使子菜单项显示在位于绝对位置的div上

Question

我正在尝试使用CSS创建垂直菜单。当我将鼠标悬停在子菜单项上时，其中一半的子菜单不会显示。请参阅下图：

可能会发生这种情况，因为蓝色背景中的div和包含菜单的div都位于绝对位置。您可以在此处查看代码：https://jsfiddle.net/02vc01cw/2/

您能否告诉我如何使子菜单正常显示？ 提前谢谢。

这是我的代码：

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#bg {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: 0;
    overflow: hidden;
    background-color: #437DCC;
}
#drawer {
    z-index: 2;   
    overflow: hidden;
    height: 100%;
    width: 270px !important;
    position: absolute;
    overflow: hidden;
}
#gnavi-links > ul {
    list-style-type: none;
    background: #fff;
}
#gnavi-links > ul > li {
    margin-bottom: 10px;
}
#gnavi-links > ul > li > a {
    display: block;
    height: 40px;
    line-height: 40px;
    color: #1a1a1a;
    font-family: 'Calibre-Bold', sans-serif;
    font-weight: bold;
    letter-spacing: 0.25em;
    text-transform: uppercase;
}
#gnavi-links > ul > li > ul {
    list-style-type: none;
    margin-left: -50px;
    margin-right: 5px;
}
#gnavi-links > ul > li> ul > li > a {
    font-size: 13px;
    display: block;
    padding: 5px 16px;
    color: #1a1a1a;
    text-decoration: none;
    letter-spacing: 0.20em;
    text-transform: uppercase;
}
#gnavi-links > ul > li> a:hover {
    color: #19a69a;
}
#gnavi-links > ul > li> ul > li a:hover {
    background-color: #5A5959;
    color: #fff;
}
#gnavi-links > ul > li> ul > li ul {
    display: none;
}
#gnavi-links > ul > li> ul > li:hover ul {
    position: absolute;
    display: block;
    background: #999;
    margin-left: 170px;
    margin-top: -25px;    
}
#gnavi-links > ul > li> ul > li > ul > li {
    width: 150px;
}

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<div id="drawer">
   <nav class="drawer-nav" id="gnavi-links" role="navigation">
      <ul>
         <li><a>Menu Item</a></li>
         <li>
            <a>Menu Item</a>
            <ul>
               <li><a>Sub Menu Test 1</a></li>
               <li>
                  <a>Sub Menu Test 2</a>
                  <ul>
                     <li><a>Sub Menu Test 1</a></li>
                     <li><a>Sub Menu Test 2</a></li>
                     <li><a>Sub Menu Test 3</a></li>
                  </ul>
               </li>
               <li><a>Sub Menu Test 3</a></li>
            </ul>
         </li>
         <li><a>Menu Item</a></li>
      </ul>
   </nav>
</div>
<div id="bg">
</div>

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Answer 1

删除overflow: hidden

上的#drawer

#drawer {
    z-index: 2;   
    height: 100%;
    width: 270px !important;
    position: absolute;
}

Demo

Answer 2

这是因为你的代码中有overflow:hidden，删除它并且它会起作用：

#bg {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: -1;
    background-color: #437DCC;
}
#drawer {
    z-index: 2;   
    height: 100%;
    width: 270px !important;
    position: absolute;
}
#gnavi-links > ul {
    list-style-type: none;
    background: #fff;
}
#gnavi-links > ul > li {
    margin-bottom: 10px;
}
#gnavi-links > ul > li > a {
    display: block;
    height: 40px;
    line-height: 40px;
    color: #1a1a1a;
    font-family: 'Calibre-Bold', sans-serif;
    font-weight: bold;
    letter-spacing: 0.25em;
    text-transform: uppercase;
}
#gnavi-links > ul > li > ul {
    list-style-type: none;
    margin-left: -50px;
    margin-right: 5px;
}
#gnavi-links > ul > li> ul > li > a {
    font-size: 13px;
    display: block;
    padding: 5px 16px;
    color: #1a1a1a;
    text-decoration: none;
    letter-spacing: 0.20em;
    text-transform: uppercase;
}
#gnavi-links > ul > li> a:hover {
    color: #19a69a;
}
#gnavi-links > ul > li> ul > li a:hover {
    background-color: #5A5959;
    color: #fff;
}
#gnavi-links > ul > li> ul > li ul {
    display: none;
}
#gnavi-links > ul > li> ul > li:hover ul {
    position: absolute;
    display: block;
    background: #999;
    margin-left: 170px;
    margin-top: -25px;    
}
#gnavi-links > ul > li> ul > li > ul > li {
    width: 150px;
}

<div id="drawer">
   <nav class="drawer-nav" id="gnavi-links" role="navigation">
      <ul>
         <li><a>Menu Item</a></li>
         <li>
            <a>Menu Item</a>
            <ul>
               <li><a>Sub Menu Test 1</a></li>
               <li>
                  <a>Sub Menu Test 2</a>
                  <ul>
                     <li><a>Sub Menu Test 1</a></li>
                     <li><a>Sub Menu Test 2</a></li>
                     <li><a>Sub Menu Test 3</a></li>
                  </ul>
               </li>
               <li><a>Sub Menu Test 3</a></li>
            </ul>
         </li>
         <li><a>Menu Item</a></li>
      </ul>
   </nav>
</div>
<div id="bg">
</div>