学习 Bootstrap 打通任督二脉（五）

本文旨在根据官方文档全面学习 Bootstrap. 学习其目标在于为之后使用其他更加高级的组件库打下坚实的基础。同时由于 Bootstrap 在移动端的亮眼表现，到目前为止，已经是不可逾越的技术点，因此在本文中，让我们下定决心一起突破，拿下 Bootstrap, 打通任督二脉。

卡片

使用 card-* 组类名实现卡片样式。如下所示的基本效果。

大图+标题+描述+底部按钮

<div class="card" style="width: 18rem;">
  <img src="..." class="card-img-top" alt="...">
  <div class="card-body">
    <h5 class="card-title">Card title</h5>
    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
    <a href="#" class="btn btn-primary">Go somewhere</a>
  </div>
</div>

• class="card": 容器加此类名
• class="card-img-top": 因为图片在上面，所以是 -top
• h5 class="card-title": 内容标题的元素和类名
• p class="card-text": 内容本身的元素和类名
• class="btn btn-primary": 底部按钮

副标题+超链接

<div class="card" style="width: 18rem;">
  <div class="card-body">
    <h5 class="card-title">Card title</h5>
    <h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
    <a href="#" class="card-link">Card link</a>
    <a href="#" class="card-link">Another link</a>
  </div>
</div>

• h6 class="card-subtitle": 内容元素和副标题
• a href="#" class="card-link": 卡片中的超链接样式

card 和 list groups

<div class="card" style="width: 18rem;">
  <div class="card-header">
    Featured
  </div>
  <ul class="list-group list-group-flush">
    <li class="list-group-item">An item</li>
    <li class="list-group-item">A second item</li>
    <li class="list-group-item">A third item</li>
  </ul>
  <div class="card-footer">
    Card footer
  </div>
</div>

card 与多个 body

<div class="card" style="width: 18rem;">
  <img src="..." class="card-img-top" alt="...">
  <div class="card-body">
    <h5 class="card-title">Card title</h5>
    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
  </div>
  <ul class="list-group list-group-flush">
    <li class="list-group-item">An item</li>
    <li class="list-group-item">A second item</li>
    <li class="list-group-item">A third item</li>
  </ul>
  <div class="card-body">
    <a href="#" class="card-link">Card link</a>
    <a href="#" class="card-link">Another link</a>
  </div>
</div>

文字居中和居右

<div class="card text-center">
  <div class="card-header">
    Featured
  </div>
  <div class="card-body">
    <h5 class="card-title">Special title treatment</h5>
    <p class="card-text">With supporting text below as a natural lead-in to additional content.</p>
    <a href="#" class="btn btn-primary">Go somewhere</a>
  </div>
  <div class="card-footer text-muted">
    2 days ago
  </div>
</div>

<div class="card text-end" style="width: 18rem;">
  <div class="card-body">
    <h5 class="card-title">Special title treatment</h5>
    <p class="card-text">With supporting text below as a natural lead-in to additional content.</p>
    <a href="#" class="btn btn-primary">Go somewhere</a>
  </div>
</div>

card 和 nav

使用 card 和 nav 能够实现如下的效果：

<div class="card text-center">
  <div class="card-header">
    <ul class="nav nav-tabs card-header-tabs">
      <li class="nav-item">
        <a class="nav-link active" aria-current="true" href="#">Active</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Link</a>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled">Disabled</a>
      </li>
    </ul>
  </div>
  <div class="card-body">
    <h5 class="card-title">Special title treatment</h5>
    <p class="card-text">With supporting text below as a natural lead-in to additional content.</p>
    <a href="#" class="btn btn-primary">Go somewhere</a>
  </div>
</div>

使用 nav nav-pills card-header-pills 替换 nav nav-tabs card-header-tabs

<div class="card text-center">
  <div class="card-header">
    <ul class="nav nav-pills card-header-pills">
      <li class="nav-item">
        <a class="nav-link active" href="#">Active</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Link</a>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled">Disabled</a>
      </li>
    </ul>
  </div>
  <div class="card-body">
    <h5 class="card-title">Special title treatment</h5>
    <p class="card-text">With supporting text below as a natural lead-in to additional content.</p>
    <a href="#" class="btn btn-primary">Go somewhere</a>
  </div>
</div>

卡片的背景图

使用 card-img 实现背景图片的样式。

<div class="card bg-dark text-white">
  <img src="..." class="card-img" alt="...">
  <div class="card-img-overlay">
    <h5 class="card-title">Card title</h5>
    <p class="card-text">This is a wider card with supporting text below as a natural lead-in to additional content. This content is a little bit longer.</p>
    <p class="card-text">Last updated 3 mins ago</p>
  </div>
</div>

