基础语法

/*
    CSS注释
*/

CSS样式

CSS应用方式

内联式

在标签上写样式

<img src="..." style="height:100px" />

<div style="color:red;">中国联通</div>

嵌入式

在head标签中写style标签

外联式

样式写到文件中，放到static目录下的css文件，class='c1'，c1是css文件中的变量名

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="common.css" />
</head>
<body>

<h1 class='c1'>用户登录</h1>
<h1 class='c2'>用户登录</h1>
<h1 class='c2'>用户登录</h1>
<h1 class='c1'>用户登录</h1>
    
</body>
</html>

选择器

id选择器

id标准写法是id唯一性，所以不太常用

类选择器

标签选择器

所有的标签统一设置属性

属性选择器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .yy [type="text"]{
      color: pink;
  }
        .yy [name = 'amer']{
      color: rebeccapurple;
  }
    </style>
</head>
<body>
      <div class="yy">
        <input type="text">
        <input type="password">
      <ul>
          <li name = 'amer'>美国</li>
          <li>日本</li>
          <li>韩国</li>
      </ul>
  </div>
</body>
</html>

后代选择器

找儿子 .类名>儿子标签名

找所有后代 .类名>标签名

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .yy li{
      color: pink;
  }
        .yy > a{
      color: dodgerblue;
  }
    </style>
</head>
<body>
      <div class="yy">
          <a>百度</a>
      <div>
          <a>谷歌</a>
      </div>
      <ul>
          <li>美国</li>
          <li>日本</li>
          <li>韩国</li>
      </ul>
  </div>
</body>
</html>

3.3 样式覆盖逻辑

3.3.1 无重复全部应用。重复内容按照头部顺序覆盖，和标签内顺序无关。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            color: red;
            border: 1px solid red;
        }
        .c2{
            font-size: 28px;
            color: green;
        }
    </style>
</head>
<body>
    <div class="c2 c1">中国联通</div>
</body>
</html>

3.3.2 声明不要覆盖样式

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            color: red !important;
            border: 1px solid red;
        }
        .c2{
            font-size: 28px;
            color: green;
        }
    </style>
</head>
<body>
    <div class="c2 c1">中国联通</div>
</body>
</html>

3.4 背景覆盖无死角

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body {
            margin: 0;
        }
    </style>
</head>
<body>
    <div style="background-color: green">1</div>
</body>
</html>

3.5 hover样式(伪类，冒号后边追加的)

3.5.1 hover正常应用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            height: 59px;
            width: 300px;
            border: 1px solid red;
            margin: 0 auto;
            background-color: gold;
        }
        .c1:hover{
            background-color: green;
        }
    </style>
</head>
<body>
    <div class="c1"></div>
</body>
</html>

3.5.2 hover升级应用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1 {
            color: red;
            font-size: 18px;
        }

        .c1:hover {
            color: green;
            font-size: 50px;
        }

        .c2 {
            height: 300px;
            width: 500px;
            border: 3px solid red;
        }

        .c2:hover {
            border: 3px solid green;
        }

        .download {
            display: none;
        }

        .app:hover .download {
            display: block;
        }
        .app:hover .title{
            color: red;
        }
    </style>
</head>
<body>
<div class="c1">联通</div>
<div class="c2">广西</div>

<div class="app">
    <div class="title">下载APP</div>
    <div class="download">
        <img src="images/qcode.png" alt="">
    </div>
</div>

</body>
</html>

3.6 显示/隐藏

显示 display: none;

隐藏display: block;

3.7 after追加(伪类)

相当于后置处理追加内容
只对追加的内容设置属性

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1:after{
            content: '追加的内容';
            font-size: 100px;
            background-color: green;
        }
    </style>
</head>
<body>
    <div class="c1">吴阳军</div>
    <div class="c1">梁吉宁</div>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1:after{
            content: '追加的内容';
            font-size: 50px;
            background-color: green;
            clear: both;
        }
        .c1{
            float: right;
        }
    </style>
</head>
<body>
    <div>
        <div class="c1">吴阳军</div>
        <div class="c1">梁吉宁</div>
        <div class="c1">梁吉宁</div>
    </div>
</body>
</html>

4 块级标签和行内标签

4.1 宽高

宽高可以设置百分比

块级标签：默认有效（霸道，右侧区域空白，也不给你占用），div

行内标签：默认无效，span

4.2 综合块级行级属性

display: inline-block

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            display: inline-block;
            height: 100px;
            width: 300px;
            border: 1px solid red;
        }
    </style>
</head>
<body>
    <span class="c1">中国</span>
    <span class="c1">联通</span>
    <span class="c1">联通</span>
    <span class="c1">联通</span>
</body>
</html>

