Question

我只是迁移到Bootstrap V4。我自定义了初学者模板：https://v4-alpha.getbootstrap.com/examples/starter-template/

我希望navbar透明但在viewport为sm和xs时变为黑暗。

我尝试使用断点更改它并添加'navbar-custom'类，但我没有更改

html {
    overflow: hidden;
    height: 100%;
    
 }



body {
  padding-top: 5rem;
  overflow: auto;
  height:  100%;

  background: linear-gradient(-45deg, #E8D1E2, #7CC4FF, #FFECBD, #BF9BFA);
  	background-size: 400% 400%;
  	-webkit-animation: Gradient 15s ease infinite;
  	-moz-animation: Gradient 15s ease infinite;
  	animation: Gradient 15s ease infinite;
 }

@-webkit-keyframes Gradient {
  0% {
    background-position: 0% 50%
  }
  50% {
    background-position: 100% 50%
  }
  100% {
    background-position: 0% 50%
  }
}

@-moz-keyframes Gradient {
  0% {
    background-position: 0% 50%
  }
  50% {
    background-position: 100% 50%
  }
  100% {
    background-position: 0% 50%
  }
}

@keyframes Gradient {
  0% {
    background-position: 0% 50%
  }
  50% {
    background-position: 100% 50%
  }
  100% {
    background-position: 0% 50%
  }

}



.navbar {
	border-top: 2px solid #C66FF4;
	width: 100%
}

@media (min-width: 768px) {
  
  nav .navbar .navbar-custom {
    background: rgba(0,0,0,0);

  }
}

.starter-template {
  padding: 3rem 1.5rem;
  text-align: center;
}

<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<meta name="viewport" content="width=device-width, initial-scale=1 shrink-to-fit=no">
	<meta name="description" content="Full-Stack Graphic Designer, Illustrator, Front-End Development">
	<meta name="author" content="Liliana Orozco">
	<meta name="keywords" content="Designer, Creativity, Design, CSS, HTML5, Branding, Logotype, Illustration, Web, Advertising">
	<title>Randomood says: Welcome!</title>

	<!-- Bootstrap 4.0 cdn -->
	<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" integrity="sha384-/Y6pD6FV/Vv2HJnA6t+vslU6fwYXjCFtcEpHbNJ0lyAFsXTsjBbfaDjzALeQsN6M" crossorigin="anonymous">


	<!--custom styles for this page -->
	<link href="css/home.css" rel="stylesheet">


</head>
<body>
	

	<!--navigation-->
    <nav class="navbar navbar-expand-md navbar-dark bg-dark fixed-top  navbar-custom">

    
   

    
    <!--Brand in navigation menu-->		
      
      <a class="navbar-brand " href="#">Randomood</a>
     <!--Brand image in navigation menu-->
     <a class="navbar-brand" href="#"><img></a>

      <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarsExampleDefault" aria-controls="navbarsExampleDefault" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
      </button>

      <div class="collapse navbar-collapse" id="navbarsExampleDefault">
        <ul class="navbar-nav ml-auto">
          
          <li class="nav-item">
            <a class="nav-link" href="#">Book</a>
          </li>
          <li class="nav-item">
            <a class="nav-link" href="#">About</a>
          </li>
          <li class="nav-item">
            <a class="nav-link" href="#">Contact</a>
          </li>
          
           
        </ul>
        
      </div>
    </nav>

    <div class="container">

      <div class="starter-template">
        <h1>Bootstrap starter template</h1>
        <p class="lead">Use this document as a way to quickly start any new project.<br> All you get is this text and a mostly barebones HTML document.</p>
      </div>

    </div><!-- /.container -->





	<!--JS, Popper and JQuery-->
	<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
	<script>window.jQuery || document.write('<script src="jquery-slim.min.js"><\/script>')</script>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.11.0/umd/popper.min.js" integrity="sha384-b/U6ypiBEHpOf/4+1nzFpr53nxSS+GLCkfwBdFNTxtclqqenISfwAzpKaMNFNmj4" crossorigin="anonymous"></script>
	<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/js/bootstrap.min.js" integrity="sha384-h0AbiXch4ZDo7tp9hKZ4TsHbi047NrKGLO3SEJAg45jXxnGIfYzk4Si90RDIqNm1" crossorigin="anonymous"></script>
</body>

Answer 1

您正在.bg-dark中使用Bootstrap的<nav>课程。这个类的CSS声明是：

.bg-dark {
    background-color: #343a40!important;
}

因此，您不能覆盖background-color属性。要在特定屏幕断点处更改background-color属性，请使用Javascript或Jquery删除.bg-dark类，并添加更改background-color <nav>属性的自定义类。我希望你的解释清楚。

Answer 2

在引导程序主题中使用scss轻松覆盖：

.bg-dark {
    background-color: #343a40;
    @include media-breakpoint-up(sm) {
        background-color: transparent;
    }
}

当视口大小更改Bootstrap v4时更改导航栏颜色

2 个答案: