学习 Bootstrap 打通任督二脉（二）

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。

Introduction · Bootstrap v5.1 | Bootstrap官方文档中国镜像 (getbootstrap.cn)

边框

设置四个边的边框或者单独设置某一个

<span class="border"></span>
<span class="border-top"></span>
<span class="border-end"></span>
<span class="border-bottom"></span>
<span class="border-start"></span>

设置边的颜色

<span class="border border-primary"></span>
<span class="border border-secondary"></span>
<span class="border border-success"></span>
<span class="border border-danger"></span>
<span class="border border-warning"></span>
<span class="border border-info"></span>
<span class="border border-light"></span>
<span class="border border-dark"></span>
<span class="border border-white"></span>

设置边框的宽度

<span class="border border-1"></span>
<span class="border border-2"></span>
<span class="border border-3"></span>
<span class="border border-4"></span>
<span class="border border-5"></span>

设置默认圆角/设置某个方位圆角

<img src="..." class="rounded" alt="...">
<img src="..." class="rounded-top" alt="...">
<img src="..." class="rounded-end" alt="...">
<img src="..." class="rounded-bottom" alt="...">
<img src="..." class="rounded-start" alt="...">
<img src="..." class="rounded-circle" alt="...">
<img src="..." class="rounded-pill" alt="...">

设置圆角的大小

<img src="..." class="rounded-0" alt="...">
<img src="..." class="rounded-1" alt="...">
<img src="..." class="rounded-2" alt="...">
<img src="..." class="rounded-3" alt="...">

只取消某个边的边框

<span class="border-0"></span>
<span class="border-top-0"></span>
<span class="border-end-0"></span>
<span class="border-bottom-0"></span>
<span class="border-start-0"></span>

颜色

文字颜色

<p class="text-primary">.text-primary</p>
<p class="text-secondary">.text-secondary</p>
<p class="text-success">.text-success</p>
<p class="text-danger">.text-danger</p>
<p class="text-warning bg-dark">.text-warning</p>
<p class="text-info bg-dark">.text-info</p>
<p class="text-light bg-dark">.text-light</p>
<p class="text-dark">.text-dark</p>
<p class="text-body">.text-body</p>
<p class="text-muted">.text-muted</p>
<p class="text-white bg-dark">.text-white</p>
<p class="text-black-50">.text-black-50</p>
<p class="text-white-50 bg-dark">.text-white-50</p>

文字透明度

.text-opacity-50 不是推荐的做法，请使用直接改变透明度的方式。

你可以在 style 中改变 css 变量的值，这样一来就能改变文字的透明度了！

<div class="text-primary" style="--bs-text-opacity: .5;">
    This is 50% opacity primary text
</div>

或者，

.text-primary {
  --bs-text-opacity: 1;
  color: rgba(var(--bs-primary-rgb), var(--bs-text-opacity)) !important;
}

display

先看例子：

<div class="d-inline p-2 bg-primary text-white">d-inline</div>
<div class="d-inline p-2 bg-dark text-white">d-inline</div>

<span class="d-block p-2 bg-primary text-white">d-block</span>
<span class="d-block p-2 bg-dark text-white">d-block</span>

模式是固定的：

.d-{value} for xs

.d-{breakpoint}-{value} for sm, md, lg, xl, and xxl.

Where value is one of:

• none
• inline
• inline-block
• block
• grid
• table
• table-cell
• table-row
• flex
• inline-flex

display 和 break points 的联动

这样做的意义是为了在某些屏幕尺寸下可见或者不可见：

<div class="d-lg-none">hide on lg and wider screens</div>
<div class="d-none d-lg-block">hide on screens smaller than lg</div>

下面的表格是常见情况的汇总：

Screen size	Class
Hidden on all	.d-none
Hidden only on xs	.d-none .d-sm-block
Hidden only on sm	.d-sm-none .d-md-block
Hidden only on md	.d-md-none .d-lg-block
Hidden only on lg	.d-lg-none .d-xl-block
Hidden only on xl	.d-xl-none .d-xxl-block
Hidden only on xxl	.d-xxl-none
Visible on all	.d-block
Visible only on xs	.d-block .d-sm-none
Visible only on sm	.d-none .d-sm-block .d-md-none
Visible only on md	.d-none .d-md-block .d-lg-none
Visible only on lg	.d-none .d-lg-block .d-xl-none
Visible only on xl	.d-none .d-xl-block .d-xxl-none
Visible only on xxl	.d-none .d-xxl-block

屏幕打印的时候不可见

有些内容在使用 ctrl + p 打印的时候并不希望出现，这个时候就可以用 print 族的类名了。

<div class="d-print-none">Screen Only (Hide on print only)</div>
<div class="d-none d-print-block">Print Only (Hide on screen only)</div>
<div class="d-none d-lg-block d-print-block">Hide up to large on screen, but always show on print</div>

除此之外还有：

• .d-print-none
• .d-print-inline
• .d-print-inline-block
• .d-print-block
• .d-print-grid
• .d-print-table
• .d-print-table-row
• .d-print-table-cell
• .d-print-flex
• .d-print-inline-flex

浮动 -- float

1. 左浮动：float-start
2. 右浮动：float-end

3. 清除浮动：clearfix 原理：

浮动和响应式

<div class="float-sm-start">Float start on viewports sized SM (small) or wider</div><br>
<div class="float-md-start">Float start on viewports sized MD (medium) or wider</div><br>
<div class="float-lg-start">Float start on viewports sized LG (large) or wider</div><br>
<div class="float-xl-start">Float start on viewports sized XL (extra-large) or wider</div><br>

