day9:flex弹性盒子布局 20190910 - 学习

9日和10日两天学习了弹性盒子的属性及布局，采用了flex布局的元素被称为flex容器，也就是在css内声明了display:flex;属性的元素，简称为容器，而它的所有子元素是flex项目，简称项目，所有项目支持设置宽高。

容器具有6个属性，flex-direction(主轴方向)，flex-wrap(多个项目是否换行)，flex-flow(是前两个的简写方式)，justif-content(项目在主轴上的对齐方式)，align-items(项目在交叉轴上的对齐方式)，align-content(项目在多个交叉轴线上的对齐方式，只有一根时这个属性无效)。

项目也具有6个属性，order(定义项目排序，越小越靠前)，flex-grow(定义项目放大比例,默认不放大)，flex-shrink(项目的缩小比例，默认为1，缩小)，flex-basis(定义项目占据主轴的空间，默认为auto即原始大小，当设置了flex-basis时，设置的宽度失效)，flex(前面三个的缩写，默认为0 1 auot)，align-self(设置项目的对齐方式可以覆盖容器的align-items，默认值为auto)

实例

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <!--<link rel="stylesheet" href="css/common.css">-->
    <style>
        body,img,div,ul,li,p{border: 0;padding: 0;margin: 0}
        li{list-style: none}
        a{text-decoration: none}
        /*设置body的最大最小宽度，背景色等*/
        body{
            min-width: 320px;
            max-width: 768px;
            background-color: #edeff0;
            margin:0 auto;
            overflow-y: initial;
            position: relative;
            overflow-x: hidden;
            /*设置点击链接跳转时出现高亮,设置为透明: ios / ipad*/
            -webkit-tap-highlight-color: transparent;
        }
        /*设置顶部*/
        .top{
            width: 100%;
            min-width: 320px;
            max-width: 768px;
            background-color:#28292b ;
            height: 45px;
            position:fixed;
            left:50%;
            -webkit-transform: translateX(-50%);
            transform: translateX(-50%);
            display:flex;
            z-index: 9999;            
        }
        /*设置顶部第一种图片和最后一张图片*/
        .top img:first-of-type,.top img:last-of-type{
            width: 25px;
            height: 25px;
            margin-top: 8px;
            padding:0 10px;
        }
        .top img:first-of-type{
            border-radius: 50%;
        }
        /*设置logo图片*/
        .top .logo{
            flex-grow:1 ;
            text-align: center;

        }
        .top .logo img{
            width: 94px;
            height: auto;
            margin-top: auto;
        }
        /*轮播图片*/
        .slider img{
            width: 100%;
            height: 160px;
        }
        /*导航栏*/
        .nav {
            width: 100%;
            height: 170px;
            background-color: white;
            margin-top: 5px;
        }
        .nav .flex{
            padding: 6px;
            display: flex;
        }
        .nav .flex .item{
            height: 75px;
            /*flex:1;=flex:1 1 0;  flex是flex-grow,flex-shrink,flex-basis的简写，*/
            flex: 1 ;
            text-align: center;
        }
        .nav .flex li a{
            color: #2b2b2b;
            text-align: center;
        }
        .nav .flex li img{
            width: 45px;
            height: 45px;
        }

        /*推荐课程区*/
        h3{color:grey;}
        /*推荐课程区，图推荐*/
        .course{
            color:grey;
            height: 326px;
        }
        .course ul{
            display: flex;
        }
        .course ul li{
            padding: 3px;

        }
        .course ul li img {
            width:100%;
            height: 90px;
        }
        /*推荐课程区，图文推荐*/
        .course div{
            background-color: white;
            height: 90px;
            padding: 10px;
            margin: 10px 0;
            display: flex;
            justify-content: flex-start;
            box-shadow: 2px 2px 1px lightgray;
        }
        .course div a{
            flex:0.5;
            color:gray;
        }
        .course div img{
            width: 100%;
            height: 90px;
        }
        .course div p{
            flex:0.5;
            margin:10px 20px;
        }
        .course div p span:first-of-type{
            background-color: black;
            color: white;
            border-radius: 30%;
            padding: 1px 3px;
            font-size: 0.8rem;
        }
        .course div p span:last-of-type{
            font-size: 0.7rem;
        }
        /*最新课程区*/
        .update ul li {
            width: 100%;
            height: 94px;
            display: flex;
            background-color: white;
            margin: 10px 0;
            justify-content: flex-start;
            box-sizing: border-box;
            padding: 6px;
            box-shadow: 2px 2px 1px lightgray;
        }
        .update ul li a{
            flex:0.5;
            color:gray;
        }
        .update ul li a img{
            width:100%;
            height: 80px;
        }
        .update ul li div{
            flex:0.5;
            margin:10px 20px;
            /*限制div最大宽度，不限制的话，因为p元素的字符长度不一样就会导致，div盒子宽度不一样，本来是写在p元素上的，但是一想div下的a元素也可能撑大盒子*/
            max-width: 40%;
        }
        .update ul li div p:first-of-type{
            font-size: 0.7rem;
            width: 80%;
            height: 20px;
            line-height: 20px;
            overflow:hidden;
            white-space:nowrap;
            text-overflow:ellipsis;
            margin:5px 0  ;
            /*max-width:333px;  !*设置p段落的最大长度，否则会将弹性盒子的项目撑大*!*/
        }
        .update ul li div p:last-of-type{
            position: relative;
            width: 90%;
            height: 20px;
            font-size: 0.7rem;
            padding-left: 10px;
            padding-top: 3px;

