HTML
CSS
JavaScript
HTML
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>可扩展面板 - 默认打开的面板项</title>
  <link rel="stylesheet" href="https://cdn.w3cbus.com/library/mdui/1.0.2/css/mdui.min.css"/>
</head>
<body>

  <div class="mdui-container">
    <div class="mdui-panel" mdui-panel>
      <div class="mdui-panel-item">
        <div class="mdui-panel-item-header">First</div>
        <div class="mdui-panel-item-body">
          <p>First content</p>
          <p>First content</p>
          <p>First content</p>
          <p>First content</p>
          <p>First content</p>
          <p>First content</p>
        </div>
      </div>
      <div class="mdui-panel-item mdui-panel-item-open">
        <div class="mdui-panel-item-header">Second</div>
        <div class="mdui-panel-item-body">
          <p>Second content</p>
          <p>Second content</p>
          <p>Second content</p>
          <p>Second content</p>
          <p>Second content</p>
          <p>Second content</p>
        </div>
      </div>
      <div class="mdui-panel-item">
        <div class="mdui-panel-item-header">Third</div>
        <div class="mdui-panel-item-body">
          <p>Third content</p>
          <p>Third content</p>
          <p>Third content</p>
          <p>Third content</p>
          <p>Third content</p>
          <p>Third content</p>
        </div>
      </div>
    </div>
  </div>

  <script src="https://cdn.w3cbus.com/library/mdui/1.0.2/js/mdui.min.js"></script>
</body>
</html>
CSS

  
JavaScript