多選與單選（Checks & radios）
使用我們重構(gòu)過的勾選組件，建立跨瀏覽器、跨設(shè)備皆一致的復(fù)選框（checkbox）及單選按鈕（radio）。
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方法
瀏覽器默認(rèn)的復(fù)選框和單選按鈕被.form-check所取代，這是一系列用于兩種輸入類型的類，它們改進(jìn)了HTML元素的布局和行為，提供了更好的自定義和跨瀏覽器一致性。復(fù)選框用于在列表中選擇一個或多個選項(xiàng)，而單選按鈕用于從多個選項(xiàng)中選擇一個選項(xiàng)。
在結(jié)構(gòu)上，我們的input和label是兄弟元素，而不是label中的input。由于必須指定id和屬性才能將input和label關(guān)聯(lián)起來，因此這會稍微詳細(xì)一些。我們對所有input狀態(tài)使用同級選擇器（~），例如：checked或：disabled。當(dāng)與.form-check-label類結(jié)合使用時，我們可以根據(jù)input的狀態(tài)輕松地為每個項(xiàng)設(shè)置文本樣式。
復(fù)選框
<div class="form-check">
<input class="form-check-input" type="checkbox" value="" id="flexCheckDefault">
<label class="form-check-label" for="flexCheckDefault">
Default checkbox
</label>
</div>
<div class="form-check">
<input class="form-check-input" type="checkbox" value="" id="flexCheckChecked" checked>
<label class="form-check-label" for="flexCheckChecked">
Checked checkbox
</label>
</div>不確定
當(dāng)通過JavaScript手動設(shè)置時，復(fù)選框可以利用不確定偽類 :indeterminate（沒有可用的HTML屬性來指定它）。
<div class="form-check">
<input class="form-check-input" type="checkbox" value="" id="flexCheckIndeterminate">
<label class="form-check-label" for="flexCheckIndeterminate">
Indeterminate checkbox
</label>
</div>禁用
添加disabled屬性，相關(guān)的label將自動設(shè)置為與較淺顏色匹配的樣式，以幫助指示輸入的狀態(tài)。
<div class="form-check">
<input class="form-check-input" type="checkbox" value="" id="flexCheckDisabled" disabled>
<label class="form-check-label" for="flexCheckDisabled">
Disabled checkbox
</label>
</div>
<div class="form-check">
<input class="form-check-input" type="checkbox" value="" id="flexCheckCheckedDisabled" checked disabled>
<label class="form-check-label" for="flexCheckCheckedDisabled">
Disabled checked checkbox
</label>
</div>單選按鈕
<div class="form-check">
<input class="form-check-input" type="radio" name="flexRadioDefault" id="flexRadioDefault1">
<label class="form-check-label" for="flexRadioDefault1">
Default radio
</label>
</div>
<div class="form-check">
<input class="form-check-input" type="radio" name="flexRadioDefault" id="flexRadioDefault2" checked>
<label class="form-check-label" for="flexRadioDefault2">
Default checked radio
</label>
</div>禁用
添加disabled屬性，相關(guān)的label將自動設(shè)置為與較淺顏色匹配的樣式，以幫助指示輸入的狀態(tài)。
<div class="form-check">
<input class="form-check-input" type="radio" name="flexRadioDisabled" id="flexRadioDisabled" disabled>
<label class="form-check-label" for="flexRadioDisabled">
Disabled radio
</label>
</div>
<div class="form-check">
<input class="form-check-input" type="radio" name="flexRadioDisabled" id="flexRadioCheckedDisabled" checked disabled>
<label class="form-check-label" for="flexRadioCheckedDisabled">
Disabled checked radio
</label>
</div>開關(guān)
開關(guān)具有自定義復(fù)選框的標(biāo)記，但使用.form-switch類來呈現(xiàn)切換開關(guān)。開關(guān)還支持disabled屬性。
<div class="form-check form-switch">
<input class="form-check-input" type="checkbox" id="flexSwitchCheckDefault">
<label class="form-check-label" for="flexSwitchCheckDefault">Default switch checkbox input</label>
</div>
<div class="form-check form-switch">
<input class="form-check-input" type="checkbox" id="flexSwitchCheckChecked" checked>
<label class="form-check-label" for="flexSwitchCheckChecked">Checked switch checkbox input</label>
</div>
<div class="form-check form-switch">
<input class="form-check-input" type="checkbox" id="flexSwitchCheckDisabled" disabled>
<label class="form-check-label" for="flexSwitchCheckDisabled">Disabled switch checkbox input</label>
</div>
<div class="form-check form-switch">
