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  • css--float浮动

    前戏

    前面我们学习了CSS相关的知识，现在试想一下，如果我们想把两个div放在一行显示，该怎么处理？前面也说过，div是块级标签，默认占一行，这时候如果想要达成效果，那就要用到float了

    float

    float中的四个参数

    float：left      左浮动

float：right     右浮动

float：none      不浮动

float：inherit   继承

    先来看一下不加float的效果

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
         *{padding: 0;margin: 0}
        div{height:100px;width:100px;background: red}
     </style>
</head>
<body>
        <div>1</div>
        <div>2</div>
</body>
</html>
    left
    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
         *{padding: 0;margin: 0}
        div{height:100px;width:100px;background: red;
            text-align: center;
         line-height: 100px;}

         div{float: left;
            margin-right: 10px;
         }

     </style>
</head>
<body>
        <div class="c1">1</div>
        <div class="c2">2</div>
</body>
</html>
    right
    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
         *{padding: 0;margin: 0}
        div{height:100px;width:100px;background: red;
            text-align: center;
         line-height: 100px;}

         div{float: right;
            margin-right: 10px;
         }

     </style>
</head>
<body>
        <div class="c1">1</div>
        <div class="c2">2</div>
</body>
</html>

    注意：float：right时，两个div的顺序就反过来了，因为先把c1的浮动到最右边，然后浮动c2

    none
    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
         *{padding: 0;margin: 0}
        div{height:100px;width:100px;background: red;
            text-align: center;
         line-height: 100px;}

         div{float: none;
            margin-right: 10px;
         }

     </style>
</head>
<body>
        <div class="c1">1</div>
        <div class="c2">2</div>
</body>
</html>

    none就是不浮动，就和默认的div一样的效果

    inherit
    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
         *{padding: 0;margin: 0}
        div{height:100px;width:100px;background: red;
            text-align: center;
         line-height: 100px;}

         .test{float: right;
            height: 200px;width: 200px;background: green;
         }
         .c1,.c2{
             float: inherit;
            margin-top:10px; }

     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
    </div>
</body>
</html>

    代码解释：

    我们给class为c1和c2的加上了float: inherit;给它的父元素加上了float: right，所以父元素会像右浮动，但是因为c1和c2继承了父元素的浮动，所以也会像右浮动，解释完毕。

    float的副作用

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;margin-right: 10px}
            .c3{background: green;height: 100px;width: 100px;}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
        <div class="c3"></div>

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

    我们可以看到，上面绿色的框产生了易位，原本是要想绿色的框在红色的下面显示，这就是浮动的副作用之一

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;}
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
            .c3{background: green;height: 100px;width: 100px;}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
<!--        <div class="c3"></div>-->

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

    如果我们给上面的代码没有添加float，则子元素会把父元素的高度撑起来，加上float之后，父元素的高度就成了一条线。这也是float的副作用

    清除浮动的副作用

    清除浮动的副作用有四种方法

    1. 手动给父元素设置高度

    2.通过clear清除内部和外部浮动

    3.给父元素添加overfloat属性并结合zoom：1使用

    4.给父元素添加浮动

     手动给父元素设置高度

    我们先来看一下副作用

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;width:100px;}
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>

    </div>
</body>
</html>
    View Code

    给父元素设置高度height：30px；

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                height:30px; }
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>

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

    但是我们想一想，如果子标签有多个，是不是就超过了父元素的高度呢？

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                height:30px; }
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>

    </div>
</body>
</html>
    View Code

    经常测试，发现真是这样的，那我们使用添加overfloat属性并结合zoom来试一下，看能不能解决掉我们的问题

    overflow
    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                overflow: hidden;
                zoom: 1}
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>

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

    解释：overflow是将溢出的截取掉

    经过测试发现，完美的解决了我们的问题

    通过clear清除内部和外部浮动

    clear有四个属性

    clear：none
clear：left    左边不允许有浮动
clear：right   右边不允许有浮动
clear：both    左右都不允许有浮动

    先来看一下副作用的效果

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                height:100px; }
            .c1{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
            .c2{background: green;height:50px;width:30px;}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>


    </div>
</body>
</html>
    View Code

    使用clear：left解决副作用

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                height:100px; }
            .c1{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
            .c2{background: green;height:50px;width:30px;
                clear: left;
            }
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>


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

    其余的三个也是同理，就不做具体的演示

    给父元素添加浮动

    还是先看一下副作用的效果

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                }
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>

    </div>
</body>
</html>
    View Code

    我们给父元素也加上浮动float：left

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                float: left;
                }
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>

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

    刷新之后，也能解决我们的问题，那给父元素添加一个兄弟元素看看效果

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                float: left;
                }
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
            .c3{height: 100px;width: 100px;background: #4d4d4d}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>

    </div>
    <div class="c3">啦啦</div>
</body>
</html>

    刷新之后发现，虽然父元素的问题解决了，但是它的兄弟标签有嵌入到了里面，我们可以给兄弟标签加上clear：both解决

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
            .test{border: 1px solid red;
                width:100px;
                float: left;
                }
            .c1,.c2{background: red;float: left;height: 30px;width: 20px;
                margin-right: 10px}
            .c3{height: 100px;width: 100px;background: #4d4d4d;
            clear: both}
     </style>
</head>
<body>
    <div class="test">
        <div class="c1">1</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>
        <div class="c2">2</div>

    </div>
    <div class="c3">啦啦</div>
</body>
</html>
    点我偷看

    小练习

    使用浮动完成以下效果

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
     <style>
         *{padding: 0;margin: 0;}
         .test{background: #ccc;height: 32px;width: 700px;}
         .c2{float: left;margin-right:30px;line-height: 32px;}
         .icon{float: right}
         .d1{float: inherit;margin-left: 30px;line-height: 32px;}

     </style>
</head>
<body>
    <div class="test">
        <div class="a1">
            <div class="c2">测试</div>
            <div class="c2">开发</div>
            <div class="c2">产品</div>
            <div class="c2">UI</div>
        </div>

        <div class="icon">
            <div class="d1">python</div>
            <div class="d1">HTML</div>
            <div class="d1">CSS</div>
            <div class="d1">Js</div>
        </div>
    </div>

</body>
</html>
    点我偷看
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  • 原文地址：https://www.cnblogs.com/zouzou-busy/p/11042366.html
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