要允许将flex项目包装在不同的屏幕上，请使用flex-*-wrap类。适用于各种屏幕尺寸的柔性包装适用于小，中，大和超大屏幕。
例如，使用flex-lg-wrap类在大屏幕上包装flex项目-
<div class="d-flex flex-lg-wrap bg-primary">
对于小屏幕-
<div class="d-flex flex-sm-wrap bg-primary">
您可以尝试运行以下代码来实现flex-*-wrap类，以在小屏幕和大屏幕尺寸上包装flex项目-
<!DOCTYPE html> <html lang="en"> <head> <title>Bootstrap Example</title> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css"> <script src="https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script> </head> <body> <div class="container mt-3"> <h3>Flex Examples</h3> <p>Wrap - Yes</p> <div class="d-flex flex-wrap bg-primary"> <div class="p-2 border">Poland</div> <div class="p-2 border">Netherlands</div> <div class="p-2 border">Ireland</div> <div class="p-2 border">Brazil</div> <div class="p-2 border">India</div> <div class="p-2 border">US</div> <div class="p-2 border">Bangladesh</div> <div class="p-2 border">Russia</div> <div class="p-2 border">Morocco</div> <div class="p-2 border">UK</div> <div class="p-2 border">Australia</div> <div class="p-2 border">Denmark</div> </div> <br> <p>Will wrap on Small Screen</p> <div class="d-flex flex-sm-wrap bg-primary"> <div class="p-2 border">Poland</div> <div class="p-2 border">Netherlands</div> <div class="p-2 border">Ireland</div> <div class="p-2 border">Brazil</div> <div class="p-2 border">India</div> <div class="p-2 border">US</div> <div class="p-2 border">Bangladesh</div> <div class="p-2 border">Russia</div> <div class="p-2 border">Morocco</div> <div class="p-2 border">UK</div> <div class="p-2 border">Australia</div> <div class="p-2 border">Denmark</div> </div><br> <p>Will Wrap on Large Screen</p> <div class="d-flex flex-lg-wrap bg-primary"> <div class="p-2 border">Poland</div> <div class="p-2 border">Netherlands</div> <div class="p-2 border">Ireland</div> <div class="p-2 border">Brazil</div> <div class="p-2 border">India</div> <div class="p-2 border">US</div> <div class="p-2 border">Bangladesh</div> <div class="p-2 border">Russia</div> <div class="p-2 border">Morocco</div> <div class="p-2 border">UK</div> <div class="p-2 border">Australia</div> <div class="p-2 border">Denmark</div> </div><br> </div> </body> </html>