<input class="form-check-input" type="checkbox" id="flexSwitchCheckCheckedDisabled" checked disabled>
<label class="form-check-label" for="flexSwitchCheckCheckedDisabled">Disabled checked switch checkbox input</label>
</div>默認(rèn) (疊放)
默認(rèn)情況下，任何數(shù)量的直接同級復(fù)選框和單選按鈕都將垂直堆疊，并使用 .form-check適當(dāng)隔開。
<div class="form-check">
<input class="form-check-input" type="checkbox" value="" id="defaultCheck1">
<label class="form-check-label" for="defaultCheck1">
Default checkbox
</label>
</div>
<div class="form-check">
<input class="form-check-input" type="checkbox" value="" id="defaultCheck2" disabled>
<label class="form-check-label" for="defaultCheck2">
Disabled checkbox
</label>
</div><div class="form-check">
<input class="form-check-input" type="radio" name="exampleRadios" id="exampleRadios1" value="option1" checked>
<label class="form-check-label" for="exampleRadios1">
Default radio
</label>
</div>
<div class="form-check">
<input class="form-check-input" type="radio" name="exampleRadios" id="exampleRadios2" value="option2">
<label class="form-check-label" for="exampleRadios2">
Second default radio
</label>
</div>
<div class="form-check">
<input class="form-check-input" type="radio" name="exampleRadios" id="exampleRadios3" value="option3" disabled>
<label class="form-check-label" for="exampleRadios3">
Disabled radio
</label>
</div>內(nèi)聯(lián)
通過將.form-check-inline添加到.form-check，將復(fù)選框或單選框在同一水平行上分組顯示。
<div class="form-check form-check-inline">
<input class="form-check-input" type="checkbox" id="inlineCheckbox1" value="option1">
<label class="form-check-label" for="inlineCheckbox1">1</label>
</div>
<div class="form-check form-check-inline">
<input class="form-check-input" type="checkbox" id="inlineCheckbox2" value="option2">
<label class="form-check-label" for="inlineCheckbox2">2</label>
</div>
<div class="form-check form-check-inline">
<input class="form-check-input" type="checkbox" id="inlineCheckbox3" value="option3" disabled>
<label class="form-check-label" for="inlineCheckbox3">3 (disabled)</label>
</div><div class="form-check form-check-inline">
<input class="form-check-input" type="radio" name="inlineRadioOptions" id="inlineRadio1" value="option1">
<label class="form-check-label" for="inlineRadio1">1</label>
</div>
<div class="form-check form-check-inline">
<input class="form-check-input" type="radio" name="inlineRadioOptions" id="inlineRadio2" value="option2">
<label class="form-check-label" for="inlineRadio2">2</label>
</div>
<div class="form-check form-check-inline">
<input class="form-check-input" type="radio" name="inlineRadioOptions" id="inlineRadio3" value="option3" disabled>
<label class="form-check-label" for="inlineRadio3">3 (disabled)</label>
</div>無標(biāo)簽
對于沒有標(biāo)簽文本的復(fù)選框和收音機(jī)，省略wrapping.form復(fù)選框。記住，仍然要為輔助技術(shù)提供某種形式的可訪問名稱（例如，使用aria-label標(biāo)簽）。有關(guān)詳細(xì)信息，請參見表單概述輔助功能部分。
<div>
<input class="form-check-input" type="checkbox" id="checkboxNoLabel" value="" aria-label="...">
</div>
<div>
<input class="form-check-input" type="radio" name="radioNoLabel" id="radioNoLabel1" value="" aria-label="...">
</div>切換按鈕
通過使用.btn樣式而不是
復(fù)選切換按鈕
<input type="checkbox" class="btn-check" id="btn-check" autocomplete="off">
<label class="btn btn-primary" for="btn-check">Single toggle</label><input type="checkbox" class="btn-check" id="btn-check-2" checked autocomplete="off">
<label class="btn btn-primary" for="btn-check-2">Checked</label><input type="checkbox" class="btn-check" id="btn-check-3" autocomplete="off" disabled>
<label class="btn btn-primary" for="btn-check-3">Disabled</label>
