Bootstrap3基础教程 02 网格布局
Bootstrap 提供了一套响应式、移动设备优先的流式网格系统，随着屏幕或视口（viewport）尺寸的增加，系统会自动分为最多12列。
网页设计中的网格布局作用：组织内容，让网站易于浏览，并降低用户端的负载。
Grid System
Bootstrap 包含了一个响应式的、移动设备优先的、不固定的网格系统，可以随着设备或视口大小的增加而适当地扩展到 12 列。它包含了用于简单的布局选项的预定义类，也包含了用于生成更多语义布局的功能强大的混合类。
移动设备优先策略：
1.基础的 CSS 是移动设备优先，媒体查询是针对于平板电脑、台式电脑。
2.随着屏幕大小的增加而添加元素。
3.优先设计更小的宽度。
Grid System 工作原理
1.行必须放置在 .container class 内，以便获得适当的对齐（alignment）和内边距（padding）。
2.使用行来创建列的水平组。
3.内容应该放置在列内，且唯有列可以是行的直接子元素。
4.预定义的网格类，比如 .row 和 .col-xs-4，可用于快速创建网格布局。LESS 混合类可用于更多语义布局。
5.列通过内边距（padding）来创建列内容之间的间隙。该内边距是通过 .rows 上的外边距（margin）取负，表示第一列和最后一列的行偏移。
6.网格系统是通过指定您想要横跨的十二个可用的列来创建的。例如，要创建三个相等的列，则使用三个 .col-xs-4。
媒体查询
媒体查询是非常别致的"有条件的 CSS 规则"。它只适用于一些基于某些规定条件的 CSS。如果满足那些条件，则应用相应的样式。
/* 超小设备（手机，小于 768px） */
/* Bootstrap 中默认情况下没有媒体查询 */
/* 小型设备（平板电脑，768px 起） */
@media (min-width: @screen-sm-min) { ... }
/* 中型设备（台式电脑，992px 起） */
@media (min-width: @screen-md-min) { ... }
/* 大型设备（大台式电脑，1200px 起） */
@media (min-width: @screen-lg-min) { ... }有时候也会在媒体查询代码中包含 max-width，从而将 CSS 的影响限制在更小范围的屏幕大小之内。
@media (max-width: @screen-xs-max) { ... }
@media (min-width: @screen-sm-min) and (max-width: @screen-sm-max) { ... }
@media (min-width: @screen-md-min) and (max-width: @screen-md-max) { ... }
@media (min-width: @screen-lg-min) { ... }网格选项
.col-xs- 超小设备手机（<768px）
.col-sm- 小型设备平板电脑（≥768px）
.col-md- 中型设备台式电脑（≥992px）
.col-lg- 大型设备台式电脑（≥1200px）
代码
01 页面居中显示的容器
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge"><!--告诉IE浏览器用最新的引擎-->
<meta name="viewport" content="width=device-width, initial-scale=1"><!--响应式布局-->
<link href="bootstrap/css/bootstrap.min.css" rel="stylesheet" /><!--bootstrap样式-->
<title></title>
</head>
<body>
<div class="container">
<h1 class="page-header">主体</h1>
<p>Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.</p>
</div>
<script src="Script/jquery-1.8.3.js"></script><!--Bootstrap 的所有 JavaScript 插件都依赖 jQuery，所以必须放在前边-->
<script src="bootstrap/js/bootstrap.min.js"></script><!--Bootstrap 的所有 JavaScript 插件-->
</body>
</html>class：page-header，container
.page-header {
padding-bottom: 9px;
margin: 40px 0 20px;
border-bottom: 1px solid #eee;
}
.container {
padding-right: 15px;
padding-left: 15px;
margin-right: auto;
margin-left: auto;
}
@media (min-width: 768px) {
.container {
width: 750px;
}
}
@media (min-width: 992px) {
.container {
width: 970px;
}
}
@media (min-width: 1200px) {
.container {
width: 1170px;
}
}02 网格类
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="bootstrap/css/bootstrap.min.css" rel="stylesheet" />
<title></title>
</head>
<body>
<div class="container">
<div class="row">
<!--
col-lg-6 >=1200px
col-md-8 >=992px
col-sm-6 >=768px
col-xs-6 <798px
-->
<div class="col-md-8 col-sm-6">
<h1 class="page-header">主体</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
<div class="col-md-4 col-sm-6">
<h1 class="page-header">边栏</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
</div>
</div>
<script src="Script/jquery-1.8.3.js"></script>
<script src="bootstrap/js/bootstrap.min.js"></script>
</body>
</html>03 混合使用网格类
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="bootstrap/css/bootstrap.min.css" rel="stylesheet" />
<title></title>
</head>
<body>
<div class="container">
<div class="row">
<!--
col-lg-6 >=1200px
col-md-8 >=992px
col-sm-6 >=768px
col-xs-6 <798px
-->
<div class="col-md-9 col-sm-8 col-xs-6 col-lg-10">
<h1 class="page-header">主体</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
<div class="col-md-3 col-sm-4 col-xs-6 col-lg-2">
<h1 class="page-header">边栏</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
</div>
</div>
<script src="Script/jquery-1.8.3.js"></script>
<script src="bootstrap/js/bootstrap.min.js"></script>
</body>
</html>04 push和pull
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="bootstrap/css/bootstrap.min.css" rel="stylesheet" />
<title></title>
</head>
<body>
<div class="container">
<div class="row">
<div class="col-md-9 col-md-push-3"><!--col-md-push-3：中等尺寸往右推3个网格-->
<h1 class="page-header">主体</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
<div class="col-md-3 col-md-pull-9"><!--col-md-pull-9:中等尺寸往左拉9个网格-->
<h1 class="page-header">边栏</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
</div>
</div>
<script src="Script/jquery-1.8.3.js"></script>
<script src="bootstrap/js/bootstrap.min.js"></script>
</body>
</html>05 嵌套的布局
class:clearfix 清除浮动 or 每行网格都放在 class:row中的div中
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="bootstrap/css/bootstrap.min.css" rel="stylesheet" />
<title></title>
</head>
<body>
<div class="container">
<div class="row">
<div class="col-md-8">
<h1 class="page-header">主体</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
<div class="row">
<div class="col-md-4">
<h1 class="page-header">区块1</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
<div class="col-md-4">
<h1 class="page-header">区块2</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
<div class="col-md-4">
<h1 class="page-header">区块3</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
<div class="clearfix"></div>
<div class="col-md-6">
<h1 class="page-header">区块4</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
<div class="col-md-6">
<h1 class="page-header">区块5</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
</div>
</div>
<div class="col-md-4">
<h1 class="page-header">边栏</h1>
<p>
Use this document as a way to quickly start any new project.
All you get is this text and a mostly barebones HTML document.
</p>
</div>
</div>
</div>
<script src="Script/jquery-1.8.3.js"></script>
<script src="bootstrap/js/bootstrap.min.js"></script>
</body>
</html>