## calc实现 css两端固定大小，中间自动大小##

1. 样式代码

<style type="text/css">.wrap{ height:300px; width:400px; background:#e0e0e0;}.top{ height:50px; border:solid 1px #f0f0f0;}.midle{ height:calc(100% - 100px)}.bottom{ height:50px; border:solid 1px #f0f0f0;}</style>

1. ui界面代码

<div class="wrap"> <div class="top"> top wrap </div> <div class="midle"> midle wrap </div> <div class="bottom"> bottom wrap </div></div>