006_CSS中重要概念之布局相关(下)-优快云博客

本文链接：https://blog.youkuaiyun.com/w_wangewanbuhuidege/article/details/114559763

本文介绍了使用CSS实现三栏布局的方法，包括浮动和定位两种方式，并探讨了水平垂直居中的解决方案。同时，还讲解了如何创建块级格式化上下文(BFC)来解决页面布局中的常见问题。

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001_三栏布局(h3)

源代码

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>三栏布局</title>
  <style>
    .wrapper {
      margin-bottom: 20px;
    }
    .left, .middle, .right {
      height: 400px;
    }
    .left, .right {
      width: 200px;
      background-color: red;
      float: left;
    }
    .float .right {
      float: right;
    }
    .float .middle {
      background-color: blue;
      margin: 0 200px;
    }
    .absolute {
      position: relative;
      height: 400px;
    }
    .absolute .left {
      position: absolute;
      left: 0;
      background-color: red;
    }
    .absolute .middle {
      position: absolute;
      left: 200px;
      right: 200px;
      background-color: blue;
    }
    .absolute .right {
      position: absolute;
      right: 0;
      background-color: red;
    }
  </style>
</head>
<body>
  <h1>三栏布局</h1>
  <div class="wrapper float">
    <h2>浮动实现</h2>
    <div class="left"></div>
    <div class="right"></div>
    <div class="middle"></div>
  </div>
  <div class="wrapper absolute">
    <h2>定位实现实现</h2>
    <div class="left"></div>
    <div class="right"></div>
    <div class="middle"></div>
  </div>
</body>
</html>

浏览器界面

002_水平垂直居中(h3)

源代码

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>水平垂直居中</title>
    <style>
      .box {
        width: 200px;
        height: 200px;
        background-color: red;
        margin-bottom: 20px;
      }
      .box1 {
        text-align: center;
        line-height: 200px;
      }
      .box1 span {
        background-color: blue;
      }
      .inner-box {
        width: 50px;
        height: 50px;
        background-color: blue;
        position: absolute;
        top: 50%;
        margin-top: -25px;
        left: 50%;
        margin-left: -25px;
      }
      .box2 {
        position: relative;
      }
      .inner-box2 {
        background-color: blue;
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%);
      }
      .box3 {
        position: relative;
      }
    </style>
  </head>
  <body>
    <h1>水平垂直居中</h1>
    <div class="box box1">
      <span>行内元素</span>
    </div>
    <div class="box box2">
      <div class="inner-box">块级元素</div>
    </div>
    <div class="box box3">
      <div class="inner-box2">块级元素</div>
    </div>
  </body>
</html>

浏览器界面

003_BFC块级格式化上下文(h3)

源代码

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>BFC块级格式化上下文</title>
    <style>
      .box {
        background-color: red;
        border: 1px solid #000;
        width: 600px;
        overflow: hidden;
      }
      .float-box {
        float: left;
        height: 100px;
        width: 100px;
        border: 1px solid #000;
      }
      p {
        width: 600px;
        background-color: blue;
      }
      .first {
        margin-bottom: 30px;
      }
      .second {
        margin-top: 20px;
      }
      .margin-box {
        overflow: hidden;
      }
    </style>
  </head>
  <body>
    <div class="box">
      <div class="float-box">it is float-box</div>
      <div class="normal-box">it is normal-box</div>
    </div>
    <!-- 边距塌陷问题 -->
    <div>
      <div class="margin-box">
        <p class="first">123</p>
      </div>
      <p class="second">456</p>
    </div>
  </body>
</html>

浏览器界面