使用CSS时，Dropmenu不起作用

Question

我有一个CSS文件，我必须在我的dropmenu上使用它。问题是菜单不起作用：我无法看到主标题下面的列表。在此示例中，列表应位于My Home，[username]。

之下

您可以在下面找到CSS文件的相关部分。

PHP：

<nav class="navbar navbar-inverse navbar-fixed-top" role="navigation">
    <div class="container">
        <!-- Brand and toggle get grouped for better mobile display -->
        <div class="navbar-header">
            <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1">
                <span class="sr-only">Toggle navigation</span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
            </button>



            <li>
            <a class="navbar-brand" href="home.php">My Home, <?php echo $_SESSION["username"]; ?> &#9662; </a> 
                <ul>
                  <div class="dropdown">
                    <div class="dropdown-menu">
                    <li><a href="">Item1</a></li>
                    <li><a href="">Item2</a></li>
                    <li><a href="">Item3</a></li>
                    <li><a href="">Item4</a></li>
                 </div>
                </ul>
            </li>


        </div>
        <!-- Collect the nav links, forms, and other content for toggling -->
        <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
            <ul class="nav navbar-nav">
                <li>
                    <a href="">Event</a>
                </li>
                <li>
                    <a href="">Event</a>
                </li>
                <li>
                    <a href="">Event</a>
                </li>
                <li>
                    <a href='logout.php'>Logout</a>
                </li>
            </ul>

        </div>
        <!-- /.navbar-collapse -->
    </div>
    <!-- /.container -->
</nav>

CSS

.caret {
  display: inline-block;
  width: 0;
  height: 0;
  margin-left: 2px;
  vertical-align: middle;
  border-top: 4px dashed;
  border-top: 4px solid \9;
  border-right: 4px solid transparent;
  border-left: 4px solid transparent;
}
.dropup,
.dropdown {
  position: relative;
}
.dropdown-toggle:focus {
  outline: 0;
}
.dropdown-menu {
  position: absolute;
  top: 100%;
  left: 0;
  z-index: 1000;
  display: none;
  float: left;
  min-width: 160px;
  padding: 5px 0;
  margin: 2px 0 0;
  font-size: 14px;
  text-align: left;
  list-style: none;
  background-color: #fff;
  -webkit-background-clip: padding-box;
          background-clip: padding-box;
  border: 1px solid #ccc;
  border: 1px solid rgba(0, 0, 0, .15);
  border-radius: 4px;
  -webkit-box-shadow: 0 6px 12px rgba(0, 0, 0, .175);
          box-shadow: 0 6px 12px rgba(0, 0, 0, .175);
}
.dropdown-menu.pull-right {
  right: 0;
  left: auto;
}
.dropdown-menu .divider {
  height: 1px;
  margin: 9px 0;
  overflow: hidden;
  background-color: #e5e5e5;
}
.dropdown-menu > li > a {
  display: block;
  padding: 3px 20px;
  clear: both;
  font-weight: normal;
  line-height: 1.42857143;
  color: #333;
  white-space: nowrap;
}
.dropdown-menu > li > a:hover,
.dropdown-menu > li > a:focus {
  color: #262626;
  text-decoration: none;
  background-color: #f5f5f5;
}
.dropdown-menu > .active > a,
.dropdown-menu > .active > a:hover,
.dropdown-menu > .active > a:focus {
  color: #fff;
  text-decoration: none;
  background-color: #337ab7;
  outline: 0;
}
.dropdown-menu > .disabled > a,
.dropdown-menu > .disabled > a:hover,
.dropdown-menu > .disabled > a:focus {
  color: #777;
}
.dropdown-menu > .disabled > a:hover,
.dropdown-menu > .disabled > a:focus {
  text-decoration: none;
  cursor: not-allowed;
  background-color: transparent;
  background-image: none;
  filter: progid:DXImageTransform.Microsoft.gradient(enabled = false);
}
.open > .dropdown-menu {
  display: block;
}
.open > a {
  outline: 0;
}
.dropdown-menu-right {
  right: 0;
  left: auto;
}
.dropdown-menu-left {
  right: auto;
  left: 0;
}
.dropdown-header {
  display: block;
  padding: 3px 20px;
  font-size: 12px;
  line-height: 1.42857143;
  color: #777;
  white-space: nowrap;
}
.dropdown-backdrop {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 990;
}
.pull-right > .dropdown-menu {
  right: 0;
  left: auto;
}
.dropup .caret,
.navbar-fixed-bottom .dropdown .caret {
  content: "";
  border-top: 0;
  border-bottom: 4px dashed;
  border-bottom: 4px solid \9;
}
.dropup .dropdown-menu,
.navbar-fixed-bottom .dropdown .dropdown-menu {
  top: auto;
  bottom: 100%;
  margin-bottom: 2px;
}

