想去掉layout , 使用 $this->layout = false 之後，頁面上通過CommonAsset::register($this)引入的Js、Css都沒有了，解決方法如下：
<?php
use backend\assets\CommonAsset;
CommonAsset::register($this);
?>
<?php $this->beginPage()?>//必需
<!DOCTYPE html>
<html lang="UTF-8">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1, user-scalable=no" />
<title></title>
<?php $this->head() ?>//必需
<meta name="author" content="">
</head>
<body>
<?php $this->beginBody() ?>//必需
<div class="container">
</div>
<?php $this->endBody() ?>//必需
</body>
</html>
<?php $this->endPage() ?>//必需