flex.css快速入门，极速布局

什么是flex.css?

css3 flex 布局相信很多人已经听说过甚至已经在开发中使用过它，但是我想我们都会有一个共同的经历，面对它的各种版本，各种坑，傻傻的分不清楚，flex.css就是对flex布局的一种封装，通过简洁的属性设置就能使得它完美的运行在移动端的各种浏览器，甚至能运行在ie10 的各种PC端浏览器中。它天然的能够很好的将页面布局和css进行分离，让css专注于元素的显示效果，我称之为声明式布局......

flex和data-flex

flex.css 有两个版本，一个是flex.css一个是data-flex.css，这两个版本其实是一样的，唯一的区别是，一个是使用flex属性设置，一个是使用data-flex属性设置。react 不支持flex属性直接布局，所以data-flex.css实际上是为了react而诞生的

安装flex.css

官方地址：https://github.com/lzxb/flex.css

通过npm安装：

npm install --save flex.css

本例子教程例子，则是从官方项目下载下来后，解压出来后，将dist目录下的flex.css文件引入使用

Hello world

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><title>Hello world</title><link rel="stylesheet" href="./flex.css"><style type="text/css">.box {width: 150px;height: 150px;border: 1px solid #ddd;}</style>
</head><body><div class="box" flex>Hello world</div>
</body></html>

设置主轴方向

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><title>设置主轴方向</title><link rel="stylesheet" href="./flex.css"><style type="text/css">.box {width: 150px;height: 150px;border: 1px solid #ddd;}.item {width: 30px;height: 30px;line-height: 30px;color: #fff;text-align: center;}</style>
</head><body><h2>从上到下</h2><div class="box" flex="dir:top"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>从右到左</h2><div class="box" flex="dir:right"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>从下到上</h2><div class="box" flex="dir:bottom"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>从左到右（默认）</h2><div class="box" flex="dir:left"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div>
</body></html>

主轴对齐方式

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><title>主轴对齐方式</title><link rel="stylesheet" href="./flex.css"><style type="text/css">.box {width: 150px;height: 150px;border: 1px solid #ddd;}.item {width: 30px;height: 30px;line-height: 30px;color: #fff;text-align: center;}</style>
</head><body><h2>从右到左</h2><div class="box" flex="main:right"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>从左到右（默认）</h2><div class="box" flex="main:left"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>两端对齐</h2><div class="box" flex="main:justify"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>居中对齐</h2><div class="box" flex="main:center"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div>
</body></html>

交叉轴对齐方式

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><title>交叉轴对齐方式</title><link rel="stylesheet" href="./flex.css"><style type="text/css">.box {width: 150px;height: 150px;border: 1px solid #ddd;}.item {width: 30px;/*height: 30px;*/line-height: 30px;color: #fff;text-align: center;}</style>
</head><body><h2>从上到下（默认）</h2><div class="box" flex="cross:top"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>从下到上</h2><div class="box" flex="cross:bottom"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>基线对齐</h2><div class="box" flex="cross:baseline"><div class="item" style="font-size: 30px; background: red;">1</div><div class="item" style="font-size: 12px; background: blue;">2</div><div class="item" style="font-size: 40px; background: #000;">3</div></div><h2>居中对齐</h2><div class="box" flex="cross:center"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>高度并排铺满</h2><div class="box" flex="cross:stretch"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div>
</body></html>

子元素设置

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><title>交叉轴对齐方式</title><link rel="stylesheet" href="./flex.css"><style type="text/css">.box {width: 150px;height: 150px;border: 1px solid #ddd;}.item {width: 30px;height: 30px;line-height: 30px;color: #fff;text-align: center;}</style>
</head><body><h2>子元素平分空间</h2><div class="box" flex="box:mean"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>第一个子元素不要多余空间，其他子元素平分多余空间</h2><div class="box" flex="box:first"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>最后一个子元素不要多余空间，其他子元素平分多余空间</h2><div class="box" flex="box:last"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div><h2>两端第一个元素不要多余空间，其他子元素平分多余空间</h2><div class="box" flex="box:justify"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div>
</body></html>

flex-box元素剩余空间比例分配

取值范围(0-10)，单独设置子元素多余空间的如何分配，设置为0，则子元素不占用多余的多余空间

多余空间分配 = 当前flex-box值/子元素的flex-box值相加之和

flex-box实现两端不需要多余空间，中间占满剩余空间

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><title>flex-box实现两端不需要多余空间，中间占满剩余空间</title><link rel="stylesheet" href="./flex.css"><style type="text/css">.box {width: 150px;height: 150px;border: 1px solid #ddd;}.item {width: 30px;height: 30px;line-height: 30px;color: #fff;text-align: center;}</style>
</head><body><h2>flex-box实现两端不需要多余空间，中间占满剩余空间</h2><div class="box" flex><div class="item" flex-box="0" style="background: red;">1</div><div class="item" flex-box="1" style="background: blue;">2</div><div class="item" flex-box="0" style="background: #000;">3</div></div>
</body></html>

水平居中

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><title>水平居中</title><link rel="stylesheet" href="./flex.css"><style type="text/css">.box {width: 150px;height: 150px;border: 1px solid #ddd;}.item {width: 30px;height: 30px;line-height: 30px;color: #fff;text-align: center;}</style>
</head><body><h2>水平居中</h2><div class="box" flex="main:center cross:center"><div class="item" style="background: red;">1</div><div class="item" style="background: blue;">2</div><div class="item" style="background: #000;">3</div></div>
</body></html>