源代码 ：
点击运行
<!DOCTYPE html> <html> <head> <title>Bootstrap 实例</title> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/css/bootstrap.min.css"> <script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script> <script src="https://cdn.staticfile.org/popper.js/1.15.0/umd/popper.min.js"></script> <script src="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/js/bootstrap.min.js"></script> </head> <body> <div class="container mt-3"> <h2>水平方向</h2> <p>.flex-row 可以设置弹性子元素水平显示(默认)。</p> <p>使用 .flex-sm|md|lg|xl-row 可以适应不同屏幕设置。重置浏览器查看效果。</p> <p><code>flex-row:</code></p> <div class="d-flex flex-row bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> <p><code>flex-sm-row:</code></p> <div class="d-sm-flex flex-sm-row bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> <p><code>flex-md-row:</code></p> <div class="d-md-flex flex-md-row bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> <p><code>flex-lg-row:</code></p> <div class="d-lg-flex flex-lg-row bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> <p><code>flex-xl-row:</code></p> <div class="d-xl-flex flex-xl-row bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> </div> </body> </html>
运行结果