2018-10-10 22:03:03 +00:00
|
|
|
|
---
|
|
|
|
|
|
id: 587d778d367417b2b2512aaa
|
2020-12-16 07:37:30 +00:00
|
|
|
|
title: 使用自定义 CSS 让元素仅对屏幕阅读器可见
|
2018-10-10 22:03:03 +00:00
|
|
|
|
challengeType: 0
|
2020-02-11 09:06:41 +00:00
|
|
|
|
videoUrl: 'https://scrimba.com/c/cJ8QGkhJ'
|
|
|
|
|
|
forumTopicId: 301020
|
2021-01-13 02:31:00 +00:00
|
|
|
|
dashedName: make-elements-only-visible-to-a-screen-reader-by-using-custom-css
|
2018-10-10 22:03:03 +00:00
|
|
|
|
---
|
|
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
# --description--
|
|
|
|
|
|
|
2020-02-11 09:06:41 +00:00
|
|
|
|
到目前为止，所有关于可访问性的挑战都没有使用 CSS。这是为了让你在关注外观样式之前，先把页面的逻辑结构写清，以及明确语义化标签的重要性。
|
2020-12-16 07:37:30 +00:00
|
|
|
|
|
2021-01-08 19:20:48 +00:00
|
|
|
|
但如果我们想在页面中添加一些只对屏幕阅读器可见的内容，此时我们可以用 CSS 来实现。当信息以可视化形式（比如图表）展示，而屏幕阅读器用户需要另一种方式（比如表格）来获取信息时，我们就可以用 CSS 来解决这个问题：只需要把仅供屏幕阅读器使用的信息通过 CSS 定位到浏览器可见区域之外即可。
|
2020-12-16 07:37:30 +00:00
|
|
|
|
|
2020-02-11 09:06:41 +00:00
|
|
|
|
举个例子：
|
|
|
|
|
|
|
|
|
|
|
|
```css
|
|
|
|
|
|
.sr-only {
|
|
|
|
|
|
position: absolute;
|
|
|
|
|
|
left: -10000px;
|
|
|
|
|
|
width: 1px;
|
|
|
|
|
|
height: 1px;
|
|
|
|
|
|
top: auto;
|
|
|
|
|
|
overflow: hidden;
|
|
|
|
|
|
}
|
|
|
|
|
|
```
|
|
|
|
|
|
|
2021-01-08 19:20:48 +00:00
|
|
|
|
**注意：**以下的 CSS 解决方案与上面的结果不同：
|
2020-12-16 07:37:30 +00:00
|
|
|
|
|
2020-02-11 09:06:41 +00:00
|
|
|
|
<ul>
|
2021-01-08 19:20:48 +00:00
|
|
|
|
<li><code>display: none;</code> 或 <code>visibility: hidden;</code> 会把内容彻底隐藏起来，屏幕阅读器也无法获取这些内容。</li>
|
|
|
|
|
|
<li>如果把值设置为 0px，如 <code>width: 0px; height: 0px;</code>，意味着让元素脱离文档流，这样做同样也会让屏幕阅读器忽略此元素。</li>
|
2020-02-11 09:06:41 +00:00
|
|
|
|
</ul>
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
# --instructions--
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2021-01-08 19:20:48 +00:00
|
|
|
|
Camper Cat 为他的训练页面创建了一个十分酷炫的条形图。考虑到可访问性，他还将数据放入到了一个表格中，供屏幕阅读器用户使用。表格的 `class` 为 `sr-only`，但是还没有添加 CSS 规则。请将 `position` 的值设置为 absolute、`left` 的值设置为 -10000px、`width` 与 `height` 的值均设置为 1px。
|
2020-12-16 07:37:30 +00:00
|
|
|
|
|
|
|
|
|
|
# --hints--
|
|
|
|
|
|
|
2021-01-08 19:20:48 +00:00
|
|
|
|
`class` 为 `sr-only` 的元素的 `position` 属性值应为 absolute。
|
2020-12-16 07:37:30 +00:00
|
|
|
|
|
|
|
|
|
|
```js
|
|
|
|
|
|
assert($('.sr-only').css('position') == 'absolute');
|
2018-10-10 22:03:03 +00:00
|
|
|
|
```
|
|
|
|
|
|
|
2021-01-08 19:20:48 +00:00
|
|
|
|
`class` 为 `sr-only` 的元素的 `left` 属性值应为 -10000px。
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
```js
|
|
|
|
|
|
assert($('.sr-only').css('left') == '-10000px');
|
|
|
|
|
|
```
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2021-01-08 19:20:48 +00:00
|
|
|
|
`class` 为 `sr-only` 的元素的 `width` 属性值应为 1px。
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
```js
|
|
|
|
|
|
assert(code.match(/width:\s*?1px/gi));
|
|
|
|
|
|
```
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2021-01-08 19:20:48 +00:00
|
|
|
|
`class` 为 `sr-only` 的元素的 `height` 属性值应为 1px。
|
2018-10-10 22:03:03 +00:00
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
```js
|
|
|
|
|
|
assert(code.match(/height:\s*?1px/gi));
|
2018-10-10 22:03:03 +00:00
|
|
|
|
```
|
2020-02-11 09:06:41 +00:00
