还记得我们折腾过的居中么？ - jerrylsxu

虽然div中内容上下居中的问题已经是一个比较古老的话题，但是最近发现还是有很多前端开发者在询问如何实现。其实网络上已经有很多资料和案例了，我这里再总结一下几个比较常见的处理方式。

情形一：div限高，内容长度限一行

<span style="color: #008080;">1</span> <span style="color: #800000;">.v-align </span>{
<span style="color: #008080;">2</span> <span style="color: #ff0000;">    margin</span>:<span style="color: #0000ff;"> 0 auto</span>;
<span style="color: #008080;">3</span> <span style="color: #ff0000;">    width</span>:<span style="color: #0000ff;"> 200px</span>;
<span style="color: #008080;">4</span> <span style="color: #ff0000;">    height</span>:<span style="color: #0000ff;"> 80px</span>;
<span style="color: #008080;">5</span> <span style="color: #ff0000;">    text-align</span>:<span style="color: #0000ff;"> center</span>;
<span style="color: #008080;">6</span> <span style="color: #ff0000;">    line-height</span>:<span style="color: #0000ff;"> 80px</span>;
<span style="color: #008080;">7</span> <span style="color: #ff0000;">    border</span>:<span style="color: #0000ff;"> 1px solid #ddd</span>;
<span style="color: #008080;">8</span> }

<span style="color: #008080;">1</span> <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="v-align"</span><span style="color: #0000ff;">></span>我的内容只能有一行。<span style="color: #0000ff;"></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span></span>

情形二：div限高，内容不限

<span style="color: #008080;"> 1</span> <span style="color: #800000;">.v-mult </span>{
<span style="color: #008080;"> 2</span> <span style="color: #ff0000;">    margin</span>:<span style="color: #0000ff;"> 0 auto</span>;
<span style="color: #008080;"> 3</span> <span style="color: #ff0000;">    width</span>:<span style="color: #0000ff;"> 200px</span>;
<span style="color: #008080;"> 4</span> <span style="color: #ff0000;">    height</span>:<span style="color: #0000ff;"> 100px</span>;
<span style="color: #008080;"> 5</span> <span style="color: #ff0000;">    border</span>:<span style="color: #0000ff;"> 1px solid #ddd</span>;
<span style="color: #008080;"> 6</span> <span style="color: #ff0000;">    overflow</span>:<span style="color: #0000ff;"> hidden</span>;
<span style="color: #008080;"> 7</span> }
<span style="color: #008080;"> 8</span> <span style="color: #800000;">.v-mult .empty,
</span><span style="color: #008080;"> 9</span> <span style="color: #800000;">.v-mult .text </span>{
<span style="color: #008080;">10</span> <span style="color: #ff0000;">    display</span>:<span style="color: #0000ff;"> inline-block</span>;
<span style="color: #008080;">11</span> <span style="color: #ff0000;">    *display</span>:<span style="color: #0000ff;"> inline</span>;
<span style="color: #008080;">12</span> <span style="color: #ff0000;">    *zoom</span>:<span style="color: #0000ff;"> 1</span>;
<span style="color: #008080;">13</span> <span style="color: #ff0000;">    vertical-align</span>:<span style="color: #0000ff;"> middle</span>;
<span style="color: #008080;">14</span> }
<span style="color: #008080;">15</span> <span style="color: #800000;">.v-mult .empty </span>{
<span style="color: #008080;">16</span> <span style="color: #ff0000;">    height</span>:<span style="color: #0000ff;"> 100%</span>;
<span style="color: #008080;">17</span> }

<span style="color: #008080;">1</span> <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="v-mult"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">2</span>     <span style="color: #0000ff;"><span style="color: #800000;">span </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="empty"</span><span style="color: #0000ff;">></span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">3</span>     <span style="color: #0000ff;"><span style="color: #800000;">span </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="text"</span><span style="color: #0000ff;">></span>我的内容不限，多高都行<span style="color: #0000ff;"><span style="color: #800000;">br</span><span style="color: #0000ff;">></span>换行照常<span style="color: #0000ff;"></span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">4</span> <span style="color: #0000ff;"></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span></span></span></span></span>

