ZhangYang's Blog

flex布局

发表于 | 分类于
  • Flex 是 Flexible Box 的缩写，意为”弹性布局”
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// 任何一个容器都可以指定为 Flex 布局
.box{
  display: flex;
}
// 行内元素也可以使用 Flex 布局
.box{
  display: inline-flex;
}
  • 设为 Flex 布局以后，子元素的float、clear和vertical-align属性将失效

基本概念

  • 设置 Flex 布局的元素，称为 Flex 容器（flex container），简称”容器”
  • 所有子元素自动成为容器成员，称为 Flex 项目（flex item），简称”项目”
  • 容器默认存在两根轴：水平的主轴（main axis）和垂直的交叉轴（cross axis）
  • 主轴的开始位置（与边框的交叉点）叫做main start，结束位置叫做main end
  • 交叉轴的开始位置叫做cross start，结束位置叫做cross end
  • 项目默认沿主轴排列。单个项目占据的主轴空间叫做main size，占据的交叉轴空间叫做cross size

image

容器的属性

  • flex-direction
  • flex-wrap
  • flex-flow(不常用)
  • justify-content
  • align-items
  • align-content(不常用)

flex-direction

  • flex-direction属性决定主轴的方向（即项目的排列方向）
  • .box { flex-direction: row | row-reverse | column | column-reverse; }
  • row（默认值）：主轴为水平方向，起点在左端
  • row-reverse：主轴为水平方向，起点在右端
  • column：主轴为垂直方向，起点在上沿
  • column-reverse：主轴为垂直方向，起点在下沿

image

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #E2E2E2;
      max-width: 1024px;
      color: #595B66;
    }
    .box {
      background-color: white;
      margin: 0 0 55px;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      vertical-align: middle;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-1 {
      flex-direction: row;
    }
  </style>
</head>
<body>
  <div class="box box-1">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
  </div>
</body>
</html>

image

flex-wrap

  • 默认情况下，项目都排在一条线（又称”轴线”）上;flex-wrap属性定义，如果一条轴线排不下，如何换行
  • .box{ flex-wrap: nowrap | wrap | wrap-reverse; }

image

  • nowrap（默认）：不换行
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    <!DOCTYPE html>
    <html lang="en">
    <head>
      <meta charset="UTF-8">
      <title>Document</title>
      <style>
        body {
          padding: 20px;
          margin: 0 auto;
          background-color: #ccc;
          max-width: 1024px;
        }
        .box {
          background-color: white;
          display: flex;
        }
        .box-item {
          width: 200px;
          height: 200px;
          line-height: 200px;
          margin: 5px;
          background-color: #ffd200;
          font-size: 100px;
          color: white;
          text-align: center;
        }
        .box-2 {
          flex-direction: row;
          flex-wrap: nowrap;
        }
      </style>
    </head>
    <body>
      <div class="box box-2">
        <div class="box-item">1</div>
        <div class="box-item">2</div>
        <div class="box-item">3</div>
        <div class="box-item">4</div>
        <div class="box-item">5</div>
        <div class="box-item">6</div>
        <div class="box-item">7</div>
      </div>
    </body>
    </html>

image

  • wrap：换行，第一行在上方
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-3 {
      flex-direction: row;
      flex-wrap: wrap;
    }
  </style>
</head>
<body>
  <div class="box box-3">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
  </div>
</body>
</html>

image

  • wrap-reverse：换行，第一行在下方
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-4 {
      flex-direction: row;
      flex-wrap: wrap-reverse;
    }
  </style>
</head>
<body>
  <div class="box box-4">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
  </div>
</body>
</html>

image

flex-flow

  • flex-flow属性是flex-direction属性和flex-wrap属性的简写形式，默认值为row nowrap
  • .box { flex-flow: || ; }
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-5 {
      flex-direction: row;
      flex-flow: row nowrap;
    }
  </style>
</head>
<body>
  <div class="box box-5">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
  </div>
</body>
</html>

image

justify-content

  • justify-content属性定义了项目在主轴上的对齐方式
  • .box { justify-content: flex-start | flex-end | center | space-between | space-around; }
  • flex-start（默认值）：左对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-6 {
      justify-content: flex-start;
    }
  </style>
</head>
<body>
  <div class="box box-6">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
  </div>
</body>
</html>

image

  • flex-end：右对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-7 {
      justify-content: flex-end;
    }
  </style>
</head>
<body>
  <div class="box box-7">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
  </div>
</body>
</html>

image

  • center: 居中
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-8 {
      justify-content: center;
    }
  </style>
</head>
<body>
  <div class="box box-8">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
  </div>
</body>
</html>

image

  • space-between：两端对齐，项目之间的间隔都相等
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-9 {
      justify-content: space-between;
    }
  </style>
</head>
<body>
  <div class="box box-9">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
  </div>
</body>
</html>

image

  • space-around：每个项目两侧的间隔相等。所以，项目之间的间隔比项目与边框的间隔大一倍
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-10 {
      justify-content: space-around;
    }
  </style>
</head>
<body>
  <div class="box box-10">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
  </div>
</body>
</html>

image

align-items

  • align-items属性定义项目在交叉轴上如何对齐
  • .box { align-items: flex-start | flex-end | center | baseline | stretch; }
  • flex-start：左对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-11 {
      align-items: flex-start;
    }
    .item-tall {
      height: 400px;
      line-height: 400px;
    }
  </style>
</head>
<body>
  <div class="box box-11">
    <div class="box-item">1</div>
    <div class="box-item item-tall">2</div>
    <div class="box-item">3</div>
    <div class="box-item item-tall">4</div>
  </div>
</body>
</html>

