要将弹性项目与Bootstrap 4对齐，请使用.align-self-center类。
以下是我的flex的div-
<div class="d-flex bg-primary" style="height:200px">
现在添加弹性项目，在这里我在第三个弹性项目上应用了align-self-center类-
<div class="d-flex bg-primary" style="height:200px"> <div class="p-2 border">A-one</div> <div class="p-2 border">B-one</div> <div class="p-2 border align-self-center">C-one</div> <div class="p-2 border">D-one</div> </div>
您可以尝试运行以下代码以在Bootstrap中实现align-self-center类：
<!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"> <h1>Align Specific Flex Item in the center</h1> <div class="d-flex bg-primary" style="height:200px"> <div class="p-2 border">A-one</div> <div class="p-2 border">B-one</div> <div class="p-2 border align-self-center">C-one</div> <div class="p-2 border">D-one</div> </div> </div> </body> </html>