以下实例演示了 center 的使用 - 在线编辑器

<!DOCTYPE html>
<html>
<head>
  <style>
    .flex-container {
      display: -webkit-flex;
      display: flex;
      -webkit-align-items: center;
      align-items: center;
      width: 400px;
      height: 250px;
      background-color: lightgrey;
    }

    .flex-item {
      background-color: cornflowerblue;
      width: 100px;
      margin: 10px;
    }
  </style>
</head>
<body>

  <div class="flex-container">
    <div class="flex-item">flex item 1</div>
    <div class="flex-item">flex item 2</div>
    <div class="flex-item">flex item 3</div>
  </div>

</body>
</html>
​x
 
<!DOCTYPE html>
<html>
<head>
  <style>
    .flex-container {
      display: -webkit-flex;
      display: flex;
      -webkit-align-items: center;
      align-items: center;
      width: 400px;
      height: 250px;
      background-color: lightgrey;
    }
​
    .flex-item {
      background-color: cornflowerblue;
      width: 100px;
      margin: 10px;
    }
  </style>
</head>
<body>
​
  <div class="flex-container">
    <div class="flex-item">flex item 1</div>
    <div class="flex-item">flex item 2</div>
    <div class="flex-item">flex item 3</div>
  </div>
​
</body>
</html>