html - 位置粘附子菜单不滚动

Question

我正在使用 bootstrap v-4 beta2，我想创建带有子菜单的粘性顶部菜单。一切都在桌面上工作，但在移动设备上，当我单击打开子菜单时，我看不到整个子菜单，当我滚动整个网站而不是菜单时。我发现我必须对 li.dropdown 做些什么——当我添加绝对位置时，它变得有点乱，但我看到了菜单。但是我不能得到我应该做的。这是代码:

li.dropdown:hover>.dropdown-menu {
  display: block;
}

li.dropdown {
  position: static;
}

.multi-columns {
  width: 100%;
}

<div class="nav-wrapper sticky-top">
  <div class="container">
    <nav class="navbar navbar-expand-lg navbar-light text-uppercase">
      <a class="navbar-brand" href="/"></a>
      <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
          </button>
      <div class="collapse navbar-collapse" id="navbarNav">
        <ul class="navbar-nav mr-auto">
          <li class="nav-item">
            <a class="nav-link" href="index.html">Domov <span class="sr-only">(current)</span></a>
          </li>
          <li class="nav-item">
            <a class="nav-link" href="blog.html">Blog</a>
          </li>
          <li class="nav-item active">
            <a class="nav-link" href="eshop.html">E-shop</a>
          </li>
          <li class="nav-item dropdown">
            <a class="nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button" aria-haspopup="true" aria-expanded="false">Dropdown</a>
            <div class="dropdown-menu multi-columns">
              <div class="row">
                <div class="col-md-3">
                  <h3 class="h5">Blog</h3>
                  <a class="dropdown-item" href="#">Action</a>
                  <a class="dropdown-item" href="#">Another action</a>
                  <a class="dropdown-item" href="#">Something else here</a>
                </div>
                <div class="col-md-3">
                  <h3 class="h5">Blog 2</h3>
                  <a class="dropdown-item" href="#">Action</a>
                  <a class="dropdown-item" href="#">Another action</a>
                  <a class="dropdown-item" href="#">Something else here</a>
                </div>
                <div class="col-md-3">
                  <h3 class="h5">Blog 3</h3>
                  <a class="dropdown-item" href="#">Action</a>
                  <a class="dropdown-item" href="#">Another action</a>
                  <a class="dropdown-item" href="#">Something else here</a>
                </div>
                <div class="col-md-3">
                  <h3 class="h5">Blog 4</h3>
                  <a class="dropdown-item" href="#">Action</a>
                  <a class="dropdown-item" href="#">Another action</a>
                  <a class="dropdown-item" href="#">Something else here</a>
                </div>
              </div>
            </div>
          </li>
        </ul>
        <form action="" class="form-inline">
          <select class="select2 form-control" style="width: 100%;">
    
              </select>
        </form>
      </div>
    </nav>
    <!-- /.nav -->
  </div>
  <!-- /.container -->
</div>
<!-- /.nav-wrapper -->

此外，在桌面上，当我将鼠标悬停在“下拉菜单”上时，它会显示出来，但当我将鼠标放在子菜单上时，它会消失。我应该移动带有 margin-top: -10px 或 smh 的子菜单吗？或者有什么解决办法吗？

编辑

最主要的是子菜单大于视口(viewport)，然后我根本无法在上面滚动

Answer 1

如果您需要子菜单在内容中滚动，为此您需要指定max-height 和overflow: scroll;。

您还需要在 dropdown-menu 多列 分区内将 col-md-3 更改为 col-lg-3。

CSS

@media (max-width: 991px){
.multi-columns{
  max-height: 300px;
  overflow: auto;
     }
  }

演示片段:

li.dropdown:hover>.dropdown-menu {
  display: block;
}

li.dropdown {
  position: static;
}

.multi-columns {
  width: 100%;
}
@media (max-width: 991px){
.multi-columns{
  max-height: 300px;
  overflow: auto;
     }
  }

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.3/umd/popper.min.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-beta/css/bootstrap.min.css" rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-beta/js/bootstrap.min.js"></script>


<div class="nav-wrapper sticky-top">
  <div class="container">
    <nav class="navbar navbar-expand-lg navbar-light text-uppercase">
      <a class="navbar-brand" href="/"></a>
      <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
          </button>
      <div class="collapse navbar-collapse" id="navbarNav">
        <ul class="navbar-nav mr-auto">
          <li class="nav-item">
            <a class="nav-link" href="index.html">Domov <span class="sr-only">(current)</span></a>
          </li>
          <li class="nav-item">
            <a class="nav-link" href="blog.html">Blog</a>
          </li>
          <li class="nav-item active">
            <a class="nav-link" href="eshop.html">E-shop</a>
          </li>
          <li class="nav-item dropdown">
            <a class="nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button" aria-haspopup="true" aria-expanded="false">Dropdown</a>
            <div class="dropdown-menu multi-columns">
              <div class="row">
                <div class="col-lg-3">
                  <h3 class="h5">Blog</h3>
                  <a class="dropdown-item" href="#">Action</a>
                  <a class="dropdown-item" href="#">Another action</a>
                  <a class="dropdown-item" href="#">Something else here</a>
                </div>
                <div class="col-lg-3">
                  <h3 class="h5">Blog 2</h3>
                  <a class="dropdown-item" href="#">Action</a>
                  <a class="dropdown-item" href="#">Another action</a>
                  <a class="dropdown-item" href="#">Something else here</a>
                </div>
                <div class="col-lg-3">
                  <h3 class="h5">Blog 3</h3>
                  <a class="dropdown-item" href="#">Action</a>
                  <a class="dropdown-item" href="#">Another action</a>
                  <a class="dropdown-item" href="#">Something else here</a>
                </div>
                <div class="col-lg-3">
                  <h3 class="h5">Blog 4</h3>
                  <a class="dropdown-item" href="#">Action</a>
                  <a class="dropdown-item" href="#">Another action</a>
                  <a class="dropdown-item" href="#">Something else here</a>
                </div>
              </div>
            </div>
          </li>
        </ul>
        <form action="" class="form-inline">
          <select class="select2 form-control" style="width: 100%;">
    
              </select>
        </form>
      </div>
    </nav>
    <!-- /.nav -->
  </div>
  <!-- /.container -->
</div>
<!-- /.nav-wrapper -->

希望对您有所帮助。 Codepen demo link.谢谢。