ theme = $ this -> request -> getParam ( 'theme' ) ; if ( $ theme ) { $ this -> viewBuilder ( ) -> setTheme ( $ theme ) ; } }
Setup application theme.

@return  void
Setup application theme .