媒体对象

Bootstrap的媒体对象的文档和示例，媒体对象是一些抽象元素，是用来建立一些略显复杂繁琐同时又高度重复使用的组件（比如说博客评论、推文模块等）之基础。它支持左对齐内容、右对齐内容、内容对齐选项、嵌套等。

示例

媒体对象用于构建复杂、重复的内容列表，左边是一个图、右边是内容且不能转着图、形成两列。由于采用了flexbox流式布局，我们只要两个Class类就能达成。

以下是一个媒体对象的示例，只需要两个Class选择器，分别引用.media和.media-body来装载的内容，就可以实现页面设计目标、形成布局、间距并控制可选的填充和边距。

<div class="media">
  <img class="mr-3" src="..." alt="Generic placeholder image">
  <div class="media-body">
    <h5 class="mt-0">Media heading</h5>
    Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.
  </div>
</div>

Flex流式布局第#12号BUG: 内联元素不被视为弹性项目。

Internet Explorer 10-11 不会使内联元素类似的链接或图片（及::before 、 ::after伪元素）作为柔性丰局对象，解决方法是设置一个非内联的display 值 (如block、 inline-block、 flex). 也可以使用BootStrap提供的 响应式实用程序的.d-flex方法处理解决。

资料来源:Flexbugs on GitHub

嵌套

媒体对象可以无限嵌套，尽管我们建议您在某些时候尽量减少网页的嵌套层级，但它在技术原理上来说是合法的，嵌套.media在.media-body下面即可:

<div class="media">
  <img class="mr-3" src="..." alt="Generic placeholder image">
  <div class="media-body">
    <h5 class="mt-0">Media heading</h5>
    Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.
    <div class="media mt-3">
      <a class="pr-3" href="#">
        <img src="..." alt="Generic placeholder image">
      </a>
      <div class="media-body">
        <h5 class="mt-0">Media heading</h5>
        Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.
      </div>
    </div>
  </div>
</div>

对齐

M媒体对象中的媒体可以与flexbox流式布局一样，实现对齐到顶部、中间、底部，自由便利，只要在.media-body的父级加上align-self-start等属性。

<div class="media">
  <img class="align-self-start mr-3" src="..." alt="Generic placeholder image">
  <div class="media-body">
    <h5 class="mt-0">Top-aligned media</h5>
    <p>Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.</p>
    <p>Donec sed odio dui. Nullam quis risus eget urna mollis ornare vel eu leo. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus.</p>
  </div>
</div>

<div class="media">
  <img class="align-self-center mr-3" src="..." alt="Generic placeholder image">
  <div class="media-body">
    <h5 class="mt-0">Center-aligned media</h5>
    <p>Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.</p>
    <p class="mb-0">Donec sed odio dui. Nullam quis risus eget urna mollis ornare vel eu leo. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus.</p>
  </div>
</div>

<div class="media">
  <img class="align-self-end mr-3" src="..." alt="Generic placeholder image">
  <div class="media-body">
    <h5 class="mt-0">Bottom-aligned media</h5>
    <p>Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.</p>
    <p class="mb-0">Donec sed odio dui. Nullam quis risus eget urna mollis ornare vel eu leo. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus.</p>
  </div>
</div>

排序

通过修改HTML本身或通过添加一些自定义flexbox CSS来设置order属性（以您选择的整数）来更改媒体对象中内容的顺序。

<div class="media">
  <div class="media-body">
    <h5 class="mt-0 mb-1">Media object</h5>
    Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.
  </div>
  <img class="ml-3" src="..." alt="Generic placeholder image">
</div>

列表呈现

媒体对象的结构要求很少，您还可以在列表HTML元素上使用这些类，在<ul> or <ol>添加.list-unstyled从而删除浏览器默认列表样式，然后在li中添加.media元素块，也可以根据自己的需要进行间距调整。

<ul class="list-unstyled">
  <li class="media">
    <img class="mr-3" src="..." alt="Generic placeholder image">
    <div class="media-body">
      <h5 class="mt-0 mb-1">List-based media object</h5>
      Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.
    </div>
  </li>
  <li class="media my-4">
    <img class="mr-3" src="..." alt="Generic placeholder image">
    <div class="media-body">
      <h5 class="mt-0 mb-1">List-based media object</h5>
      Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.
    </div>
  </li>
  <li class="media">
    <img class="mr-3" src="..." alt="Generic placeholder image">
    <div class="media-body">
      <h5 class="mt-0 mb-1">List-based media object</h5>
      Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.
    </div>
  </li>
</ul>