5 文字设置

5.1 文字基本设置

大小
```
font-size: 58px;
```
颜色
```
color: #00FF7F;
```
字体
```
font-family: Microsoft Yahei;
```

加粗

font-weight: 50;

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            display: inline-block;
            color: #00FF7F;
            font-size: 58px;
            font-weight: 50;
            font-family: Microsoft Yahei;
        }
    </style>
</head>
<body>
    <div class="c1">中国联通</div>
    <div>中国移动</div>
</body>
</html>

5.2 文字对齐方式

水平方向居中 text-align: center;

垂直方向居中 line-height: 59px; 文本框对应高度

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            height: 59px;
            width: 300px;
            border: 1px solid red;
            text-align: center; /* 水平方向居中 */
            line-height: 59px; /* 垂直方向居中 */
        }
    </style>
</head>
<body>
    <div class="c1">智利</div>
</body>
</html>

6 浮动模式

6.1 行内标签浮动

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div>
        <span>左边</span>
        <span style="float: right">右边</span>
    </div>
</body>
</html>

6.2 块级标签浮动

脱离了父类，无法撑起来父类，需要增加

<div style="clear: both;"></div>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .item{
            float: left;
            width: 280px;
            height: 170px;
            border: 1px solid red;
        }
    </style>
</head>
<body>
    <div style="background-color: dodgerblue">
        <div class="item">第一个</div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div class="item"></div>
        <div style="clear: both;"></div>
    </div>
    <div>你哦啊呀</div>
</body>
</html>

7 内边距

内边距，我自己内部设置一点距离。

上下左右为统一值，则为：padding: 20px;

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .outer {
            border: 1px solid red;
            height: 200px;
            width: 200px;
            padding-top: 20px;
            padding-left: 20px;
            padding-right: 20px;
            padding-bottom: 20px;
        }
    </style>
</head>
<body>
<div class="outer">
    <div style="background-color: gold;">听妈妈的话</div>
    <div>小朋友</div>
    <span>行内</span>
</div>
</body>
</html>

8 外边距

外边距，我与别人加点距离。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            margin-top:20px;
            background-color: gold;
            height: 100px;
        }
    </style>
</head>
<body>
    <div class="c1" ></div>
    <div class="c1" ></div>
</body>
</html>

9 区域居中

margin: 0 auto;

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            height: 59px;
            width: 300px;
            border: 1px solid red;
            margin: 0 auto;
            background-color: gold;
        }
        .c2{
            height: 30px;
            width: 50px;
            border: 1px solid red;
            margin: 0 auto;
            background-color: green;
        }
    </style>
</head>
<body>
    <div class="c1">
        <div class="c2"></div>
    </div>
</body>
</html>

10 透明度

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body {
            margin: 0;
        }
        .c1{
            background-color: green;
            opacity: 0.5;
        }
        .c1:hover{
            opacity: 1;
        }
    </style>
</head>
<body>
    <div class="c1">你好</div>
 </body>
</html>

11 position 定位/位置

11.1 fixed

11.1.1 永远在窗口的右下角

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            width: 150px;
            height: 50px;
            border: 1px solid red;
            
            position: fixed;
            right: 100px;
            bottom:100px;
        }
    </style>
</head>
<body>
    <div>
        <div class="c1">吴阳军</div>
    </div>
</body>
</html>

11.1.2 居中设置

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            width: 150px;
            height: 50px;
            border: 1px solid red;

            position: fixed;
            right: 0;
            left: 0;
            margin: auto;
        }
    </style>
</head>
<body>
    <div>
        <div class="c1">吴阳军</div>
    </div>
</body>
</html>

11.1.3 全屏覆盖

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            background-color: bisque;
            position: fixed;
            right: 0;
            left: 0;
            top: 0;
            bottom: 0;
            margin: auto;
        }
    </style>
</head>
<body>
    <div>
        <div class="c1"></div>
    </div>
</body>
</html>

11.2 relative + absolute

relative 相当于参照物

absolute 相当于移动物

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            width: 500px;
            height: 100px;
            border: 1px solid red;
            position: relative;
        }
        .c1 .c2{
            width: 110px;
            height: 50px;
            background-color: green;
            position: absolute;
            right: 0;
            bottom: 0;
        }
    </style>
</head>
<body>
    <div>
        <div class="c1">
            <div class="c2">

            </div>
        </div>
    </div>
</body>
</html>