CSS之详解:active选择器

Active的一段话

 active的英文解释为“积极的”，表现在鼠标上就是点击的意思。关于active选择器最多的示例恐怕就是应用在链接上面的，然而打开链接是一个一瞬间的动作，这不能很好的体现active选择器的特点。

 

Active的特点

其实我们打开一个带有active链接，激活acive是有一个过程的，就是点击模块后直到松开模块。如果我们不指定这个过程所花费的时间，笔者认为其默认花费零点几秒。

<span style="font-size: 14px"><span style="color: #0000ff"><span style="color: #ff00ff">DOCTYPE html</span><span style="color: #0000ff">></span>
<span style="color: #0000ff"><span style="color: #800000">html</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"><span style="color: #800000">head</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><span style="color: #800000">title</span><span style="color: #0000ff">></span>a<span style="color: #0000ff"></span><span style="color: #800000">title</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><span style="color: #800000">meta </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="content-type"</span><span style="color: #ff0000"> content</span><span style="color: #0000ff">="text/html; charset=UTF-8"</span><span style="color: #0000ff">></span>
      <span style="color: #0000ff"><span style="color: #800000">style</span><span style="color: #0000ff">></span><span style="color: #800000; background-color: #f5f5f5">
      a</span><span style="color: #000000; background-color: #f5f5f5">{</span><span style="color: #ff0000; background-color: #f5f5f5">
        display</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">block</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        width</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">30px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        margin</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">20px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        border-radius</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">8px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        padding</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">20px 50px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        text-align</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">center</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        background</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">green</span><span style="color: #000000; background-color: #f5f5f5">;</span>
      <span style="color: #000000; background-color: #f5f5f5">}</span><span style="color: #800000; background-color: #f5f5f5">
      a:active</span><span style="color: #000000; background-color: #f5f5f5">{</span><span style="color: #ff0000; background-color: #f5f5f5">
        background</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">indigo</span><span style="color: #000000; background-color: #f5f5f5">;</span>
      <span style="color: #000000; background-color: #f5f5f5">}</span>
    <span style="color: #0000ff"></span><span style="color: #800000">style</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"></span><span style="color: #800000">head</span><span style="color: #0000ff">></span>
  
  <span style="color: #0000ff"><span style="color: #800000">body</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><span style="color: #800000">a </span><span style="color: #ff0000">href</span><span style="color: #0000ff">="paris.jpg"</span><span style="color: #0000ff">></span>link<span style="color: #0000ff"></span><span style="color: #800000">a</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"></span><span style="color: #800000">body</span><span style="color: #0000ff">></span>
<span style="color: #0000ff"></span><span style="color: #800000">html</span><span style="color: #0000ff">></span></span></span></span></span></span></span></span></span></span>

 

我们可以通过过渡属性（transition）来调整这个时间。

<span style="color: #000000; font-size: 14px">      a:active{
        background:indigo;
        transition:3s;
      }</span>

 

读者可以做一个实验，改变其中transition的值，然后测试:avtive选择器所花费的时间。

 

ACTIVE示例

<span style="font-size: 14px"><span style="color: #0000ff"><span style="color: #ff00ff">DOCTYPE html</span><span style="color: #0000ff">></span>
<span style="color: #0000ff"><span style="color: #800000">html</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"><span style="color: #800000">head</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><span style="color: #800000">title</span><span style="color: #0000ff">></span>a<span style="color: #0000ff"></span><span style="color: #800000">title</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><span style="color: #800000">meta </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="content-type"</span><span style="color: #ff0000"> content</span><span style="color: #0000ff">="text/html; charset=UTF-8"</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><span style="color: #800000">style</span><span style="color: #0000ff">></span><span style="color: #800000; background-color: #f5f5f5"> 
       div
      </span><span style="color: #000000; background-color: #f5f5f5">{</span><span style="color: #ff0000; background-color: #f5f5f5">
        width</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">100px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        height</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">100px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        background</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">red</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        transition</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5"> 5s</span><span style="color: #000000; background-color: #f5f5f5">;</span>
       <span style="color: #000000; background-color: #f5f5f5">}</span><span style="color: #800000; background-color: #f5f5f5">

        div:active
       </span><span style="color: #000000; background-color: #f5f5f5">{</span><span style="color: #ff0000; background-color: #f5f5f5">
        width</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">300px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        height</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">300px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        transition</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">3s</span><span style="color: #000000; background-color: #f5f5f5">;</span>
        <span style="color: #000000; background-color: #f5f5f5">}</span>
      <span style="color: #0000ff"></span><span style="color: #800000">style</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"></span><span style="color: #800000">head</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"><span style="color: #800000">body</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"><span style="color: #800000">div</span><span style="color: #0000ff">></span><span style="color: #800000">div</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"></span><span style="color: #800000">body</span><span style="color: #0000ff">></span>
<span style="color: #0000ff"></span><span style="color: #800000">html</span><span style="color: #0000ff">></span>
             </span></span></span></span></span></span></span></span></span>

这里面有两个transition，也就是意味着有两个过渡。

1. 1. 第一个过渡是激活active选择器，这时候 div:avtive 里的 transition 起作用。
   2. 第二个过渡是松开鼠标，图像的尺寸恢复正常的过程，这时候 div 里的 transition 起作用。

如果读者只设置了在 div 里面的 transition ，那么选择器的过渡时间也就默认为 div 里的 transition 了。

 

如果读者有兴趣也可以试一试transition和其他选择器的组合。