html - 单击时如何保持打开的 mdl 菜单与 html 选择？

Question

这是所发生情况的示例，当单击菜单中的下拉列表时，菜单将被关闭。提前致谢

#menu{
    margin: 0 auto; 
}

<link href="https://code.getmdl.io/1.3.0/material.light_blue-blue.min.css" rel="stylesheet"/>
<script src="https://code.getmdl.io/1.3.0/material.min.js"></script>

<nav class="mdl-navigation">
   <button id="menu" class="mdl-button mdl-js-button mdl-button--icon"     style="background-color:blue">
   </button>
   <ul class="mdl-menu mdl-menu--bottom-right mdl-js-menu mdl-js-ripple-effect" for="menu" id="ul_container">
       <p>DropDownList</p>
          <li>
             <select name="Select">
                <option value="0">Option_0</option>
                <option value="1">Option_1</option>
                <option value="2">Option_2</option>
                <option value="3">Option_3</option>
                <option value="4">Option_4</option>
                <option value="5">Option_5</option>
             </select>
          </li> 
   </ul>      
</nav>

Answer 1

document.querySelector('.mdl-menu').addEventListener('click', function(event) {
  event.stopPropagation();
});

document.querySelector('.mdl-menu').addEventListener('click', function(event) {
  event.stopPropagation();
});

#menu{
    margin: 0 auto; 
}

<link href="https://code.getmdl.io/1.3.0/material.light_blue-blue.min.css" rel="stylesheet"/>
<script src="https://code.getmdl.io/1.3.0/material.min.js"></script>

<nav class="mdl-navigation">
   <button id="menu" class="mdl-button mdl-js-button mdl-button--icon"     style="background-color:blue">
   </button>
   <ul class="mdl-menu mdl-menu--bottom-right mdl-js-menu mdl-js-ripple-effect" for="menu" id="ul_container">
       <p>DropDownList</p>
          <li>
             <select name="Select">
                <option value="0">Option_0</option>
                <option value="1">Option_1</option>
                <option value="2">Option_2</option>
                <option value="3">Option_3</option>
                <option value="4">Option_4</option>
                <option value="5">Option_5</option>
             </select>
          </li> 
   </ul>      
</nav>