在Bootstrap 4的不同屏幕上的中间对齐一个flex项目

要在Bootstrap 4的不同屏幕上的中心对齐弹性项目，请使用.align-self-*-center类。

在小，中，大等不同的屏幕上进行设置-

在小屏幕的中央对齐一个弹性项目

<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-sm-center">C-one</div>
  <div class="p-2 border">D-one</div>
</div>

在中间屏幕的中央对齐一个弹性项目

<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-md-center">C-one</div>
  <div class="p-2 border">D-one</div>
</div>

将弹性项目在大屏幕的中央对齐

<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-lg-center">C-one</div>
  <div class="p-2 border">D-one</div>
</div>

让我们看一个示例，以在不同屏幕的中心对齐弹性项目-

示例

<!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>
    <h2>Small Screen Size</h2>
    <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-sm-center">C-one</div>
      <div class="p-2 border">D-one</div>
    </div>
    <h2>Medium Screen Size</h2>
    <div class="d-flex bg-secondary" 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-md-center">C-one</div>
      <div class="p-2 border">D-one</div>
    </div>
    <h2>Large Screen Size</h2>
    <div class="d-flex bg-info" 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-lg-center">C-one</div>
      <div class="p-2 border">D-one</div>
    </div>
  </div>

</body>
</html>

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