<html>
<head>
<style>
.scrollable-menu {
max-height : 200px;
overflow-y : auto;
}
</style>
<link rel="stylesheet" href="bootstrap/css/bootstrap.css" type="text/css"/>
<link rel="stylesheet" href="bootstrap/css/bootstrap-responsive.css" type="text/css"/>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script src="bootstrap/js/bootstrap.js"></script>
</head>
<body>
<div class="dropdown">
<a href="#" data-toggle="dropdown" class="dropdown-toggle">Program <b class="caret"></b></a>
<ul class="dropdown-menu scrollable-menu" >
<li class="dropdown-submenu">
<a tabindex="-1" href="#">Reach</a>
<ul class="dropdown-menu">
<li><a tabindex="-1" href="#">Level1</a></li>
<li><a tabindex="-1" href="#">Level2</a></li>
<li><a tabindex="-1" href="#">Level3</a></li>
<li><a tabindex="-1" href="#">Level4</a></li>
<li><a tabindex="-1" href="#">Level5</a></li>
<li><a tabindex="-1" href="#">Level6</a></li>
<li><a tabindex="-1" href="#">Level7</a></li>
</ul>
</li>
<li class="dropdown-submenu">
<a tabindex="-1" href="#">Reach For Reading</a>
<ul class="dropdown-menu">
<li><a tabindex="-1" href="#">Level1</a></li>
<li><a tabindex="-1" href="#">Level2</a></li>
<li><a tabindex="-1" href="#">Level3</a></li>
<li><a tabindex="-1" href="#">Level4</a></li>
<li><a tabindex="-1" href="#">Level5</a></li>
<li><a tabindex="-1" href="#">Level6</a></li>
<li><a tabindex="-1" href="#">Level7</a></li>
</ul>
</li>
<li class="dropdown-submenu">
<a tabindex="-1" href="#">Science</a>
<ul class="dropdown-menu">
<li><a tabindex="-1" href="#">Level1</a></li>
<li><a tabindex="-1" href="#">Level2</a></li>
<li><a tabindex="-1" href="#">Level3</a></li>
<li><a tabindex="-1" href="#">Level4</a></li>
<li><a tabindex="-1" href="#">Level5</a></li>
<li><a tabindex="-1" href="#">Level6</a></li>
<li><a tabindex="-1" href="#">Level7</a></li>
</ul>
</li>
<li class="dropdown-submenu">
<a tabindex="-1" href="#">World Culture and Geography</a>
<ul class="dropdown-menu">
<li><a tabindex="-1" href="#">Level1</a></li>
<li><a tabindex="-1" href="#">Level2</a></li>
<li><a tabindex="-1" href="#">Level3</a></li>
<li><a tabindex="-1" href="#">Level4</a></li>
<li><a tabindex="-1" href="#">Level5</a></li>
<li><a tabindex="-1" href="#">Level6</a></li>
<li><a tabindex="-1" href="#">Level7</a></li>
</ul>
</li>
<li class="dropdown-submenu">
<a tabindex="-1" href="#">Test</a>
<ul class="dropdown-menu">
<li><a tabindex="-1" href="#">Level1</a></li>
<li><a tabindex="-1" href="#">Level2</a></li>
<li><a tabindex="-1" href="#">Level3</a></li>
<li><a tabindex="-1" href="#">Level4</a></li>
<li><a tabindex="-1" href="#">Level5</a></li>
<li><a tabindex="-1" href="#">Level6</a></li>
<li><a tabindex="-1" href="#">Level7</a></li>
</ul>
</li>
<li class="dropdown-submenu">
<a tabindex="-1" href="#">Inside</a>
<ul class="dropdown-menu">
<li><a tabindex="-1" href="#">Level1</a></li>
<li><a tabindex="-1" href="#">Level2</a></li>
<li><a tabindex="-1" href="#">Level3</a></li>
<li><a tabindex="-1" href="#">Level4</a></li>
<li><a tabindex="-1" href="#">Level5</a></li>
<li><a tabindex="-1" href="#">Level6</a></li>
<li><a tabindex="-1" href="#">Level7</a></li>
</ul>
</li>
<li class="dropdown-submenu">
<a tabindex="-1" href="#">Edge</a>
<ul class="dropdown-menu">
<li><a tabindex="-1" href="#">Level1</a></li>
<li><a tabindex="-1" href="#">Level2</a></li>
<li><a tabindex="-1" href="#">Level3</a></li>
<li><a tabindex="-1" href="#">Level4</a></li>
<li><a tabindex="-1" href="#">Level5</a></li>
<li><a tabindex="-1" href="#">Level6</a></li>
<li><a tabindex="-1" href="#">Level7</a></li>
</ul>
</li>
<li class="dropdown-submenu">
<a tabindex="-1" href="#">Our World</a>
<ul class="dropdown-menu">
<li><a tabindex="-1" href="#">Level1</a></li>
<li><a tabindex="-1" href="#">Level2</a></li>
<li><a tabindex="-1" href="#">Level3</a></li>
<li><a tabindex="-1" href="#">Level4</a></li>
<li><a tabindex="-1" href="#">Level5</a></li>
<li><a tabindex="-1" href="#">Level6</a></li>
<li><a tabindex="-1" href="#">Level7</a></li>
</ul>
</li>
</ul>
</div>
</body>
我正在制作带有bootstrap的下拉菜单。当下拉菜单的高度高于屏幕尺寸时，我试图向其添加滚动条。正确添加滚动条但问题是现在子菜单未显示。他们是隐藏的。