情形三：div高度不定，内容高度一定

<span style="color: #008080;"> 1</span> <span style="color: #800000;">.v-auto </span>{
<span style="color: #008080;"> 2</span> <span style="color: #ff0000;">    position</span>:<span style="color: #0000ff;"> relative</span>;
<span style="color: #008080;"> 3</span> <span style="color: #ff0000;">    margin</span>:<span style="color: #0000ff;"> 0 auto</span>;
<span style="color: #008080;"> 4</span> <span style="color: #ff0000;">    width</span>:<span style="color: #0000ff;"> 200px</span>;
<span style="color: #008080;"> 5</span> <span style="color: #ff0000;">    border</span>:<span style="color: #0000ff;"> 1px solid #ddd</span>;
<span style="color: #008080;"> 6</span> }
<span style="color: #008080;"> 7</span> <span style="color: #800000;">.v-auto .text </span>{
<span style="color: #008080;"> 8</span> <span style="color: #ff0000;">    position</span>:<span style="color: #0000ff;"> absolute</span>;
<span style="color: #008080;"> 9</span> <span style="color: #ff0000;">    top</span>:<span style="color: #0000ff;"> 50%</span>;
<span style="color: #008080;">10</span> <span style="color: #ff0000;">    margin-top</span>:<span style="color: #0000ff;"> -50px</span>;
<span style="color: #008080;">11</span> <span style="color: #ff0000;">    height</span>:<span style="color: #0000ff;"> 100px</span>;
<span style="color: #008080;">12</span> <span style="color: #ff0000;">    border</span>:<span style="color: #0000ff;"> 1px dashed #ddd</span>;
<span style="color: #008080;">13</span> }

<span style="color: #008080;">1</span> <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="v-auto"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">2</span>     <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="text"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">3</span> <span style="color: #000000;">        我的高度是固定的，只有100px高，但是我的父及高度不定，我怎么垂直居中呢？
</span><span style="color: #008080;">4</span>     <span style="color: #0000ff;"></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">5</span>     <span style="color: #0000ff;"><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">6</span> <span style="color: #0000ff;"></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span></span></span></span></span></span></span></span></span></span></span>

情形四：div高度不定，内容高度不定

<span style="color: #008080;"> 1</span> <span style="color: #800000;">.v-auto-out </span>{
<span style="color: #008080;"> 2</span> <span style="color: #ff0000;">    position</span>:<span style="color: #0000ff;"> relative</span>;
<span style="color: #008080;"> 3</span> <span style="color: #ff0000;">    margin</span>:<span style="color: #0000ff;"> 0 auto</span>;
<span style="color: #008080;"> 4</span> <span style="color: #ff0000;">    width</span>:<span style="color: #0000ff;"> 200px</span>;
<span style="color: #008080;"> 5</span> <span style="color: #ff0000;">    border</span>:<span style="color: #0000ff;"> 1px solid #ddd</span>;
<span style="color: #008080;"> 6</span> }
<span style="color: #008080;"> 7</span> <span style="color: #800000;">.v-auto-out .auto-in </span>{
<span style="color: #008080;"> 8</span> <span style="color: #ff0000;">    position</span>:<span style="color: #0000ff;"> absolute</span>;
<span style="color: #008080;"> 9</span> <span style="color: #ff0000;">    top</span>:<span style="color: #0000ff;"> 50%</span>;
<span style="color: #008080;">10</span> <span style="color: #ff0000;">    border</span>:<span style="color: #0000ff;"> 1px dashed #ddd</span>;
<span style="color: #008080;">11</span>     <span style="color: #008000;">/*</span><span style="color: #008000;"> 这里有兼容性问题 </span><span style="color: #008000;">*/</span>
<span style="color: #008080;">12</span> <span style="color: #ff0000;">    -webkit-transform</span>:<span style="color: #0000ff;"> translateY(-50%)</span>;
<span style="color: #008080;">13</span> <span style="color: #ff0000;">    -ms-transform</span>:<span style="color: #0000ff;"> translateY(-50%)</span>;
<span style="color: #008080;">14</span> <span style="color: #ff0000;">    -o-transform</span>:<span style="color: #0000ff;"> translateY(-50%)</span>;
<span style="color: #008080;">15</span> <span style="color: #ff0000;">    transform</span>:<span style="color: #0000ff;"> translateY(-50%)</span>;
<span style="color: #008080;">16</span> }

<span style="color: #008080;">1</span> <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="v-auto-out"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">2</span>     <span style="color: #0000ff;"><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="auto-in"</span><span style="color: #0000ff;">></span>我的高度不定，我的父及高度也不定，这下要上下居中，该如何是好？我们一起来瞧瞧吧。<span style="color: #0000ff;"></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">3</span>     <span style="color: #0000ff;"><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">><span style="color: #800000;">br</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">4</span> <span style="color: #0000ff;"></span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span></span></span></span></span></span></span></span></span></span></span></span>

好了，知道这四种方式，我相信足以应对日常工作中的各种垂直居中问题。代码很简单，不再做多余阐述。总之一句话，CSS的各个属性样式，就好像人肢体的各个器官，了解了各个器官的功能，才能相互配合完成各种任务。相反，个体的能力是有限的。

作者博客：http://www.seejs.com