protected function beforeRender($view)
    {
    if (!Yii::app()->detectMobileBrowser->showMobile) {
    Yii::app()->setTheme('mobile');
    $this->layout = $this->getLayoutFile('//layouts/column1');
    print_r($this->layout);
    $cs = Yii::app()->clientScript;
    $cs->registerCssFile( yii::app()->theme->baseurl. '/css/mobile.css' );
    //$this->layout ="//layouts/column1";
    }


**************column1.php*********** path (themes/mobile/layouts/column1) ********

<?php $this->beginContent('//layouts/main'); ?>
<div class="container">
<?php echo $content; ?>
</div>
<?php $this->endContent(); ?>