创建漂浮在输入字段上的精美简单的表单标签。
例
将一对 and 元素包装在其中，以启用带有 Bootstrap 的文本表单字段的浮动标签。<input class="form-control"><label>.form-floating
每个都需要一个非空属性，因为我们的仅 CSS 浮动标签实现依赖于伪元素来检测输入何时为空。占位符文本本身不可见;仅向用户显示 。placeholder<input>:placeholder-shown<label>
另请注意，必须排在第一位，以便我们可以使用同级选择器（即 ）。<input>~
<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>当已经定义时，s 将自动调整到其浮动位置。value<label>
<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>表单验证样式也按预期工作。
<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>文本区域
默认情况下，s with 将与 s 高度相同。<textarea>.form-control<input>
<div class="form-floating">
<textarea class="form-control" placeholder="Leave a comment here" id="floatingTextarea"></textarea>
<label for="floatingTextarea">Comments</label>
</div>要在 上设置自定义高度，请不要使用该属性。相反，请设置显式（内联或通过自定义 CSS）。<textarea>rowsheight
<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 之外，浮动标签仅在 s 上可用。它们的工作方式相同，但与 s 不同的是，它们将始终显示浮动状态。不支持具有大小和倍数的选择。.form-control.form-select<input><label>
<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布尔属性，使其外观灰显，删除指针事件，并防止聚焦。disabled
<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>只读纯文本
浮动标签还支持 ，这有助于在不影响页面布局的情况下从可编辑值切换到纯文本值。.form-control-plaintext<input>
<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>输入组
浮动标签还支持 ..input-group
@
<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>当使用 和 与表单验证一起使用时，应将 放置在 的外部，但放置在 的内部。这意味着需要使用 javascript 显示反馈。.input-group.form-floating-feedback.form-floating.input-group
@
请选择一个用户名。
<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。
<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系统
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;