        }
        .update ul li div p:last-of-type span:first-of-type{
            border-radius:30% ;
            background-color: #2b2b2b;
            color: white;
            padding: 0 3px;
        }
        /*使用绝对定位将播放次数放到右边*/
        .update ul li div p:last-of-type span:last-of-type{
            position: absolute;
            right:10px;
        }
        /*最新文章*/
        .article ul li{
            width: 100%;
            height: 90px;
            background-color: white;
            display:flex;
            align-items:center;
            justify-content: space-around;
            margin:10px 0;
            box-shadow: 2px 2px 1px lightgray;
        }
        .article ul li a{
            color:gray;
        }
        .article ul li a:first-of-type{
            flex:0.65;
            margin-bottom: 20px;
            margin-left: 20px;
            max-width: 70%;
        }
        h4{
            white-space: nowrap;
            overflow: hidden;
            max-width: 90%;
        }
        .article ul li a:first-of-type p{
            margin-top:-10px ;
            font-size: 0.8rem;
        }
        .article ul li a:last-of-type{
            flex:0.35;
            margin-right: 20px;
        }
        .article ul li a:last-of-type img{
            width: 100%;
            height: 65px;
        }
        /*查看更多通用*/
        .more{
            display: block;
            width: 100%;
            height: 40px;
            background-color: white;
            margin:0 auto;
            text-align: center;
            line-height: 40px;
            color: gray;
            box-shadow: 2px 2px 1px lightgray;
        }
        /*最新问答*/
        .question li a{
            margin-left:15px ;
            font-size: 1.2rem ;
            color:gray;
        }
        .question li{
            width: 100%;
            height: 50px;
            background-color: white;
            margin: 10px 0;
            line-height: 50px;
            position: relative;
            box-shadow: 2px 2px 1px lightgray;
        }
        .question li span{
            position: absolute;
            right: 30px;
            color:gray;
            font-size: 0.9rem;
        }
        /*底部导航区*/
        .footer{
            background-color: #edeff0;
            width: 100%;
            min-width: 320px;
            max-width: 768px;
            position: fixed;
            bottom:0;
            height: 45px;
            left:50%;
            -webkit-transform: translateX(-50%);
            transform: translateX(-50%);
            border-top: #2b2b2b 1px solid;
        }
        .footer a{
            color:grey;
        }
        .footer ul{
            display: flex;
            text-align: center;
        }
        .footer ul li{
            text-align: center;
            margin-top: 2px;
            flex: 1;
        }
        .footer ul li img{
            width: 18px;
            height: 18px;
        }</style>
    <title>php中文网-教程_手册_视频-免费php在线学习平台</title>
</head>
<body>
    <!--顶部栏，使用固定定位，定位在顶部，跟随滚动条-->
    <div class="top">
        <img src="image/user-pic.jpeg" alt="">
        <div class="logo">
            <img src="image/logo.png" alt="">
        </div>
        <img src="image/user-nav.jpg" alt="">
    </div>
    <!--轮播图，图片代替-->
    <div class="slider">
        <img src="image/banner.jpg" alt="">
    </div>
    <!--导航区，使用两个flex布局-->
    <div class="nav">
        <ul class="flex">
            <li class="item"><a href=""><img src="image/html.png" alt=""><br>HTML/CSS</a></li>
            <li class="item"><a href=""><img src="image/JavaScript.png" alt=""><br>JavaScript</a></li>
            <li class="item"><a href=""><img src="image/code.png" alt=""><br>服务端</a></li>
            <li class="item"><a href=""><img src="image/sql.png" alt=""><br>数据库</a></li>
        </ul>
        <ul class="flex">
            <li class="item"><a href=""><img src="image/app.png" alt=""><br>移动端</a></li>
            <li class="item"><a href=""><img src="image/manual.png" alt=""><br>手册</a></li>
            <li class="item"><a href=""><img src="image/tool2.png" alt=""><br>工具</a></li>
            <li class="item"><a href=""><img src="image/live.png" alt=""><br>直播</a></li>
        </ul>
    </div>
    <!--推荐课程区-->
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    <div class="course">
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        <div>
            <a href=""><img src="image/tjkc3.jpg" alt=""></a>
            <p>
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    <h3>最新更新</h3>
    <div class="update">
        <ul>
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            <!--***，懂了，我还以为是图片的问题，结果是div下的p段落字符长度不一样导致的，所以设置了一个div p:first-of-type的最大长度解决问题-->
            <li>
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            </li>
        </ul>
    </div>
    <!--最新文章-->
    <h3>最新文章</h3>
    <div class="article">
        <ul>
            <li>
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            </li>
        </ul>
        <a href="" class="more">查看更多</a>
    </div>
    <!--最新问答-->
    <h3>最新问答</h3>
    <div class="question">
        <ul>
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    </div>
    <div style="width: 100%;height: 80px"><!--为了防止底部导航条遮挡内容--></div>
    <!--底部固定导航-->
    <div class="footer">
        <ul>
            <li><a href=""><img src="image/zhuye.png" alt=""><br><span>首页</span></a></li>
            <li><a href=""><img src="image/video.png" alt=""><br><span>视频</span></a></li>
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            <li><a href=""><img src="image/geren.png" alt=""><br><span>我的</span></a></li>
        </ul>
    </div>
</body>
</html>

运行实例 »

点击 "运行实例" 按钮查看在线实例

总结：写的太慢了，来不及写其他的，上班时间偷偷摸摸的写！经过测试发现好像项目也可以做为flex容器来嵌套，二写的时候遇到了一个大坑浪费了一些时间，在写最新更新的时候因为p标签内的字符太长会影响项目的长度，我一度以为是图片的影响，但图片宽度又限制的，所以在这卡了很久！后来才发现是p元素内字符太长的影响，所以给它的父元素div增加了一个max-width的相对宽度，解决问题！！

Correction status：qualified

Teacher's comments：发现问题, 再通过自己思考找到答案, 这个方法相当正确 , 这回你终生难忘

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