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HTML下拉框导致HTML元素向下移动

htmlcssdrop-down-menuz-indexdropdown
3

我想让下拉菜单在展开时覆盖下面的元素。不幸的是，即使处于相同叠加上下文的元素具有位置，并且下拉容器div设置为z-index 2，问题仍然存在；它不是覆盖下面的元素，而是将它们向下移动。 我还尝试通过向各种元素添加不透明度属性来改变叠加上下文，但这也没有起作用。 代码如下：

#firstone {
  z-index: 2;
}

#contain {
  height: 400px;
  width: 400px;
  background-color: rgba(100, 25, 25, 0.2);
}

body {
  text-align: center;
}

input:focus {
  outline: none;
}

.fancy_input_box {
  text-align: left;
  display: inline-block;
  margin: 40px 3% 1px;
  position: relative;
}

.fancy_input {
  font: 15px/24px "Lato", Arial, sans-serif;
  color: #aaa;
  box-sizing: border-box;
  letter-spacing: 1px;
  border: 0;
  padding: 7px 7px;
  border: 1px solid #ccc;
  position: relative;
  background: transparent;
}

.fancy_input:focus~.dropdown-content {
  display: block;
  cursor: default;
}

.fancy_input:focus~.dropdown-content>span {
  display: block;
  cursor: default;
}

.dropdown-content {
  display: none;
  background-color: rgba(0, 0, 0, 0.2);
  width: 222px;
  overflow: auto;
  position: relative;
}

.dropdown-content:active {
  display: block;
}

.dropdown-content>span {
  padding: 12px 16px;
  display: none;
}

.dropdown-content>span:hover {
  background-color: rgba(0, 0, 0, 0.1);
}

.fancy_input~.fancy_label {
  position: absolute;
  left: 14px;
  width: 100%;
  top: 10px;
  color: #aaa;
  letter-spacing: 0.5px;
  transition: 0.3s;
  -webkit-transition: 0.3s;
  -moz-transition: 0.3s;
  z-index: -1;
}

.fancy_input:focus~.fancy_label {
  top: -18px;
  left: 1px;
  font-size: 12px;
  color: grey !important;
  transition: 0.3s;
  -webkit-transition: 0.3s;
  -moz-transition: 0.3s;
}

.fancy_input:focus {
  border: 1px solid grey !important;
}

.fancy_input:not(focus):valid~.fancy_label {
  top: -18px;
  font-size: 12px;
  left: 1px;
  color: #aaa;
  transition: 0.3s;
  -webkit-transition: 0.3s;
  -moz-transition: 0.3s;
}
<!DOCTYPE html>
<html lang="en">

<head>
  <link rel="stylesheet" href="test.css">
</head>

<body>
  <div id="contain">

    <div id="firstone" class="fancy_input_box">
      <input class="fancy_input" type="text" placeholder="" maxlength="25" size="25" required>
      <label class="fancy_label">Search</label>

      <div class="dropdown-content">
        <span>a</span>
        <span>b</span>
        <span>c</span>
        <span>d</span>
        <span>e</span>
      </div>
    </div>

    <div class="fancy_input_box">
      <input class="fancy_input" type="text" placeholder="" maxlength="4" size="10">
      <label class="fancy_label">Thing</label>
    </div>

    <br>

    <div>
      <div class="fancy_input_box">
        <input class="fancy_input" type="text" placeholder="" maxlength="4" size="10">
        <label class="fancy_label">stuff</label>
      </div>

      <div class="fancy_input_box">
        <input class="fancy_input" type="text" placeholder="" maxlength="4" size="10">
        <label class="fancy_label">more stuff</label>
      </div>

      <div class="fancy_input_box">
        <input class="fancy_input" type="text" placeholder="" maxlength="4" size="10">
        <label class="fancy_label">more stuff</label>
      </div>
    </div>