结合 layout 实现左图右文的效果

<div class="card mb-3" style="max-width: 540px;">
  <div class="row g-0">
    <div class="col-md-4">
      <img src="..." class="img-fluid rounded-start" alt="...">
    </div>
    <div class="col-md-8">
      <div class="card-body">
        <h5 class="card-title">Card title</h5>
        <p class="card-text">This is a wider card with supporting text below as a natural lead-in to additional content. This content is a little bit longer.</p>
        <p class="card-text"><small class="text-muted">Last updated 3 mins ago</small></p>
      </div>
    </div>
  </div>
</div>

卡片文字样式和背景色

<div class="card text-white bg-primary mb-3" style="max-width: 18rem;">

给卡片设置边框

使用 border-* 给卡片设置边框：

<div class="card border-primary mb-3" style="max-width: 18rem;">

card-group

使用 card-group 可以将多个卡片组合起来，其原理为：

.card-group {
  // The child selector allows nested `.card` within `.card-group`
  // to display properly.
  > .card {
    margin-bottom: $card-group-margin;
  }

  @include media-breakpoint-up(sm) {
    display: flex;
    flex-flow: row wrap;
    // The child selector allows nested `.card` within `.card-group`
    // to display properly.
    > .card {
      // Flexbugs #4: https://github.com/philipwalton/flexbugs#flexbug-4
      flex: 1 0 0%;
      margin-bottom: 0;

      + .card {
        margin-left: 0;
        border-left: 0;
      }

      // Handle rounded corners
      @if $enable-rounded {
        &:not(:last-child) {
          @include border-end-radius(0);

          .card-img-top,
          .card-header {
            // stylelint-disable-next-line property-disallowed-list
            border-top-right-radius: 0;
          }
          .card-img-bottom,
          .card-footer {
            // stylelint-disable-next-line property-disallowed-list
            border-bottom-right-radius: 0;
          }
        }

        &:not(:first-child) {
          @include border-start-radius(0);

          .card-img-top,
          .card-header {
            // stylelint-disable-next-line property-disallowed-list
            border-top-left-radius: 0;
          }
          .card-img-bottom,
          .card-footer {
            // stylelint-disable-next-line property-disallowed-list
            border-bottom-left-radius: 0;
          }
        }
      }
    }
  }
}

轮播图

轮播图的原理：The carousel is a slideshow for cycling through a series of content, built with CSS 3D transforms and a bit of JavaScript. It works with a series of images, text, or custom markup. It also includes support for previous/next controls and indicators.

最简单的轮播图

<div id="carouselExampleSlidesOnly" class="carousel slide" data-bs-ride="carousel">
  <div class="carousel-inner">
    <div class="carousel-item active">
      <img src="..." class="d-block w-100" alt="...">
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
    </div>
  </div>
</div>

• id="carouselExampleSlidesOnly": 这个是内部元素用来引用轮播图的 handle
• class="carousel slide" data-bs-ride="carousel": 用来放在轮播图的外层容器中
• class="carousel-inner" 包裹轮播图 item 的次外层组件
• class="carousel-item active" 当前被激活的次外层组件

带向前向后翻页的轮播图组件

<div id="carouselExampleControls" class="carousel slide" data-bs-ride="carousel">
  <div class="carousel-inner">
    <div class="carousel-item active">
      <img src="..." class="d-block w-100" alt="...">
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
    </div>
  </div>
  <button class="carousel-control-prev" type="button" data-bs-target="#carouselExampleControls" data-bs-slide="prev">
    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
    <span class="visually-hidden">Previous</span>
  </button>
  <button class="carousel-control-next" type="button" data-bs-target="#carouselExampleControls" data-bs-slide="next">
    <span class="carousel-control-next-icon" aria-hidden="true"></span>
    <span class="visually-hidden">Next</span>
  </button>
</div>

• button: 注意 button 的位置是在所有 carousel-item 之后
• class="carousel-control-prev carousel-control-next": 向前翻页和向后翻页组件的类名
• data-bs-target="#carouselExampleControls": 表明对哪个轮播图生效
• data-bs-slide="prev" data-bs-slide="next": 表明组件的作用是向前还是向后翻页