|
|
|
|
|
2021-01-13 02:31:00 +00:00
|
|
|
|
# --seed--
|
|
|
|
|
|
|
|
|
|
|
|
## --seed-contents--
|
|
|
|
|
|
|
|
|
|
|
|
```html
|
|
|
|
|
|
<head>
|
|
|
|
|
|
<style>
|
|
|
|
|
|
.sr-only {
|
|
|
|
|
|
position: ;
|
|
|
|
|
|
left: ;
|
|
|
|
|
|
width: ;
|
|
|
|
|
|
height: ;
|
|
|
|
|
|
top: auto;
|
|
|
|
|
|
overflow: hidden;
|
|
|
|
|
|
}
|
|
|
|
|
|
</style>
|
|
|
|
|
|
</head>
|
|
|
|
|
|
<body>
|
|
|
|
|
|
<header>
|
|
|
|
|
|
<h1>Training</h1>
|
|
|
|
|
|
<nav>
|
|
|
|
|
|
<ul>
|
|
|
|
|
|
<li><a href="#stealth">Stealth & Agility</a></li>
|
|
|
|
|
|
<li><a href="#combat">Combat</a></li>
|
|
|
|
|
|
<li><a href="#weapons">Weapons</a></li>
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
</nav>
|
|
|
|
|
|
</header>
|
|
|
|
|
|
<section>
|
|
|
|
|
|
<h2>Master Camper Cat's Beginner Three Week Training Program</h2>
|
|
|
|
|
|
<figure>
|
|
|
|
|
|
<!-- Stacked bar chart of weekly training -->
|
|
|
|
|
|
<p>[Stacked bar chart]</p>
|
|
|
|
|
|
<br />
|
|
|
|
|
|
<figcaption>Breakdown per week of time to spend training in stealth, combat, and weapons.</figcaption>
|
|
|
|
|
|
</figure>
|
|
|
|
|
|
<table class="sr-only">
|
|
|
|
|
|
<caption>Hours of Weekly Training in Stealth, Combat, and Weapons</caption>
|
|
|
|
|
|
<thead>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th></th>
|
|
|
|
|
|
<th scope="col">Stealth & Agility</th>
|
|
|
|
|
|
<th scope="col">Combat</th>
|
|
|
|
|
|
<th scope="col">Weapons</th>
|
|
|
|
|
|
<th scope="col">Total</th>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
</thead>
|
|
|
|
|
|
<tbody>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th scope="row">Week One</th>
|
|
|
|
|
|
<td>3</td>
|
|
|
|
|
|
<td>5</td>
|
|
|
|
|
|
<td>2</td>
|
|
|
|
|
|
<td>10</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th scope="row">Week Two</th>
|
|
|
|
|
|
<td>4</td>
|
|
|
|
|
|
<td>5</td>
|
|
|
|
|
|
<td>3</td>
|
|
|
|
|
|
<td>12</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th scope="row">Week Three</th>
|
|
|
|
|
|
<td>4</td>
|
|
|
|
|
|
<td>6</td>
|
|
|
|
|
|
<td>3</td>
|
|
|
|
|
|
<td>13</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
</tbody>
|
|
|
|
|
|
</table>
|
|
|
|
|
|
</section>
|
|
|
|
|
|
<section id="stealth">
|
|
|
|
|
|
<h2>Stealth & Agility Training</h2>
|
|
|
|
|
|
<article><h3>Climb foliage quickly using a minimum spanning tree approach</h3></article>
|
|
|
|
|
|
<article><h3>No training is NP-complete without parkour</h3></article>
|
|
|
|
|
|
</section>
|
|
|
|
|
|
<section id="combat">
|
|
|
|
|
|
<h2>Combat Training</h2>
|
|
|
|
|
|
<article><h3>Dispatch multiple enemies with multithreaded tactics</h3></article>
|
|
|
|
|
|
<article><h3>Goodbye, world: 5 proven ways to knock out an opponent</h3></article>
|
|
|
|
|
|
</section>
|
|
|
|
|
|
<section id="weapons">
|
|
|
|
|
|
<h2>Weapons Training</h2>
|
|
|
|
|
|
<article><h3>Swords: the best tool to literally divide and conquer</h3></article>
|
|
|
|
|
|
<article><h3>Breadth-first or depth-first in multi-weapon training?</h3></article>
|
|
|
|
|
|
</section>
|
|
|
|
|
|
<footer>© 2018 Camper Cat</footer>
|
|
|
|
|
|
</body>
|
|
|
|
|
|
```