  </div>
</body>

</html>

将 z-index 添加到 .dropdown-content，并将 position 属性更改为 absolute。 - Dev Matee
3个回答
3
你的下拉内容应该采用绝对定位。
更新你的下拉样式如下所示：
.dropdown-content {
  display: none;
  background-color: rgba(0, 0, 0, 0.2);
  width: 222px;
  overflow: auto;
  position: absolute;
  left: 0;
  top: 100%;
}
1
尝试使用绝对定位来设置以下代码。此外，我在下拉内容div中将宽度改为100％以获得良好的设计。 

#firstone {
  z-index: 2;
}

#contain {
  height: 400px;
  width: 400px;
  background-color: rgba(100, 25, 25, 0.2);
}

body {
  text-align: center;
}

input:focus {
  outline: none;
}

.fancy_input_box {
  text-align: left;
  display: inline-block;
  margin: 40px 3% 1px;
  position: relative;
}

.fancy_input {
  font: 15px/24px "Lato", Arial, sans-serif;
  color: #aaa;
  box-sizing: border-box;
  letter-spacing: 1px;
  border: 0;
  padding: 7px 7px;
  border: 1px solid #ccc;
  position: relative;
  background: transparent;
}

.fancy_input:focus~.dropdown-content {
  display: block;
  cursor: default;
}

.fancy_input:focus~.dropdown-content>span {
  display: block;
  cursor: default;
}

.dropdown-content {
  display: none;
  background-color: rgba(0, 0, 0, 0.2);
  width: 100%;
  overflow: auto;
  position: absolute;
  
}

.dropdown-content:active {
  display: block;
}

.dropdown-content>span {
  padding: 12px 16px;
  display: none;
}

.dropdown-content>span:hover {
  background-color: rgba(0, 0, 0, 0.1);
}

.fancy_input~.fancy_label {
  position: absolute;
  left: 14px;
  width: 100%;
  top: 10px;
  color: #aaa;
  letter-spacing: 0.5px;
  transition: 0.3s;
  -webkit-transition: 0.3s;
  -moz-transition: 0.3s;
  z-index: -1;
}

.fancy_input:focus~.fancy_label {
  top: -18px;
  left: 1px;
  font-size: 12px;
  color: grey !important;
  transition: 0.3s;
  -webkit-transition: 0.3s;
  -moz-transition: 0.3s;
}

.fancy_input:focus {
  border: 1px solid grey !important;
}

.fancy_input:not(focus):valid~.fancy_label {
  top: -18px;
  font-size: 12px;
  left: 1px;
  color: #aaa;
  transition: 0.3s;
  -webkit-transition: 0.3s;
  -moz-transition: 0.3s;
}
<div id="contain">

    <div id="firstone" class="fancy_input_box">
      <input class="fancy_input" type="text" placeholder="" maxlength="25" size="25" required>
      <label class="fancy_label">Search</label>

      <div class="dropdown-content">
        <span>a</span>
        <span>b</span>
        <span>c</span>
        <span>d</span>
        <span>e</span>
      </div>
    </div>

    <div class="fancy_input_box">
      <input class="fancy_input" type="text" placeholder="" maxlength="4" size="10">
      <label class="fancy_label">Thing</label>
    </div>

    <br>

    <div>
      <div class="fancy_input_box">
        <input class="fancy_input" type="text" placeholder="" maxlength="4" size="10">
        <label class="fancy_label">stuff</label>
      </div>

      <div class="fancy_input_box">
        <input class="fancy_input" type="text" placeholder="" maxlength="4" size="10">
        <label class="fancy_label">more stuff</label>
      </div>

      <div class="fancy_input_box">
        <input class="fancy_input" type="text" placeholder="" maxlength="4" size="10">
        <label class="fancy_label">more stuff</label>
      </div>
    </div>

  </div>

0

只需在您的下拉内容类中添加position: absolute和top: 100%;

从您的代码中获取jsfiddle

  .dropdown-content {
  display: none;
  background-color: rgba(0, 0, 0, 0.2);
  width: 222px;
  overflow: auto;
  position: absolute;
  left: 0;
  top: 100%;
  }
@robert，请检查这个解决方案。我已经附上了 jsfiddle。 - Ammar Khan
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