带指示组件的轮播图

<div id="carouselExampleIndicators" class="carousel slide" data-bs-ride="carousel">
  <div class="carousel-indicators">
    <button type="button" data-bs-target="#carouselExampleIndicators" data-bs-slide-to="0" class="active" aria-current="true" aria-label="Slide 1"></button>
    <button type="button" data-bs-target="#carouselExampleIndicators" data-bs-slide-to="1" aria-label="Slide 2"></button>
    <button type="button" data-bs-target="#carouselExampleIndicators" data-bs-slide-to="2" aria-label="Slide 3"></button>
  </div>
  <div class="carousel-inner">
    <div class="carousel-item active">
      <img src="..." class="d-block w-100" alt="...">
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
    </div>
  </div>
  <button class="carousel-control-prev" type="button" data-bs-target="#carouselExampleIndicators" data-bs-slide="prev">
    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
    <span class="visually-hidden">Previous</span>
  </button>
  <button class="carousel-control-next" type="button" data-bs-target="#carouselExampleIndicators" data-bs-slide="next">
    <span class="carousel-control-next-icon" aria-hidden="true"></span>
    <span class="visually-hidden">Next</span>
  </button>
</div>

指示组件指的是：

  <div class="carousel-indicators">
    <button type="button" data-bs-target="#carouselExampleIndicators" data-bs-slide-to="0" class="active" aria-current="true" aria-label="Slide 1"></button>
    <button type="button" data-bs-target="#carouselExampleIndicators" data-bs-slide-to="1" aria-label="Slide 2"></button>
    <button type="button" data-bs-target="#carouselExampleIndicators" data-bs-slide-to="2" aria-label="Slide 3"></button>
  </div>

• 注意指示器组件的位置
• class="carousel-indicators": 指示功能的外层组件
• data-bs-target="#carouselExampleIndicators": 表明指示器对那个轮播图生效
• ata-bs-slide-to="0": 指示器的序列号
• class="active": 当前是否被激活

带标题的轮播图

<div id="carouselExampleCaptions" class="carousel slide" data-bs-ride="carousel">
  <div class="carousel-indicators">
    <button type="button" data-bs-target="#carouselExampleCaptions" data-bs-slide-to="0" class="active" aria-current="true" aria-label="Slide 1"></button>
    <button type="button" data-bs-target="#carouselExampleCaptions" data-bs-slide-to="1" aria-label="Slide 2"></button>
    <button type="button" data-bs-target="#carouselExampleCaptions" data-bs-slide-to="2" aria-label="Slide 3"></button>
  </div>
  <div class="carousel-inner">
    <div class="carousel-item active">
      <img src="..." class="d-block w-100" alt="...">
      <div class="carousel-caption d-none d-md-block">
        <h5>First slide label</h5>
        <p>Some representative placeholder content for the first slide.</p>
      </div>
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
      <div class="carousel-caption d-none d-md-block">
        <h5>Second slide label</h5>
        <p>Some representative placeholder content for the second slide.</p>
      </div>
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
      <div class="carousel-caption d-none d-md-block">
        <h5>Third slide label</h5>
        <p>Some representative placeholder content for the third slide.</p>
      </div>
    </div>
  </div>
  <button class="carousel-control-prev" type="button" data-bs-target="#carouselExampleCaptions" data-bs-slide="prev">
    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
    <span class="visually-hidden">Previous</span>
  </button>
  <button class="carousel-control-next" type="button" data-bs-target="#carouselExampleCaptions" data-bs-slide="next">
    <span class="carousel-control-next-icon" aria-hidden="true"></span>
    <span class="visually-hidden">Next</span>
  </button>
</div>

其中：

      <div class="carousel-caption d-none d-md-block">
        <h5>First slide label</h5>
        <p>Some representative placeholder content for the first slide.</p>
      </div>

为添加的 caption: 所谓 caption 指的是在小屏下消失但是大屏下会展示出来d-none d-md-block带有一定样式carousel-caption的文字。

渐变替换而不是滑动替换

在最外层组件上，使用 carousel slide carousel-fade 代替 carousel slide 就可以渐变切换而不是滑动切换。

指定切换时间

在每一个 div.carousel-item 上添加名为 data-bs-interval="10000" 的属性就可以指定在此 slide 上停留的时间有多久。如下所示：

