浮动标签（Floating labels）

创建精美简洁的表单标签，浮动在输入字段上。

On this page

示例

将一对 <input class=“form-control”> 和 <label> 元素包在 .form-floating 中，以便使用 Bootstrap 的文本表单字段启用浮动标签。每个 <input> 都需要一个 placeholder，因为我们的纯 CSS 浮动标签方法使用了:placeholder-shown 伪元素。还要注意的是，<input> 必须放在前面，这样我们才能使用同级选择器（例如~）。

Email address

Password

html

<div class="form-floating mb-3">
  <input type="email" class="form-control" id="floatingInput" placeholder="name@example.com">
  <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>

如果已经定义了value，<label> 将自动调整到浮动位置。

html

<form class="form-floating">
  <input type="email" class="form-control" id="floatingInputValue" placeholder="name@example.com" value="test@example.com">
  <label for="floatingInputValue">Input with value</label>
</form>

表单验证样式也能正常工作。

html

<form class="form-floating">
  <input type="email" class="form-control is-invalid" id="floatingInputInvalid" placeholder="name@example.com" value="test@example.com">
  <label for="floatingInputInvalid">Invalid input</label>
</form>

文本域

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

Comments

html

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

要在<textarea>上设置自定义高度，请勿使用rows属性。取而代之的是设置明确的 height（内联或通过自定义 CSS）。

Comments

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>

下拉选择

除 .form-control外，浮动标签只适用于 .form-select。它们的工作方式相同，但与 <input> 不同的是，它们将始终以浮动状态显示<label>。不支持带有 size 和 multiple 的选择。

Works with selects

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

在输入框、文本框或选择框上添加 disabled 布尔属性，使其显示为灰色，移除指针事件并防止聚焦。

Email address

Comments

Works with selects

html

<div class="form-floating mb-3">
  <input type="email" class="form-control" id="floatingInputDisabled" placeholder="name@example.com" 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>

纯文本只读

浮动标签还支持 .form-control-plaintext，这有助于在不影响页面布局的情况下从可编辑的 <input> 切换到纯文本值。

Empty input

Input with value

html

<div class="form-floating mb-3">
  <input type="email" readonly class="form-control-plaintext" id="floatingEmptyPlaintextInput" placeholder="name@example.com">
  <label for="floatingEmptyPlaintextInput">Empty input</label>
</div>
<div class="form-floating mb-3">
  <input type="email" readonly class="form-control-plaintext" id="floatingPlaintextInput" placeholder="name@example.com" value="name@example.com">
  <label for="floatingPlaintextInput">Input with value</label>
</div>

输入框组

浮动标签还支持 .input-group。

Username

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 和 .form-floating 以及表单验证时，-feedback 应放在 .form-floating 之外，但应放在 .input-group 之内。这意味着需要使用 javascript 来显示反馈。

Username

Please choose a username.

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，请务必将表单元素置于列类中。

Email address

Works with selects

html

<div class="row g-2">
  <div class="col-md">
    <div class="form-floating">
      <input type="email" class="form-control" id="floatingInputGrid" placeholder="name@example.com" value="mdo@example.com">
      <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

scss/_variables.scss

$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;