如何实现CSS居中？–CSS居中常用方法

文章参考：http://css-tricks.com/centering-css-complete-guide/?utm_source=ourjs.com（翻译不当之处请谅解）

一、水平居中

1、内联元素居中：相对父级块级元素居中对齐

1: .center-children {2: text-align: center;3: }

2、块级元素居中：设置margin-left和margin-right为auto让它居中（同时还要设置width，否则它就会承满整个容器，无法看出居中效果）

1: .center-me {2: margin: 0 auto;3: }

如果有很多块级元素需要水平居中成一行，最好使用一个不同的display类型。这是一个使用inline-block和flex的例子。

演示地址：http://jsfiddle.net/Web_Code/5fvrwwk1/embedded/result/

1: <main class="inline-block-center">2: <div>3: I'm an element that is block-like with my siblings and we're centered in a row.4: </div>5: <div>6: I'm an element that is block-like with my siblings and we're centered in a row. I have more content in me than my siblings do.7: </div>8: <div>9: I'm an element that is block-like with my siblings and we're centered in a row.10: </div>11: </main>12: <main class="flex-center">13: <div>14: I'm an element that is block-like with my siblings and we're centered in a row.15: </div>16: <div>17: I'm an element that is block-like with my siblings and we're centered in a row. I have more content in me than my siblings do.18: </div>19: <div>20: I'm an element that is block-like with my siblings and we're centered in a row.21: </div>22: </main>

css:

1: body {2: background: #f06d06;3: font-size: 80%;4: }5: main {6: background: white;7: margin: 20px 0;8: padding: 10px;9: }10: main div {11: background: black;12: color: white;13: padding: 15px;14: max-width: 125px;15: margin: 5px;16: }17: .inline-block-center {18: text-align: center;19: }20: .inline-block-center div {21: display: inline-block;22: text-align: left;23: }24: .flex-center {25: display: flex;26: justify-content: center;27: }

二、垂直居中

1、内联元素：设置相等的上下padding，或者利用line-height

1: .link {2: padding-top: 30px;3: padding-bottom: 30px;4: }

文本不会换行的情况下，可以使用line-height，让其与height相等去对齐文本。

1: .center-text-trick {2: height: 100px;3: line-height: 100px;4: white-space: nowrap;5: }

多行的文本也可以利用上下等padding的方式也可以让多行居中，但是如果这方法没用，你可以让这些文字的容器按table cell模式显示，然后设置文字的vertical-align属性对齐，
演示地址：http://jsfiddle.net/Web_Code/5fvrwwk1/1/embedded/result/
html:

1: <table>2: <tr>3: <td>4: I'm vertically centered multiple lines of text in a real table cell.5: </td>6: </tr>7: </table>8: <div class="center-table">9: <p>I'm vertically centered multiple lines of text in a CSS-created table layout.</p>10: </div>

css

1: body {2: background: #f06d06;3: font-size: 80%;4: }5: table {6: background: white;7: width: 240px;8: border-collapse: separate;9: margin: 20px;10: height: 250px;11: }12: table td {13: background: black;14: color: white;15: padding: 20px;16: border: 10px solid white;17: /* default is vertical-align: middle; */18: }19: .center-table {20: display: table;21: height: 250px;22: background: white;23: width: 240px;24: margin: 20px;25: }26: .center-table p {27: display: table-cell;28: margin: 0;29: background: black;30: color: white;31: padding: 20px;32: border: 10px solid white;33: vertical-align: middle;34: }

2、块级元素

若元素有固定高度，可以这样垂直居中

1: .parent {2: position: relative;3: }4: .child {5: position: absolute;6: top: 50%;7: height: 100px;8: margin-top: -50px; /* 如果没有使用: border-box; 的盒子模型则需要设置这个 */9: }

如果不知道元素高度，则这样

1: .parent {2: position: relative;3: }4: .child {5: position: absolute;6: top: 50%;7: transform: translateY(-50%);8: }

也可以使用flexbox

1: <main>2: <div>3: I'm a block-level element with an unknown height, centered vertically within my parent.4: </div>5: </main>1: body {2: background: #f06d06;3: font-size: 80%;4: }5: main {6: background: white;7: height: 300px;8: width: 200px;9: padding: 20px;10: margin: 20px;11: display: flex;12: flex-direction: column;13: justify-content: center;14: resize: vertical;15: overflow: auto;16: }17: main div {18: background: black;19: color: white;20: padding: 20px;21: resize: vertical;22: overflow: auto;23: }

三、同时水平和垂直居中

1、元素有固定高度和宽度：先绝对居中，然后上移和左移50%的宽度即可

1: //这种方案有极好的跨浏览器支持。2: .parent {3: position: relative;4: }5: .child {6: width: 300px;7: height: 100px;8: padding: 20px;9: position: absolute;10: top: 50%;11: left: 50%;12: margin: -70px 0 0 -170px;13: }

2、元素的高度和宽度未知或可变的：使用transofrm属性在两个方向都平移负50%

1: .parent {2: position: relative;3: }4: .child {5: position: absolute;6: top: 50%;7: left: 50%;8: transform: translate(-50%, -50%);9: }

原文首发：http://www.ido321.com/824.html

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