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创建美观且简单的表单标签,使其悬浮在输入字段上方。

示例

将一对 <input class="form-control"><label> 元素包装在 .form-floating 中,以使用 Bootstrap 的文本表单字段启用浮动标签。每个 <input> 上都需要一个 placeholder,因为我们的 CSS 专用浮动标签方法使用 :placeholder-shown 伪元素。另请注意,<input> 必须排在前面,以便我们可以使用同级选择器(例如,~)。

html
<div class="form-floating mb-3">
  <input type="email" class="form-control" id="floatingInput" placeholder="[email protected]">
  <label for="floatingInput">Email address</label>
</div>
<div class="form-floating">
  <input type="password" class="form-control" id="floatingPassword" placeholder="Password">
  <label for="floatingPassword">Password</label>
</div>

当已经定义了 value 时,<label> 会自动调整到其浮动位置。

html
<form class="form-floating">
  <input type="email" class="form-control" id="floatingInputValue" placeholder="[email protected]" value="[email protected]">
  <label for="floatingInputValue">Input with value</label>
</form>

表单验证样式也能按预期工作。

html
<form class="form-floating">
  <input type="email" class="form-control is-invalid" id="floatingInputInvalid" placeholder="[email protected]" value="[email protected]">
  <label for="floatingInputInvalid">Invalid input</label>
</form>

文本区域

默认情况下,带有 .form-control<textarea><input> 的高度相同。

html
<div class="form-floating">
  <textarea class="form-control" placeholder="Leave a comment here" id="floatingTextarea"></textarea>
  <label for="floatingTextarea">Comments</label>
</div>

要为 <textarea> 设置自定义高度,请不要使用 rows 属性。相反,设置一个明确的 height(内联或通过自定义 CSS)。

html
<div class="form-floating">
  <textarea class="form-control" placeholder="Leave a comment here" id="floatingTextarea2" style="height: 100px"></textarea>
  <label for="floatingTextarea2">Comments</label>
</div>

选择

除了 .form-control 之外,浮动标签仅适用于 .form-select。它们的工作方式相同,但与 <input> 不同,它们始终会以浮动状态显示 <label>不支持具有 sizemultiple 的选择。

html
<div class="form-floating">
  <select class="form-select" id="floatingSelect" aria-label="Floating label select example">
    <option selected>Open this select menu</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
  </select>
  <label for="floatingSelect">Works with selects</label>
</div>

禁用

在输入、文本区域或选择上添加 disabled 布尔属性,使其呈现灰色外观,移除指针事件并防止聚焦。

html
<div class="form-floating mb-3">
  <input type="email" class="form-control" id="floatingInputDisabled" placeholder="[email protected]" disabled>
  <label for="floatingInputDisabled">Email address</label>
</div>
<div class="form-floating mb-3">
  <textarea class="form-control" placeholder="Leave a comment here" id="floatingTextareaDisabled" disabled></textarea>
  <label for="floatingTextareaDisabled">Comments</label>
</div>
<div class="form-floating mb-3">
  <textarea class="form-control" placeholder="Leave a comment here" id="floatingTextarea2Disabled" style="height: 100px" disabled>Disabled textarea with some text inside</textarea>
  <label for="floatingTextarea2Disabled">Comments</label>
</div>
<div class="form-floating">
  <select class="form-select" id="floatingSelectDisabled" aria-label="Floating label disabled select example" disabled>
    <option selected>Open this select menu</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
  </select>
  <label for="floatingSelectDisabled">Works with selects</label>
</div>

只读纯文本

浮动标签还支持 .form-control-plaintext,这对于在可编辑 <input> 和纯文本值之间切换而不会影响页面布局非常有用。

html
<div class="form-floating mb-3">
  <input type="email" readonly class="form-control-plaintext" id="floatingEmptyPlaintextInput" placeholder="[email protected]">
  <label for="floatingEmptyPlaintextInput">Empty input</label>
</div>
<div class="form-floating mb-3">
  <input type="email" readonly class="form-control-plaintext" id="floatingPlaintextInput" placeholder="[email protected]" value="[email protected]">
  <label for="floatingPlaintextInput">Input with value</label>
</div>

输入组

浮动标签还支持 .input-group

@
html
<div class="input-group mb-3">
  <span class="input-group-text">@</span>
  <div class="form-floating">
    <input type="text" class="form-control" id="floatingInputGroup1" placeholder="Username">
    <label for="floatingInputGroup1">Username</label>
  </div>
</div>

在使用 .input-group.form-floating 以及表单验证时,-feedback 应放置在 .form-floating 之外,但放在 .input-group 之内。这意味着需要使用 JavaScript 显示反馈。

@
请选择一个用户名。
html
<div class="input-group has-validation">
  <span class="input-group-text">@</span>
  <div class="form-floating is-invalid">
    <input type="text" class="form-control is-invalid" id="floatingInputGroup2" placeholder="Username" required>
    <label for="floatingInputGroup2">Username</label>
  </div>
  <div class="invalid-feedback">
    Please choose a username.
  </div>
</div>

布局

使用 Bootstrap 网格系统时,请务必将表单元素放置在列类中。

html
<div class="row g-2">
  <div class="col-md">
    <div class="form-floating">
      <input type="email" class="form-control" id="floatingInputGrid" placeholder="[email protected]" value="[email protected]">
      <label for="floatingInputGrid">Email address</label>
    </div>
  </div>
  <div class="col-md">
    <div class="form-floating">
      <select class="form-select" id="floatingSelectGrid">
        <option selected>Open this select menu</option>
        <option value="1">One</option>
        <option value="2">Two</option>
        <option value="3">Three</option>
      </select>
      <label for="floatingSelectGrid">Works with selects</label>
    </div>
  </div>
</div>

CSS

Sass 变量

$form-floating-height:                  add(3.5rem, $input-height-border);
$form-floating-line-height:             1.25;
$form-floating-padding-x:               $input-padding-x;
$form-floating-padding-y:               1rem;
$form-floating-input-padding-t:         1.625rem;
$form-floating-input-padding-b:         .625rem;
$form-floating-label-height:            1.5em;
$form-floating-label-opacity:           .65;
$form-floating-label-transform:         scale(.85) translateY(-.5rem) translateX(.15rem);
$form-floating-label-disabled-color:    $gray-600;
$form-floating-transition:              opacity .1s ease-in-out, transform .1s ease-in-out;