從外觀上看，這些復(fù)選框切換按鈕與按鈕插件切換按鈕相同。然而，輔助技術(shù)傳達(dá)的方式不同：屏幕閱讀器會將復(fù)選框切換宣布為“選中”/“未選中”（因?yàn)橥庥^如此，但它們本質(zhì)上仍然是復(fù)選框），而按鈕插件切換按鈕將宣布為“按鈕”/“按下按鈕”。這兩種方法之間的選擇將取決于您正在創(chuàng)建的切換類型，以及當(dāng)作為復(fù)選框或?qū)嶋H按鈕發(fā)布時，切換對用戶是否有意義。
單選切換按鈕
<input type="radio" class="btn-check" name="options" id="option1" autocomplete="off" checked>
<label class="btn btn-secondary" for="option1">Checked</label>
<input type="radio" class="btn-check" name="options" id="option2" autocomplete="off">
<label class="btn btn-secondary" for="option2">Radio</label>
<input type="radio" class="btn-check" name="options" id="option3" autocomplete="off" disabled>
<label class="btn btn-secondary" for="option3">Disabled</label>
<input type="radio" class="btn-check" name="options" id="option4" autocomplete="off">
<label class="btn btn-secondary" for="option4">Radio</label>輪廓樣式
支持.btn的不同變量，例如各種outline樣式是被支持的。
<input type="checkbox" class="btn-check" id="btn-check-outlined" autocomplete="off">
<label class="btn btn-outline-primary" for="btn-check-outlined">Single toggle</label><br>
<input type="checkbox" class="btn-check" id="btn-check-2-outlined" checked autocomplete="off">
<label class="btn btn-outline-secondary" for="btn-check-2-outlined">Checked</label><br>
<input type="radio" class="btn-check" name="options-outlined" id="success-outlined" autocomplete="off" checked>
<label class="btn btn-outline-success" for="success-outlined">Checked success radio</label>
<input type="radio" class="btn-check" name="options-outlined" id="danger-outlined" autocomplete="off">
<label class="btn btn-outline-danger" for="danger-outlined">Danger radio</label>Sass
Variables
$form-check-input-width: 1em;
$form-check-min-height: $font-size-base * $line-height-base;
$form-check-padding-start: $form-check-input-width + .5em;
$form-check-margin-bottom: .125rem;
$form-check-label-color: null;
$form-check-label-cursor: null;
$form-check-transition: null;
$form-check-input-active-filter: brightness(90%);
$form-check-input-bg: $input-bg;
$form-check-input-border: 1px solid rgba(0, 0, 0, .25);
$form-check-input-border-radius: .25em;
$form-check-radio-border-radius: 50%;
$form-check-input-focus-border: $input-focus-border-color;
$form-check-input-focus-box-shadow: $input-btn-focus-box-shadow;
$form-check-input-checked-color: $component-active-color;
$form-check-input-checked-bg-color: $component-active-bg;
$form-check-input-checked-border-color: $form-check-input-checked-bg-color;
$form-check-input-checked-bg-image: url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 20'><path fill='none' stroke='#{$form-check-input-checked-color}' stroke-linecap='round' stroke-linejoin='round' stroke-width='3' d='M6 10l3 3l6-6'/></svg>");
$form-check-radio-checked-bg-image: url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='-4 -4 8 8'><circle r='2' fill='#{$form-check-input-checked-color}'/></svg>");
$form-check-input-indeterminate-color: $component-active-color;
$form-check-input-indeterminate-bg-color: $component-active-bg;
$form-check-input-indeterminate-border-color: $form-check-input-indeterminate-bg-color;
$form-check-input-indeterminate-bg-image: url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 20'><path fill='none' stroke='#{$form-check-input-indeterminate-color}' stroke-linecap='round' stroke-linejoin='round' stroke-width='3' d='M6 10h8'/></svg>");
$form-check-input-disabled-opacity: .5;
$form-check-label-disabled-opacity: $form-check-input-disabled-opacity;
$form-check-btn-check-disabled-opacity: $btn-disabled-opacity;
$form-check-inline-margin-end: 1rem;