<div id="carouselExampleInterval" class="carousel slide" data-bs-ride="carousel">
  <div class="carousel-inner">
    <div class="carousel-item active" data-bs-interval="10000">
      <img src="..." class="d-block w-100" alt="...">
    </div>
    <div class="carousel-item" data-bs-interval="2000">
      <img src="..." class="d-block w-100" alt="...">
    </div>
    <div class="carousel-item">
      <img src="..." class="d-block w-100" alt="...">
    </div>
  </div>
  <button class="carousel-control-prev" type="button" data-bs-target="#carouselExampleInterval" data-bs-slide="prev">
    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
    <span class="visually-hidden">Previous</span>
  </button>
  <button class="carousel-control-next" type="button" data-bs-target="#carouselExampleInterval" data-bs-slide="next">
    <span class="carousel-control-next-icon" aria-hidden="true"></span>
    <span class="visually-hidden">Next</span>
  </button>
</div>

其他

1. 在最外层组件使用 data-bs-touch="false" 禁止触屏滑动切换。
2. 在最外层组件使用 data-bs-interval="false" 并且去除 data-bs-ride="carousel" 的方式禁止自动播放。

关闭按钮

基本样式

<button type="button" class="btn-close" aria-label="Close"></button>

禁用按钮

<button type="button" class="btn-close" disabled aria-label="Close"></button>

暗色模式

<button type="button" class="btn-close btn-close-white" aria-label="Close"></button>
<button type="button" class="btn-close btn-close-white" disabled aria-label="Close"></button>

下拉菜单

最基本的下拉菜单

<div class="dropdown">
  <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton1" data-bs-toggle="dropdown" aria-expanded="false">
    Dropdown button
  </button>
  <ul class="dropdown-menu" aria-labelledby="dropdownMenuButton1">
    <li><a class="dropdown-item" href="#">Action</a></li>
    <li><a class="dropdown-item" href="#">Another action</a></li>
    <li><a class="dropdown-item" href="#">Something else here</a></li>
  </ul>
</div>

• dropdown: 表示的就是最外层元素的类名
• button class="btn btn-secondary dropdown-toggle": dropdown-toggle 表示它可以控制一个 dropdown，所以需要添加对应的样式
• id="dropdownMenuButton1": 是展开元素寻找的依据
• data-bs-toggle="dropdown": 这个才是它能控制 dropdown 的原因
• ul.dropdown-menu>(li>a.dropdown-item)*3: 这个是 dropdown 的结构

我们可以将控制按钮从 button 元素换成 a 标签：

<div class="dropdown">
  <a class="btn btn-secondary dropdown-toggle" href="#" role="button" id="dropdownMenuLink" data-bs-toggle="dropdown" aria-expanded="false">
    Dropdown link
  </a>

  <ul class="dropdown-menu" aria-labelledby="dropdownMenuLink">
    <li><a class="dropdown-item" href="#">Action</a></li>
    <li><a class="dropdown-item" href="#">Another action</a></li>
    <li><a class="dropdown-item" href="#">Something else here</a></li>
  </ul>
</div>

我们可以在 dropdown 中添加分割线：

<!-- Example single danger button -->
<div class="btn-group">
  <button type="button" class="btn btn-danger dropdown-toggle" data-bs-toggle="dropdown" aria-expanded="false">
    Action
  </button>
  <ul class="dropdown-menu">
    <li><a class="dropdown-item" href="#">Action</a></li>
    <li><a class="dropdown-item" href="#">Another action</a></li>
    <li><a class="dropdown-item" href="#">Something else here</a></li>
    <li><hr class="dropdown-divider"></li>
    <li><a class="dropdown-item" href="#">Separated link</a></li>
  </ul>
</div>

文字是文字，按钮是按钮

其实文字和按钮都是按钮，只不过分工不同，这个时候需要用到 btn-group.

<!-- Example split danger button -->
<div class="btn-group">
  <button type="button" class="btn btn-danger">Action</button>
  <button type="button" class="btn btn-danger dropdown-toggle dropdown-toggle-split" data-bs-toggle="dropdown" aria-expanded="false">
    <span class="visually-hidden">Toggle Dropdown</span>
  </button>
  <ul class="dropdown-menu">
    <li><a class="dropdown-item" href="#">Action</a></li>
    <li><a class="dropdown-item" href="#">Another action</a></li>
    <li><a class="dropdown-item" href="#">Something else here</a></li>
    <li><hr class="dropdown-divider"></li>
    <li><a class="dropdown-item" href="#">Separated link</a></li>
  </ul>
</div>

btn-group 才是最外层的组件！

dropdown 文字大小

需要给 btn-group 中的每个 button 都添加 btn-lg 等类名，才能完全改变 dropdown 的大小。

dropdown 暗色模式

给 dropdown-menu 添加 dropdown-menu-dark 就可以将背景切换至暗黑，同时文字颜色也变成浅色。

<ul class="dropdown-menu dropdown-menu-dark" aria-labelledby="dropdownMenuButton2">

dropdown 首选项

给 li>a 的 a 或者给 dropdown-item 上添加 active 类名即可选定首选项。

dropup

<!-- Default dropup button -->
<div class="btn-group dropup">
  <button type="button" class="btn btn-secondary dropdown-toggle" data-bs-toggle="dropdown" aria-expanded="false">
    Dropup
  </button>
  <ul class="dropdown-menu">
    <!-- Dropdown menu links -->
  </ul>
</div>

