Bootstrap 4: How to create a dropdown menu with an accordion inside it?

Question

I am actually facing some problems to get an bootstrap accordion working inside a dropdown menu. I googled a lot and also find some StackOverflow threads here, but they are several years old and depending on bootstrap 3 or bootstrap 2. Like this one here: Twitter Bootstrap: How to create a dropdown button with an accordion inside it?

Can anybody help me here or have a solution for a working accordion inside a bootstrap dropdown menu.

<nav class="navbar navbar-expand-md">
  <ul class="navbar-nav">
    <li class="nav-item mega-dropdown-menu">
      <a class="nav-link" href="#" id="dropdown01" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Test</a>
      <div class="dropdown-menu" aria-labelledby="dropdown01">
        <nav class="navbar">
          <ul class="navbar-nav">
            <li class="nav-item">
              <a class="nav-link" data-toggle="collapse" href="#collapseExample" role="button" aria-expanded="false" aria- controls="collapseExample">Accordion</a>
              <div id="collapseExample" class="collapse">
                <ul class="navbar-nav">
                  <li class="nav-link">
                    <a class="nav-link" href="#">Accordion Link 1</a>
                  </li>
                  <li class="nav-link">
                    <a class="nav-link" href="#">Accordion Link 2</a>
                  </li>
                </ul>
              </div>
            </li>
          </ul>
        </nav>
      </div>
    </li>
  </ul>
</nav>

Answer 1

The trick to keeping the Navbar dropdown open on click is to use a <form> tag. Therefore if you place the accordion inside a <form> it will work as desired.

<div class="collapse navbar-collapse" id="navbarContent">
  <ul class="navbar-nav">
    <li class="nav-item dropdown">
      <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
        Dropdown
      </a>
      <div class="dropdown-menu">
        <form class="accordion" id="accordionExample">
          <div>
            <a class="nav-link" data-toggle="collapse" data-target="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
              Item #1
            </a>
            <div id="collapseOne" class="collapse px-3 show" data-parent="#accordionExample">
              Collapse 1 content
            </div>
          </div>
          <div>
            <a class="nav-link" data-toggle="collapse" data-target="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
              Item #2
            </a>
            <div id="collapseTwo" class="collapse px-3" data-parent="#accordionExample">
              Collapse 2 content...
            </div>
          </div>
          <div>
            <a class="nav-link" data-toggle="collapse" data-target="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
              Item #3
            </a>
            <div id="collapseThree" class="collapse px-3" data-parent="#accordionExample">
              Collapse 3 content...
            </div>
          </div>
        </form>
      </div>
    </li>
  </ul>
</div>

Demo: https://www.codeply.com/go/F8iQy0MeLa