html - 如何让 Box-Shadow 在另一个元素上方渲染？

Question

这个问题在这里已经有了答案:

Understanding z-index stacking order (1 个回答)

How does the z-index property really work? (5 个回答)

关闭 2年前。

我有以下代码:

body {
  margin: 0px;
  padding: 0px;
}

a {
  text-decoration: none;
  color: black;
}

a:visited {
  color: black;
}

#superheader {
  width: auto;
  height: 100px;
  position: relative;
}

#superheader p {
  font-family: Sansation;
  font-size: 50px;
  display: block;
  line-height: 0.0
}

#superheader table {
  border: none;
  height: 100px;
  display: block;
}

#header {
  height: 140px;
  box-shadow: 0em 0em 1em 0.2em grey;
  position: relative;
  background-color: #E6E6E6;
  padding-left: 70px;
  padding-right: 70px;
  font-family: sans-serif;
}

.menuelement {
  width: 100px;
  height: 40px;
  text-align: center;
  padding-left: 10px;
  padding-right: 10px;
  float: left;
  position: relative;

}

.menuelement:hover {
  background-color: dimgrey;
  color: lightgray;
}

#header>a {
  line-height: 2.5;
}

#page {
  background-color: white;
  font-family: sans-serif;
  margin-left: 70px;
  margin-right: 70px;
  height: 100%;
  margin-bottom: 2em;
  box-shadow: 0em 0.6em 0.5em grey;
  padding-left: 2em;
  padding-right: 2em;
  padding-top: 0.1em;
  height: 6000px;
  position: relative;
}

<div id="header">
  <div id="superheader">
    <div style="margin: auto; width: 630px;">
      <table>
        <tr>
          <td><img src="images/memoji.png" width="100px" height="100px" alt="Icon" </td> <td>
            <p>Title</p>
          </td>
        </tr>
      </table>
    </div>
  </div>
  <a href="page1.html">
    <div class="menuelement">page1</div>
  </a>
  <a href="index.html">
    <div class="menuelement">Startseite</div>
  </a>
  <a href="page2.html">
    <div class="menuelement">page2</div>
  </a>
</div>
<div id="page">
  <h1>First Headline</h1>
  <h2>Second Headline</h2>
  <p>Some text.</p>
</div>

header-div 的 box-shadow 不在 page-div 上方呈现，而是隐藏在其下方。
如何让 box-shadow 呈现在 page-div 上，以便在那里可见？
非常感谢您帮助我!

Answer 1

box-shadow header 被 page 选择器隐藏，因为 header 选择器堆栈顺序低于 page 选择器。

所以需要修改header选择器的栈顺序高于page选择器。

这可以使用 z-index 来完成。并将 z-index: 1 (任何高于 0 的值，因为默认 z-index: auto (= 0))添加到 #header 类，你会看到 box-shadow.

body {
  margin: 0px;
  padding: 0px;
}

a {
  text-decoration: none;
  color: black;
}

a:visited {
  color: black;
}

#superheader {
  width: auto;
  height: 100px;
  position: relative;
}

#superheader p {
  font-family: Sansation;
  font-size: 50px;
  display: block;
  line-height: 0.0
}

#superheader table {
  border: none;
  height: 100px;
  display: block;
}

#header {
  height: 140px;
  box-shadow: 0em 0em 1em 0.2em grey;
  position: relative;
  background-color: #E6E6E6;
  padding-left: 70px;
  padding-right: 70px;
  font-family: sans-serif;
  
  z-index: 5;
}

.menuelement {
  width: 100px;
  height: 40px;
  text-align: center;
  padding-left: 10px;
  padding-right: 10px;
  float: left;
  position: relative;

}

.menuelement:hover {
  background-color: dimgrey;
  color: lightgray;
}

#header>a {
  line-height: 2.5;
}

#page {
  background-color: white;
  font-family: sans-serif;
  margin-left: 70px;
  margin-right: 70px;
  height: 100%;
  margin-bottom: 2em;
  box-shadow: 0em 0.6em 0.5em grey;
  padding-left: 2em;
  padding-right: 2em;
  padding-top: 0.1em;
  height: 6000px;
  position: relative;
}

<div id="header">
  <div id="superheader">
    <div style="margin: auto; width: 630px;">
      <table>
        <tr>
          <td><img src="images/memoji.png" width="100px" height="100px" alt="Icon" </td> <td>
            <p>Title</p>
          </td>
        </tr>
      </table>
    </div>
  </div>
  <a href="page1.html">
    <div class="menuelement">page1</div>
  </a>
  <a href="index.html">
    <div class="menuelement">Startseite</div>
  </a>
  <a href="page2.html">
    <div class="menuelement">page2</div>
  </a>
</div>
<div id="page">
  <h1>First Headline</h1>
  <h2>Second Headline</h2>
  <p>Some text.</p>
</div>