如何让 Bootstrap 下拉菜单显示在粘性 table headers 前面？

Question

我按照 CSS Tricks tutorial 获得了带有粘性 header 和第一列的 table，并尝试在第一列内添加 Bootstrap 下拉列表。

问题是，下拉列表显示在 parent 单元格的前面，但在第一列的所有其他单元格后面：

我试过将单元格的位置更改为相对位置，将下拉菜单的 z-index 切换为更高的值，但下拉菜单仍位于第一列之后。

这是一个 JSFiddle，其中包含一个最小的、可重现的示例：https://jsfiddle.net/maxencelav/hwsrcmL6/14/

@import url("https://fonts.googleapis.com/css2?family=Fraunces:ital,wght@0,700;1,200&display=swap");
table {
  font-family: "Fraunces", serif;
  font-size: 125%;
  white-space: nowrap;
  margin: 3px;
  border: none;
  border-collapse: separate;
  border-spacing: 0;
  table-layout: fixed;
  border: 1px solid black;
}

table td,
table th {
  border: 1px solid black;
  padding: 0.5rem 1rem;
}

table thead th {
  padding: 3px;
  position: sticky;
  top: 0;
  z-index: 1;
  width: 25vw;
  background: white;
}

table td {
  background: #fff;
  padding: 4px 5px;
  text-align: center;
}

table tbody th {
  font-weight: 100;
  font-style: italic;
  text-align: left;
  position: relative;
}

table thead th:first-child {
  position: sticky;
  left: 0;
  z-index: 2;
}

table tbody th {
  position: sticky;
  left: 0;
  background: white;
  z-index: 1;
}

caption {
  text-align: left;
  padding: 0.25rem;
  position: sticky;
  left: 0;
}

[role="region"][aria-labelledby][tabindex] {
  width: 100%;
  max-height: 98vh;
  overflow: auto;
}

#team-cell-container {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  margin: 0;
  gap: 5px;
}

<script src="https://code.jquery.com/jquery-3.4.1.slim.js"></script>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.js"></script>
<link href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.css" rel="stylesheet" />


<!-- Based off https://css-tricks.com/a-table-with-both-a-sticky-header-and-a-sticky-first-column/ -->

<table>
  <thead>
    <tr>
      <th>Teams</th>
      <th>1</th>
      <th>2</th>
      <th>3</th>
      <th>4</th>
      <th>5</th>
      <th>6</th>
      <th>7</th>
      <th>8</th>
      <th>9</th>
      <th>Runs</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>
        <div id="team-cell-container">
          Milwaukee Brewers
          <div class="dropdown">
            <i class="fa fa-cog" type="button" id="dropdown-item" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"></i>
            <div class="dropdown-menu" aria-labelledby="dropdown-item">
              <a class="dropdown-item" href="#">Action</a>
              <a class="dropdown-item" href="#">Another action</a>
              <a class="dropdown-item" href="#">Something else here</a>
            </div>
          </div>
        </div>
      </th>
      <td>2</td>
      <td>1</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>1</td>
      <td>1</td>
      <td>0</td>
      <td>1</td>
      <td>13</td>
    </tr>
    <tr>
      <th>Los Angles Dodgers</th>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>3</td>
      <td>2</td>
      <td>4</td>
      <td>2</td>
      <td>3</td>
      <td>20</td>
    </tr>
    <tr>
      <th>New York Mets</th>
      <td>0</td>
      <td>1</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>2</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>12</td>
    </tr>
    <tr>
      <th>St. Louis Cardinals</th>
      <td>3</td>
      <td>4</td>
      <td>1</td>
      <td>3</td>
      <td>2</td>
      <td>4</td>
      <td>3</td>
      <td>2</td>
      <td>3</td>
      <td>25</td>
    </tr>
  </tbody>
</table>

Answer 1

这是 CSS position 和 z-index 的问题。由 this question. (Or see my testing) 解释。

要使 position: absolute 高 z-index 出现在其他亲属之上，您必须将其他人的 z-index 设置为低于父级的 z-index落下。这证实了 this answer.

