er {
    position:relative;
    overflow: auto;
    height:100%;
  }

  .button-bar {
    position: absolute;
    top: 10px;
    right: 20px;
    z-index: 1; /* 确保按钮栏在内容之上 */
    border: 1px solid black;
  }

  .data{
    height: 300px;
  }
</style>
</head>
<body>
<div class="container">
  <div class="container-header">Container Header</div>
  <div class="container-body">
    <div class="container2">
      <div class="container2-header">Container2 Header</div>
      <div class="container