Bootstrap Navbar与Leaflet地图Div重叠问题解决求助

问题场景 #

给简单的Leaflet地图添加Bootstrap导航栏后，出现容器重叠问题：地图（含缩放按钮）被导航栏遮挡，地图从浏览器顶部开始渲染，而非导航栏底部。

原代码 #

<!DOCTYPE html>
<html>
    <head>
        <title>Title</title>
        <meta charset="UTF-8">
        
<!--    Leaflet-->
        <link rel="stylesheet" href="https://unpkg.com/leaflet@1.9.1/dist/leaflet.css" />
        <script src="https://unpkg.com/leaflet@1.9.1/dist/leaflet.js"></script>
        
<!--    Jquery  -->
        <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.1/jquery.min.js"></script>    
        
<!--    Bootstrap-->
        <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
        <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
        
        <style>
            html, body {height: 100%; margin: 0;}
            #map { width: 100%; height: 100%; }
        </style>
    </head>
    <body>
        
<!--    Simple Navbar-->
        <nav class="navbar navbar-expand-lg navbar-light bg-light fixed-top">       
            <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>
            <div class="collapse navbar-collapse" id="navbarSupportedContent">
                <ul class="navbar-nav mr-auto">                 
                    <li class="nav-item">
                        <select class="custom-select">
                            <optgroup label="Menu">
                                <option selected value="0">Option 0</option>
                                <option value="1">Option 1</option>
                                <option value="2">Option 2</option>
                                <option value="3">Option 3</option>
                            </optgroup>
                        </select>
                    </li>
                </ul>
            </div>
        </nav>
        
<!--    Div for my Leaflet map-->
        <div id='map'></div>

        <script>
            myMap = L.map('map')
            myMap.setView([0,0], 3)
            BgLayer = L.tileLayer('https://{s}.tile.osm.org/{z}/{x}/{y}.png')
            BgLayer.addTo(myMap)
        </script>
    </body>
</html>

效果截图 #

解决方法 #

重叠原因是fixed-top类的导航栏固定在视口顶部，不占据文档流空间，导致地图从顶部开始渲染。以下两种Bootstrap适配方案可解决：

方案一：适配固定导航栏的内边距与地图高度 #

1. 给<body>添加Bootstrap内边距类pt-5（对应顶部内边距3rem，适配默认56px高度的导航栏，可根据实际导航栏高度调整为pt-4等），避免地图顶部被遮挡。
2. 修改地图容器的CSS高度，用calc(100vh - 56px)替代100%，确保地图高度为视口高度减去导航栏高度，不会超出视口。

修改后的完整代码：

<!DOCTYPE html>
<html>
    <head>
        <title>Title</title>
        <meta charset="UTF-8">
        
<!--    Leaflet-->
        <link rel="stylesheet" href="https://unpkg.com/leaflet@1.9.1/dist/leaflet.css" />
        <script src="https://unpkg.com/leaflet@1.9.1/dist/leaflet.js"></script>
        
<!--    Jquery  -->
        <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.1/jquery.min.js"></script>    
        
<!--    Bootstrap-->
        <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
        <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
        
        <style>
            html, body {height: 100%; margin: 0;}
            #map { width: 100%; height: calc(100vh - 56px); }
        </style>
    </head>
    <body class="pt-5">
        
<!--    Simple Navbar-->
        <nav class="navbar navbar-expand-lg navbar-light bg-light fixed-top">       
            <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>
            <div class="collapse navbar-collapse" id="navbarSupportedContent">
                <ul class="navbar-nav mr-auto">                 
                    <li class="nav-item">
                        <select class="custom-select">
                            <optgroup label="Menu">
                                <option selected value="0">Option 0</option>
                                <option value="1">Option 1</option>
                                <option value="2">Option 2</option>
                                <option value="3">Option 3</option>
                            </optgroup>
                        </select>
                    </li>
                </ul>
            </div>
        </nav>
        
<!--    Div for my Leaflet map-->
        <div id='map'></div>

        <script>
            myMap = L.map('map')
            myMap.setView([0,0], 3)
            BgLayer = L.tileLayer('https://{s}.tile.osm.org/{z}/{x}/{y}.png')
            BgLayer.addTo(myMap)
        </script>
    </body>
</html>

方案二：改用粘性导航栏 #

如果不需要导航栏始终固定在顶部，可将导航栏的fixed-top类替换为sticky-top。该类会让导航栏在文档流中占据空间，滚动到顶部时自动固定，地图会自动从导航栏下方开始渲染，无需额外调整样式：

<nav class="navbar navbar-expand-lg navbar-light bg-light sticky-top">

内容的提问来源于stack exchange，提问作者Lucien S.