的工作

首先，为您的 table 添加一些身份。

<!-- Based off https://css-tricks.com/a-table-with-both-a-sticky-header-and-a-sticky-first-column/ -->

<table id="my-table">
  <thead>
    <tr>
      <th>Teams</th>
      <th>1</th>
      <th>2</th>
      <th>3</th>
      <th>4</th>
      <th>5</th>
      <th>6</th>
      <th>7</th>
      <th>8</th>
      <th>9</th>
      <th>Runs</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>
        <div id="team-cell-container">
          Milwaukee Brewers
          <div class="dropdown">
            <i class="fa fa-cog" type="button" id="dropdown-item" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"></i>
            <div class="dropdown-menu" aria-labelledby="dropdown-item">
              <a class="dropdown-item" href="#">Action</a>
              <a class="dropdown-item" href="#">Another action</a>
              <a class="dropdown-item" href="#">Something else here</a>
            </div>
          </div>
        </div>
      </th>
      <td>2</td>
      <td>1</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>1</td>
      <td>1</td>
      <td>0</td>
      <td>1</td>
      <td>13</td>
    </tr>
    <tr>
      <th>Los Angles Dodgers</th>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>3</td>
      <td>2</td>
      <td>4</td>
      <td>2</td>
      <td>3</td>
      <td>20</td>
    </tr>
    <tr>
      <th>New York Mets</th>
      <td>0</td>
      <td>1</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>2</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>12</td>
    </tr>
    <tr>
      <th>St. Louis Cardinals</th>
      <td>3</td>
      <td>4</td>
      <td>1</td>
      <td>3</td>
      <td>2</td>
      <td>4</td>
      <td>3</td>
      <td>2</td>
      <td>3</td>
      <td>25</td>
    </tr>
    <tr>
      <th>Houston Astros</th>
      <td>3</td>
      <td>2</td>
      <td>1</td>
      <td>4</td>
      <td>2</td>
      <td>3</td>
      <td>1</td>
      <td>3</td>
      <td>1</td>
      <td>20</td>
    </tr>
    <tr>
      <th>Toronto Blue Jays</th>
      <td>2</td>
      <td>4</td>
      <td>4</td>
      <td>1</td>
      <td>1</td>
      <td>2</td>
      <td>3</td>
      <td>4</td>
      <td>1</td>
      <td>22</td>
    </tr>
    <tr>
      <th>Boston Red Sox</th>
      <td>4</td>
      <td>4</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>0</td>
      <td>0</td>
      <td>1</td>
      <td>1</td>
      <td>17</td>
    </tr>
    <tr>
      <th>Chicago Cubs</th>
      <td>1</td>
      <td>1</td>
      <td>0</td>
      <td>0</td>
      <td>2</td>
      <td>2</td>
      <td>2</td>
      <td>0</td>
      <td>4</td>
      <td>12</td>
    </tr>
    <tr>
      <th>Philadelphia Phillies</th>
      <td>0</td>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>4</td>
      <td>1</td>
      <td>0</td>
      <td>4</td>
      <td>2</td>
      <td>17</td>
    </tr>
    <tr>
      <th>Chicago White Sox</th>
      <td>2</td>
      <td>0</td>
      <td>2</td>
      <td>3</td>
      <td>4</td>
      <td>2</td>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>19</td>
    </tr>
    <tr>
      <th>San Diego Padres</th>
      <td>2</td>
      <td>2</td>
      <td>3</td>
      <td>0</td>
      <td>4</td>
      <td>2</td>
      <td>2</td>
      <td>0</td>
      <td>2</td>
      <td>17</td>
    </tr>
    <tr>
      <th>Cleveland Indians</th>