• .float-start
• .float-end
• .float-none
• .float-sm-start
• .float-sm-end
• .float-sm-none
• .float-md-start
• .float-md-end
• .float-md-none
• .float-lg-start
• .float-lg-end
• .float-lg-none
• .float-xl-start
• .float-xl-end
• .float-xl-none
• .float-xxl-start
• .float-xxl-end
• .float-xxl-none

用户选择和鼠标事件

user-selection

<p class="user-select-all">This paragraph will be entirely selected when clicked by the user.</p>
<p class="user-select-auto">This paragraph has default select behavior.</p>
<p class="user-select-none">This paragraph will not be selectable when clicked by the user.</p>

point-event

<p><a href="#" class="pe-none" tabindex="-1" aria-disabled="true">This link</a> can not be clicked.</p>
<p><a href="#" class="pe-auto">This link</a> can be clicked (this is default behavior).</p>
<p class="pe-none">
    <a href="#" tabindex="-1" aria-disabled="true">
        This link
    </a> can not be clicked because the <code>pointer-events</code> property is inherited from its parent. However, 
    <a href="#" class="pe-auto">this link</a> has a <code>pe-auto</code> class and can be clicked.
</p>

这里的 tabindex='-1' 的作用是防止键盘选中。

透明度

这其实没啥好说的，记住就行了。

<div class="opacity-100">...</div>
<div class="opacity-75">...</div>
<div class="opacity-50">...</div>
<div class="opacity-25">...</div>

overflow

这其实没啥好说的，记住就行了。

<div class="overflow-auto">...</div>
<div class="overflow-hidden">...</div>
<div class="overflow-visible">...</div>
<div class="overflow-scroll">...</div>

position

将一个 div 完全居中的做法： position-absolute top-50 left-50 translate-middle

快速完成一个 badge 的做法： position-absolute top-0 end-0 translate-middle-y

指定布局方式

<div class="position-static">...</div>
<div class="position-relative">...</div>
<div class="position-absolute">...</div>
<div class="position-fixed">...</div>
<div class="position-sticky">...</div>

子绝父相定位

<div class="position-relative">
  <div class="position-absolute top-0 start-0"></div>
  <div class="position-absolute top-0 end-0"></div>
  <div class="position-absolute top-50 start-50"></div>
  <div class="position-absolute bottom-50 end-50"></div>
  <div class="position-absolute bottom-0 start-0"></div>
  <div class="position-absolute bottom-0 end-0"></div>
</div>

花式居中

<div class="position-relative">
  <div class="position-absolute top-0 start-0 translate-middle"></div>
  <div class="position-absolute top-0 start-50 translate-middle"></div>
  <div class="position-absolute top-0 start-100 translate-middle"></div>
  <div class="position-absolute top-50 start-0 translate-middle"></div>
  <div class="position-absolute top-50 start-50 translate-middle"></div>
  <div class="position-absolute top-50 start-100 translate-middle"></div>
  <div class="position-absolute top-100 start-0 translate-middle"></div>
  <div class="position-absolute top-100 start-50 translate-middle"></div>
  <div class="position-absolute top-100 start-100 translate-middle"></div>
</div>


<div class="position-relative">
  <div class="position-absolute top-0 start-0"></div>
  <div class="position-absolute top-0 start-50 translate-middle-x"></div>
  <div class="position-absolute top-0 end-0"></div>
  <div class="position-absolute top-50 start-0 translate-middle-y"></div>
  <div class="position-absolute top-50 start-50 translate-middle"></div>
  <div class="position-absolute top-50 end-0 translate-middle-y"></div>
  <div class="position-absolute bottom-0 start-0"></div>
  <div class="position-absolute bottom-0 start-50 translate-middle-x"></div>
  <div class="position-absolute bottom-0 end-0"></div>
</div>

两个炫酷的例子

<button type="button" class="btn btn-primary position-relative">
  Mails <span class="position-absolute top-0 start-100 translate-middle badge rounded-pill bg-secondary">+99 <span class="visually-hidden">unread messages</span></span>
</button>

<button type="button" class="btn btn-dark position-relative">
  Marker <svg width="1em" height="1em" viewBox="0 0 16 16" class="position-absolute top-100 start-50 translate-middle mt-1 bi bi-caret-down-fill" fill="#212529" xmlns="http://www.w3.org/2000/svg"><path d="M7.247 11.14L2.451 5.658C1.885 5.013 2.345 4 3.204 4h9.592a1 1 0 0 1 .753 1.659l-4.796 5.48a1 1 0 0 1-1.506 0z"/></svg>
</button>

<button type="button" class="btn btn-primary position-relative">
  Alerts <span class="position-absolute top-0 start-100 translate-middle badge border border-light rounded-circle bg-danger p-2"><span class="visually-hidden">unread messages</span></span>
</button>

<div class="position-relative m-4">
  <div class="progress" style="height: 1px;">
    <div class="progress-bar" role="progressbar" style="width: 50%;" aria-valuenow="50" aria-valuemin="0" aria-valuemax="100"></div>
  </div>
  <button type="button" class="position-absolute top-0 start-0 translate-middle btn btn-sm btn-primary rounded-pill" style="width: 2rem; height:2rem;">1</button>
  <button type="button" class="position-absolute top-0 start-50 translate-middle btn btn-sm btn-primary rounded-pill" style="width: 2rem; height:2rem;">2</button>
  <button type="button" class="position-absolute top-0 start-100 translate-middle btn btn-sm btn-secondary rounded-pill" style="width: 2rem; height:2rem;">3</button>
</div>