<!-- Split dropup button -->
<div class="btn-group dropup">
  <button type="button" class="btn btn-secondary">
    Split dropup
  </button>
  <button type="button" class="btn btn-secondary dropdown-toggle dropdown-toggle-split" data-bs-toggle="dropdown" aria-expanded="false">
    <span class="visually-hidden">Toggle Dropdown</span>
  </button>
  <ul class="dropdown-menu">
    <!-- Dropdown menu links -->
  </ul>
</div>

dropend

<!-- Default dropend button -->
<div class="btn-group dropend">
  <button type="button" class="btn btn-secondary dropdown-toggle" data-bs-toggle="dropdown" aria-expanded="false">
    Dropright
  </button>
  <ul class="dropdown-menu">
    <!-- Dropdown menu links -->
  </ul>
</div>

<!-- Split dropend button -->
<div class="btn-group dropend">
  <button type="button" class="btn btn-secondary">
    Split dropend
  </button>
  <button type="button" class="btn btn-secondary dropdown-toggle dropdown-toggle-split" data-bs-toggle="dropdown" aria-expanded="false">
    <span class="visually-hidden">Toggle Dropright</span>
  </button>
  <ul class="dropdown-menu">
    <!-- Dropdown menu links -->
  </ul>
</div>

dropleft

<!-- Default dropstart button -->
<div class="btn-group dropstart">
  <button type="button" class="btn btn-secondary dropdown-toggle" data-bs-toggle="dropdown" aria-expanded="false">
    Dropstart
  </button>
  <ul class="dropdown-menu">
    <!-- Dropdown menu links -->
  </ul>
</div>

<!-- Split dropstart button -->
<div class="btn-group">
  <div class="btn-group dropstart" role="group">
    <button type="button" class="btn btn-secondary dropdown-toggle dropdown-toggle-split" data-bs-toggle="dropdown" aria-expanded="false">
      <span class="visually-hidden">Toggle Dropstart</span>
    </button>
    <ul class="dropdown-menu">
      <!-- Dropdown menu links -->
    </ul>
  </div>
  <button type="button" class="btn btn-secondary">
    Split dropstart
  </button>
</div>

将 dropdown-item 的宿主元素换成 button

<div class="dropdown">
  <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenu2" data-bs-toggle="dropdown" aria-expanded="false">
    Dropdown
  </button>
  <ul class="dropdown-menu" aria-labelledby="dropdownMenu2">
    <li><button class="dropdown-item" type="button">Action</button></li>
    <li><button class="dropdown-item" type="button">Another action</button></li>
    <li><button class="dropdown-item" type="button">Something else here</button></li>
  </ul>
</div>

不让选 .disabled

<ul class="dropdown-menu">
  <li><a class="dropdown-item" href="#">Regular link</a></li>
  <li><a class="dropdown-item disabled">Disabled link</a></li>
  <li><a class="dropdown-item" href="#">Another link</a></li>
</ul>

使用 dropdown-menu-end 等改变下拉菜单的对齐方式

<div class="btn-group">
  <button type="button" class="btn btn-secondary dropdown-toggle" data-bs-toggle="dropdown" aria-expanded="false">
    Right-aligned menu example
  </button>
  <ul class="dropdown-menu dropdown-menu-end">
    <li><button class="dropdown-item" type="button">Action</button></li>
    <li><button class="dropdown-item" type="button">Another action</button></li>
    <li><button class="dropdown-item" type="button">Something else here</button></li>
  </ul>
</div>

大屏靠左，小屏靠右

<div class="btn-group">
  <button type="button" class="btn btn-secondary dropdown-toggle" data-bs-toggle="dropdown" data-bs-display="static" aria-expanded="false">
    Right-aligned but left aligned when large screen
  </button>
  <ul class="dropdown-menu dropdown-menu-end dropdown-menu-lg-start">
    <li><button class="dropdown-item" type="button">Action</button></li>
    <li><button class="dropdown-item" type="button">Another action</button></li>
    <li><button class="dropdown-item" type="button">Something else here</button></li>
  </ul>
</div>