Answer 1

您需要触发菜单才能显示的内容。在我的场景中，我实现了一个带有“dropdown”类的div，并将其格式化为以下

.dropup,
.dropdown {
  position: relative;
  border-style: solid;
  margin-top: 100;
}


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

.dropdown-toggle:focus {
  outline: 0;
}
.dropdown-menu {
  position: absolute;
  top: 20%;
  left: 0;
  z-index: 1000;
  display: none;
  float: left;
  min-width: 160px;
  padding: 5px 0;
  margin: 2px 0 0;
  font-size: 14px;
  text-align: left;
  list-style: none;
  background-color: #fff;
  -webkit-background-clip: padding-box;
          background-clip: padding-box;
  border: 1px solid #ccc;
  border: 1px solid rgba(0, 0, 0, .15);
  border-radius: 4px;
  -webkit-box-shadow: 0 6px 12px rgba(0, 0, 0, .175);
          box-shadow: 0 6px 12px rgba(0, 0, 0, .175);
}
.dropdown-menu.pull-right {
  right: 0;
  left: auto;
}
.dropdown-menu .divider {
  height: 1px;
  margin: 9px 0;
  overflow: hidden;
  background-color: #e5e5e5;
}
.dropdown-menu > li > a {
  display: block;
  padding: 3px 20px;
  clear: both;
  font-weight: normal;
  line-height: 1.42857143;
  color: #333;
  white-space: nowrap;
}
.dropdown-menu > li > a:hover,
.dropdown-menu > li > a:focus {
  color: #262626;
  text-decoration: none;
  background-color: #f5f5f5;
}
.dropdown-menu > .active > a,
.dropdown-menu > .active > a:hover,
.dropdown-menu > .active > a:focus {
  color: #fff;
  text-decoration: none;
  background-color: #337ab7;
  outline: 0;
}
.dropdown-menu > .disabled > a,
.dropdown-menu > .disabled > a:hover,
.dropdown-menu > .disabled > a:focus {
  color: #777;
}
.dropdown-menu > .disabled > a:hover,
.dropdown-menu > .disabled > a:focus {
  text-decoration: none;
  cursor: not-allowed;
  background-color: transparent;
  background-image: none;
  filter: progid:DXImageTransform.Microsoft.gradient(enabled = false);
}
.open > .dropdown-menu {
  display: block;
}
.open > a {
  outline: 0;
}
.dropdown-menu-right {
  right: 0;
  left: auto;
}
.dropdown-menu-left {
  right: auto;
  left: 0;
}
.dropdown-header {
  display: block;
  padding: 3px 20px;
  font-size: 12px;
  line-height: 1.42857143;
  color: #777;
  white-space: nowrap;
}
.dropdown-backdrop {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 990;
}
.pull-right > .dropdown-menu {
  right: 0;
  left: auto;
}
.dropup .caret,
.navbar-fixed-bottom .dropdown .caret {
  content: "";
  border-top: 0;
  border-bottom: 4px dashed;
  border-bottom: 4px solid \9;
}
.dropup .dropdown-menu,
.navbar-fixed-bottom .dropdown .dropdown-menu {
  top: auto;
  bottom: 100%;
  margin-bottom: 2px;
}

HTML看起来像这样：

<li>
            <a class="navbar-brand" href="#">My Home, <?php echo $_SESSION["username"]; ?> &#9662; </a>

                <ul>
                  <div class="dropdown">
                   <div class="dropdown-menu">
                    <li><a href="">Item1</a></li>
                    <li><a href="">Item2</a></li>
                    <li><a href="">Item3</a></li>
                    <li><a href="">Item4</a></li>
                 </div>                 
                </div>

                </ul>
            </li>

当您将鼠标悬停在“我的主页”按钮下方的黑框上时，您可以看到要退出的下拉菜单。在这里你有jsfiddle：https://jsfiddle.net/Lzcubffn/

当然，您需要在div中添加一些真实内容来触发菜单。我只是拿了div盒子的黑色边框。

我希望，我可以帮助你