Yii2 bootstrap下拉问题

Question

我正在尝试将yii下拉窗口小部件放入我的应用程序中。我这样做的方式是http://www.yiiframework.com/doc-2.0/yii-bootstrap-dropdown.html。

use yii/bootstrap/Dropdown;
...

<ul>
...
<li class="dropdown">
    <a href="#" data-toggle="dropdown" class="dropdown-toggle">Label <b class="caret"></b></a>                     
    <?php
        echo Dropdown::widget([
            'items'  => [
                 ['label' => 'DropdownA', 'url' => '#'],
                 ['label' => 'DropdownB', 'url' => '#'],
              ],
        ]);
    ?>
</li> 
...
</ul>

但链接不会扩展。请告诉我我的错误。

这些是AppAssets：

public $css = [
    //'css/site.css',S
    'newtemp/styles/style.css',
    'newtemp/styles/animate.css',
    'newtemp/styles/font-awesome.css',
    'newtemp/styles/font-awesome2.css',
    'newtemp/styles/framework.css',
    'newtemp/styles/owl.theme.css',
    'newtemp/styles/swipebox.css',
    'newtemp/styles/bootstrap.css',


];
public $js = [

    'newtemp/scripts/jqueryui.js',
    'newtemp/scripts/contact.js',
    'newtemp/scripts/framework.js',
    'newtemp/scripts/framework.launcher.js',
    'newtemp/scripts/framework.plugins.js',
    'newtemp/scripts/custom.js',

非常感谢。