      <td>1</td>
      <td>0</td>
      <td>0</td>
      <td>3</td>
      <td>2</td>
      <td>1</td>
      <td>3</td>
      <td>1</td>
      <td>0</td>
      <td>11</td>
    </tr>
    <tr>
      <th>San Francisco Giants</th>
      <td>1</td>
      <td>3</td>
      <td>1</td>
      <td>4</td>
      <td>1</td>
      <td>1</td>
      <td>1</td>
      <td>2</td>
      <td>3</td>
      <td>17</td>
    </tr>
    <tr>
      <th>Cincinatti Reds</th>
      <td>2</td>
      <td>2</td>
      <td>4</td>
      <td>1</td>
      <td>4</td>
      <td>2</td>
      <td>2</td>
      <td>3</td>
      <td>3</td>
      <td>23</td>
    </tr>
    <tr>
      <th>Minnesota Twins</th>
      <td>4</td>
      <td>4</td>
      <td>1</td>
      <td>0</td>
      <td>2</td>
      <td>0</td>
      <td>3</td>
      <td>1</td>
      <td>3</td>
      <td>18</td>
    </tr>
    <tr>
      <th>Tampa Bay Rays</th>
      <td>4</td>
      <td>1</td>
      <td>3</td>
      <td>0</td>
      <td>2</td>
      <td>1</td>
      <td>4</td>
      <td>0</td>
      <td>1</td>
      <td>16</td>
    </tr>
    <tr>
      <th>Miami Marlins</th>
      <td>0</td>
      <td>3</td>
      <td>0</td>
      <td>4</td>
      <td>3</td>
      <td>3</td>
      <td>0</td>
      <td>1</td>
      <td>4</td>
      <td>18</td>
    </tr>
    <tr>
      <th>Oakland Athletics</th>
      <td>3</td>
      <td>3</td>
      <td>2</td>
      <td>0</td>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>1</td>
      <td>0</td>
      <td>15</td>
    </tr>
    <tr>
      <th>Detroit Tigers</th>
      <td>3</td>
      <td>4</td>
      <td>1</td>
      <td>2</td>
      <td>3</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>4</td>
      <td>19</td>
    </tr>
    <tr>
      <th>Pittsburgh Pirates</th>
      <td>2</td>
      <td>2</td>
      <td>0</td>
      <td>3</td>
      <td>0</td>
      <td>2</td>
      <td>2</td>
      <td>2</td>
      <td>2</td>
      <td>15</td>
    </tr>
    <tr>
      <th>Seattle Mariners</th>
      <td>1</td>
      <td>3</td>
      <td>3</td>
      <td>1</td>
      <td>2</td>
      <td>2</td>
      <td>0</td>
      <td>4</td>
      <td>0</td>
      <td>16</td>
    </tr>
    <tr>
      <th>Atlanta Braves</th>
      <td>4</td>
      <td>3</td>
      <td>0</td>
      <td>3</td>
      <td>4</td>
      <td>4</td>
      <td>4</td>
      <td>4</td>
      <td>3</td>
      <td>29</td>
    </tr>
  </tbody>
</table>
</div>

然后使用 Bootstrap dropdown events 监听显示或隐藏下拉列表元素。

$('#my-table .dropdown').on('show.bs.dropdown', (event) => {
    let thisTable = event.target.closest('table');
    thisTable.classList.add('dropdowns-opened');
    // add class to all <tr>
    $(thisTable).find('tr').addClass('non-dropdown');
    // remove class of this <tr>
    event.target.closest('tr').classList.remove('non-dropdown');
});

$('#my-table .dropdown').on('hidden.bs.dropdown', (event) => {
    let thisTable = event.target.closest('table');
    thisTable.classList.remove('dropdowns-opened');
    $(thisTable).find('tr').removeClass('non-dropdown');
});

上面的JavaScript将在下拉元素显示或隐藏时添加和删除class。

现在，添加一些 CSS class 使下拉菜单显示在其他菜单之上。

table.dropdowns-opened tbody tr.non-dropdown th {
    z-index: 0;
}

See it in action on JsFiddle.

如果粘性功能不起作用，您可以将当前的 z-index: 1 更改为 2，并使用上面的 class 从 z-index: 0 更改为 1预期。

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