|
|
|
|
|
|
|
2020-12-16 07:37:30 +00:00
|
|
|
|
# --solutions--
|
|
|
|
|
|
|
2021-01-13 02:31:00 +00:00
|
|
|
|
```html
|
|
|
|
|
|
<head>
|
|
|
|
|
|
<style>
|
|
|
|
|
|
.sr-only {
|
|
|
|
|
|
position: absolute;
|
|
|
|
|
|
left: -10000px;
|
|
|
|
|
|
width: 1px;
|
|
|
|
|
|
height: 1px;
|
|
|
|
|
|
top: auto;
|
|
|
|
|
|
overflow: hidden;
|
|
|
|
|
|
}
|
|
|
|
|
|
</style>
|
|
|
|
|
|
</head>
|
|
|
|
|
|
<body>
|
|
|
|
|
|
<header>
|
|
|
|
|
|
<h1>Training</h1>
|
|
|
|
|
|
<nav>
|
|
|
|
|
|
<ul>
|
|
|
|
|
|
<li><a href="#stealth">Stealth & Agility</a></li>
|
|
|
|
|
|
<li><a href="#combat">Combat</a></li>
|
|
|
|
|
|
<li><a href="#weapons">Weapons</a></li>
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
</nav>
|
|
|
|
|
|
</header>
|
|
|
|
|
|
<section>
|
|
|
|
|
|
<h2>Master Camper Cat's Beginner Three Week Training Program</h2>
|
|
|
|
|
|
<figure>
|
|
|
|
|
|
<!-- Stacked bar chart of weekly training -->
|
|
|
|
|
|
<p>[Stacked bar chart]</p>
|
|
|
|
|
|
<br />
|
|
|
|
|
|
<figcaption>Breakdown per week of time to spend training in stealth, combat, and weapons.</figcaption>
|
|
|
|
|
|
</figure>
|
|
|
|
|
|
<table class="sr-only">
|
|
|
|
|
|
<caption>Hours of Weekly Training in Stealth, Combat, and Weapons</caption>
|
|
|
|
|
|
<thead>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th></th>
|
|
|
|
|
|
<th scope="col">Stealth & Agility</th>
|
|
|
|
|
|
<th scope="col">Combat</th>
|
|
|
|
|
|
<th scope="col">Weapons</th>
|
|
|
|
|
|
<th scope="col">Total</th>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
</thead>
|
|
|
|
|
|
<tbody>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th scope="row">Week One</th>
|
|
|
|
|
|
<td>3</td>
|
|
|
|
|
|
<td>5</td>
|
|
|
|
|
|
<td>2</td>
|
|
|
|
|
|
<td>10</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th scope="row">Week Two</th>
|
|
|
|
|
|
<td>4</td>
|
|
|
|
|
|
<td>5</td>
|
|
|
|
|
|
<td>3</td>
|
|
|
|
|
|
<td>12</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th scope="row">Week Three</th>
|
|
|
|
|
|
<td>4</td>
|
|
|
|
|
|
<td>6</td>
|
|
|
|
|
|
<td>3</td>
|
|
|
|
|
|
<td>13</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
</tbody>
|
|
|
|
|
|
</table>
|
|
|
|
|
|
</section>
|
|
|
|
|
|
<section id="stealth">
|
|
|
|
|
|
<h2>Stealth & Agility Training</h2>
|
|
|
|
|
|
<article><h3>Climb foliage quickly using a minimum spanning tree approach</h3></article>
|
|
|
|
|
|
<article><h3>No training is NP-complete without parkour</h3></article>
|
|
|
|
|
|
</section>
|
|
|
|
|
|
<section id="combat">
|
|
|
|
|
|
<h2>Combat Training</h2>
|
|
|
|
|
|
<article><h3>Dispatch multiple enemies with multithreaded tactics</h3></article>
|
|
|
|
|
|
<article><h3>Goodbye, world: 5 proven ways to knock out an opponent</h3></article>
|
|
|
|
|
|
</section>
|
|
|
|
|
|
<section id="weapons">
|
|
|
|
|
|
<h2>Weapons Training</h2>
|
|
|
|
|
|
<article><h3>Swords: the best tool to literally divide and conquer</h3></article>
|
|
|
|
|
|
<article><h3>Breadth-first or depth-first in multi-weapon training?</h3></article>
|
|
|
|
|
|
</section>
|
|
|
|
|
|
<footer>© 2018 Camper Cat</footer>
|
|
|
|
|
|
</body>
|
|
|
|
|
|
```
|
