下面的div上的bootstrap 4下拉菜单

Question

我试图让bootstrap 4响应式顶级导航出现在我的容器div上，但没有运气，我似乎无法找到解决方案。

这是顶级导航仪的工作原理
W3Schools编辑器

这是我的代码的jsfiddle
的jsfiddle

 function myFunction() { var x = document.getElementById("myTopnav"); if (x.className === "topnav") { x.className += " responsive"; } else { x.className = "topnav"; } } 

  /* Add a black background color to the top navigation */ .topnav { background-color: #333; overflow: hidden; } /* Style the links inside the navigation bar */ .topnav a { float: left; display: block; color: #f2f2f2; text-align: center; padding: 14px 16px; text-decoration: none; font-size: 17px; } /* Add an active class to highlight the current page */ .active { background-color: #4CAF50; color: white; } /* Hide the link that should open and close the topnav on small screens */ .topnav .icon { display: none; } /* Dropdown container - needed to position the dropdown content */ .dropdown { float: left; overflow: visible; } /* Style the dropdown button to fit inside the topnav */ .dropdown .dropbtn { font-size: 17px; border: none; outline: none; color: white; padding: 14px 16px; background-color: inherit; font-family: inherit; margin: 0; } /* Style the dropdown content (hidden by default) */ .dropdown-content { display: none; position: relative; background-color: #f9f9f9; min-width: 160px; box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2); z-index: 2; } /* Style the links inside the dropdown */ .dropdown-content a { float: none; color: black; padding: 12px 16px; text-decoration: none; display: block; text-align: left; } /* Add a dark background on topnav links and the dropdown button on hover */ .topnav a:hover, .dropdown:hover .dropbtn { background-color: #555; color: white; } /* Add a grey background to dropdown links on hover */ .dropdown-content a:hover { background-color: #ddd; color: black; } /* Show the dropdown menu when the user moves the mouse over the dropdown button */ .dropdown:hover .dropdown-content { display: block; } /* When the screen is less than 600 pixels wide, hide all links, except for the first one ("Home"). Show the link that contains should open and close the topnav (.icon) */ @media screen and (max-width: 600px) { .topnav a:not(:first-child), .dropdown .dropbtn { display: none; } .topnav a.icon { float: right; display: block; } } /* The "responsive" class is added to the topnav with JavaScript when the user clicks on the icon. This class makes the topnav look good on small screens (display the links vertically instead of horizontally) */ @media screen and (max-width: 600px) { .topnav.responsive { position: relative; } .topnav.responsive a.icon { position: absolute; right: 0; top: 0; } .topnav.responsive a { float: none; display: block; text-align: left; } .topnav.responsive .dropdown { float: none; } .topnav.responsive .dropdown-content { position: relative; } .topnav.responsive .dropdown .dropbtn { display: block; width: 100%; text-align: left; } } 

 <button class="dropbtn">Equipment <i class="fa fa-caret-down"></i> </button> <div class="dropdown-content"> <a href="equip.php">Manage equipment</a> <a href="add_equip.php">Add equipment</a> </div> </div> <div class="dropdown"> <button class="dropbtn">Stock <i class="fa fa-caret-down"></i> </button> <div class="dropdown-content"> <a href="Stock.php">Manage stock</a> <a href="add_stock.php">Add stock</a> </div> </div> <div class="dropdown"> <button class="dropbtn">Reports <i class="fa fa-caret-down"></i> </button> <div class="dropdown-content"> <a href="#">Report 1 </a> <a href="#">Report 1 </a> <a href="#">Report 1 </a> </div> </div> <a href="javascript:void(0);" class="icon" onclick="myFunction()">&#9776;</a> </div> <div class="container-fluid"> <div class="row"> <div class="col-md-6"> <?php echo display_msg($msg); ?> </div> </div> <div class="row"> <div class="col-md-3"> <div class="panel panel-box clearfix"> <div class="panel-icon bg-green"> <i class="glyphicon glyphicon-user"></i> </div> <div class="panel-value pull-right"> <h2 class="margin-top"> <?php echo $c_contractors['total']; ?> </h2> <p class="text-muted">Contractors</p> </div> </div> </div> <div class="col-md-3"> <div class="panel panel-box clearfix"> <div class="panel-icon pull-left bg-red"> <i class="glyphicon glyphicon-list"></i> </div> <div class="panel-value pull-right"> <h2 class="margin-top"> <?php echo $c_jobs_active['total']; ?> </h2> <p class="text-muted">Active Jobs</p> </div> </div> </div> <div class="col-md-3"> <div class="panel panel-box clearfix"> <div class="panel-icon pull-left bg-blue"> <i class="glyphicon glyphicon-list"></i> </div> <div class="panel-value pull-right"> <h2 class="margin-top"> <?php echo $c_jobs_pending['total']; ?> </h2> <p class="text-muted">Pending jobs</p> </div> </div> </div> <div class="col-md-3"> <div class="panel panel-box clearfix"> <div class="panel-icon pull-left bg-yellow"> <i class="glyphicon glyphicon-list"></i> </div> <div class="panel-value pull-right"> <h2 class="margin-top"> <?php echo $c_jobs_completed['total']; ?> </h2> <p class="text-muted">Completed Jobs YTD</p> </div> </div> </div> </div> <div class="row"> <div class="col-md-12"> <div class="panel"> <div class="jumbotron text-center"> <h1>Any problems let me know.</h1> </div> </div> </div> </div> </div> 

我敢肯定，我已经看过了一些简单的事情
干杯，

Answer 1

首先，将.topnav类更改为：

.topnav {
    float:left;
    width:100%;
    position:relative;
    background-color: #333;
}

然后从.dropdown类中消除溢出。 最后，在.dropdown-content类中更改position：相对于position：absolute。

不要忘了添加一个明确的名称：两种样式都在容器流体之前。

这是小提琴 。