html - 使用 CSS 中的属性 'position' 优先考虑两个元素之一

Question

我正在做一个元素，我遇到了一个问题。通常在普通屏幕上，当我将头像悬停在搜索栏旁边时，我的工作看起来像这样:

问题发生在我使用小屏幕时，包含“我的帐户”、“我的心愿单”和“注销”按钮的“下拉菜单”在我点击或点击头像时不会出现:

HTML/CSS 代码看起来是这样的(它已被简化以检测我容易犯的错误):

/*Avatar - Dropdown menu*/
.header-user-menu {
  float: right;
  position: relative;
  background-color: #3a3c3e;
  width: 75px;
  height: 40px;
  border-radius: 2px;
}
.header-user-menu:before {
  content: '';
  width: 0;
  height: 0;
  top: 18px;
  left: 15px;
  position: absolute;
  border: 5px solid transparent;
  border-top-color: #fff;
}
.header-user-menu ul {
  display: none;
  font: bold 13px Arial, Helvetica, sans-serif;
  background-color: inherit;
  list-style: none;
  position: absolute;
  text-align: center;
  width: 125px;
  top: 25px;
  right: 0;
  padding: 10px;
  border-radius: 2px;
  box-shadow: 0 2px 2px rgba(0, 0, 0, 0.1);
  box-sizing: border-box;
}
.header-user-menu:active ul,
.header-user-menu:hover ul,
.header-user-menu.show ul {
  display: block;
}
.header-user-menu img {
  border-radius: 50%;
  position: absolute;
  top: 6px;
  max-width: 28px;
  right: 10px;
}
/*Search Bar*/
.container-1 {
  width: 250px;
  vertical-align: middle;
  white-space: nowrap;
  position: relative;
  float: right;
  margin-right: 10px;
}
.container-1 input#search {
  width: 250px;
  height: 40px;
  background: #3a3c3e;
  border: none;
  font-size: 10pt;
  float: left;
  color: #63717f;
  padding-left: 45px;
  -webkit-border-radius: 5px;
  -moz-border-radius: 5px;
  border-radius: 5px;
}

<div class="header-first-bar">
  <div class="header-limiter">
    <div class="header-user-menu">
      <img src="images/avatar.jpg" alt="User Image" />
      <ul>
        <li><a href="account.php">My account</a>
        </li>
        <li><a href="#">My wishlist</a>
        </li>
        <li><a href="logout.php" class="highlight">Logout</a>
        </li>
      </ul>
    </div>
    <div class="container-1">
      <span class="icon"><i class="fa fa-search"></i></span>
      <input type="search" id="search" placeholder="Search..." />
    </div>
  </div>
</div>

请帮我找出我的代码有什么问题。谢谢

Answer 1

这是由于 .container-1 和 .header-user-menu 元素的 z-index。 z-index 适用于定位元素并指定元素在 z 轴上的位置。

For a positioned box, the 'z-index' property specifies:

• The stack level of the box in the current stacking context.
• Whether the box establishes a stacking context.

指定堆栈级别:“z-index”属性 https://www.w3.org/TR/CSS2/visuren.html#z-index

z-index 生效是因为 .container-1 和 .header-user-menu 有 position 设置为相对。因为 .container-1 在标记中出现在 .header-user-menu 之后，所以 z-index 更高。

要解决这个问题，您可以从 .container-1 中删除 position: relative;，因为它似乎不需要。

/*Avatar - Dropdown menu*/
.header-user-menu {
  float: right;
  position: relative;
  background-color: #3a3c3e;
  width: 75px;
  height: 40px;
  border-radius: 2px;
}
.header-user-menu:before {
  content: '';
  width: 0;
  height: 0;
  top: 18px;
  left: 15px;
  position: absolute;
  border: 5px solid transparent;
  border-top-color: #fff;
}
.header-user-menu ul {
  display: none;
  font: bold 13px Arial, Helvetica, sans-serif;
  background-color: inherit;
  list-style: none;
  position: absolute;
  text-align: center;
  width: 125px;
  top: 25px;
  right: 0;
  padding: 10px;
  border-radius: 2px;
  box-shadow: 0 2px 2px rgba(0, 0, 0, 0.1);
  box-sizing: border-box;
}
.header-user-menu:active ul,
.header-user-menu:hover ul,
.header-user-menu.show ul {
  display: block;
}
.header-user-menu img {
  border-radius: 50%;
  position: absolute;
  top: 6px;
  max-width: 28px;
  right: 10px;
}
/*Search Bar*/
.container-1 {
  width: 250px;
  vertical-align: middle;
  white-space: nowrap;
  float: right;
  margin-right: 10px;
}
.container-1 input#search {
  width: 250px;
  height: 40px;
  background: #3a3c3e;
  border: none;
  font-size: 10pt;
  float: left;
  color: #63717f;
  padding-left: 45px;
  -webkit-border-radius: 5px;
  -moz-border-radius: 5px;
  border-radius: 5px;
}

<div class="header-first-bar">
  <div class="header-limiter">
    <div class="header-user-menu">
      <img src="images/avatar.jpg" alt="User Image" />
      <ul>
        <li><a href="account.php">My account</a>
        </li>
        <li><a href="#">My wishlist</a>
        </li>
        <li><a href="logout.php" class="highlight">Logout</a>
        </li>
      </ul>
    </div>
    <div class="container-1">
      <span class="icon"><i class="fa fa-search"></i></span>
      <input type="search" id="search" placeholder="Search..." />
    </div>
  </div>
</div>