image

  • flex-end：交叉轴的终点对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-12 {
      align-items: flex-end;
    }
    .item-tall {
      height: 400px;
      line-height: 400px;
    }
  </style>
</head>
<body>
  <div class="box box-12">
    <div class="box-item">1</div>
    <div class="box-item item-tall">2</div>
    <div class="box-item">3</div>
    <div class="box-item item-tall">4</div>
  </div>
</body>
</html>

image

  • center：交叉轴的中点对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-13 {
      align-items: center;
    }
    .item-tall {
      height: 400px;
      line-height: 400px;
    }
  </style>
</head>
<body>
  <div class="box box-13">
    <div class="box-item">1</div>
    <div class="box-item item-tall">2</div>
    <div class="box-item">3</div>
    <div class="box-item item-tall">4</div>
  </div>
</body>
</html>

image

  • baseline: 项目的第一行文字的基线对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-14 {
      align-items: baseline;
    }
    .box-14 .box-item{
      font-size: 88px;
      line-height: initial;
      text-decoration: underline;
    }
    .item-tall {
      height: 400px;
      line-height: 400px;
    }
    .box-14 .item-tall{
      font-size: 122px;
      line-height: initial;
    }
  </style>
</head>
<body>
  <div class="box box-14">
    <div class="box-item">1</div>
    <div class="box-item item-tall">2</div>
    <div class="box-item">3</div>
    <div class="box-item item-tall">4</div>
  </div>
</body>
</html>

image

  • stretch（默认值）：如果项目未设置高度或设为auto，将占满整个容器的高度
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 200px;
      height: 200px;
      line-height: 200px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-15 {
      align-items: stretch;
    }
    .box-15 .box-item {
      height: auto;
    }
    .item-tall {
      height: 400px;
      line-height: 400px;
    }
  </style>
</head>
<body>
  <div class="box box-15">
    <div class="box-item">1</div>
    <div class="box-item item-tall">2</div>
    <div class="box-item">3</div>
    <div class="box-item item-tall">4</div>
  </div>
</body>
</html>

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align-content

  • align-content属性定义了多根轴线（多行）的对齐方式。如果项目只有一根轴线，该属性不起作用
  • .box { align-content: flex-start | flex-end | center | space-between | space-around | stretch; }
  • flex-start：交叉轴的起点对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-16 {
      flex-wrap: wrap;
      align-content: flex-start;
    }
    .box-tall {
      height: 500px;
    }
  </style>
</head>
<body>
  <div class="box box-tall box-16">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
    <div class="box-item">8</div>
    <div class="box-item">9</div>
  </div>
</body>
</html>

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  • flex-end：与交叉轴的终点对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-17 {
      flex-wrap: wrap;
      align-content: flex-end;
    }
    .box-tall {
      height: 500px;
    }
  </style>
</head>
<body>
  <div class="box box-tall box-17">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
    <div class="box-item">8</div>
    <div class="box-item">9</div>
  </div>
</body>
</html>

image

  • center：与交叉轴的中点对齐
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-18 {
      flex-wrap: wrap;
      align-content: center;
    }
    .box-tall {
      height: 500px;
    }
  </style>
</head>
<body>
  <div class="box box-tall box-18">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
    <div class="box-item">8</div>
    <div class="box-item">9</div>
  </div>
</body>
</html>

image

  • space-between：与交叉轴两端对齐，轴线之间的间隔平均分布
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-19 {
      flex-wrap: wrap;
      align-content: space-between;
    }
    .box-tall {
      height: 500px;
    }
  </style>
</head>
<body>
  <div class="box box-tall box-19">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
    <div class="box-item">8</div>
    <div class="box-item">9</div>
  </div>
</body>
</html>

image

  • space-around：每根轴线两侧的间隔都相等。所以，轴线之间的间隔比轴线与边框的间隔大一倍
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-20 {
      flex-wrap: wrap;
      align-content: space-around;
    }
    .box-tall {
      height: 500px;
    }
  </style>
</head>
<body>
  <div class="box box-tall box-20">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
    <div class="box-item">8</div>
    <div class="box-item">9</div>
  </div>
</body>
</html>

image

  • stretch（默认值）：轴线占满整个交叉轴
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-21 {
      flex-wrap: wrap;
      align-content: stretch;
    }
    .box-21 .box-item {
      height: auto;
    }
    .box-tall {
      height: 500px;
    }
  </style>
</head>
<body>
  <div class="box box-tall box-21">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item">4</div>
    <div class="box-item">5</div>
    <div class="box-item">6</div>
    <div class="box-item">7</div>
    <div class="box-item">8</div>
    <div class="box-item">9</div>
  </div>
</body>
</html>

image

项目的属性

  • order(代替双飞翼)
  • flex-grow
  • flex-shrink(不常用)
  • flex-basis(不常用)
  • flex
  • align-self

order

  • order属性定义项目的排列顺序。数值越小，排列越靠前，默认为0
  • .item { order: ; }
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-item div{
      font-size: 14px;
      position: relative;
      top: -100px;
    }
    .box-22 .order {
      order: -1;
    }
  </style>
</head>
<body>
  <div class="box box-22">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
    <div class="box-item order">4<div>(order:-1)</div></div>
  </div>
</body>
</html>

image

flex-grow

  • flex-grow属性定义项目的放大比例，默认为0，即如果存在剩余空间，也不放大
  • 如果所有项目的flex-grow属性都为1，则它们将等分剩余空间（如果有的话）;如果一个项目的flex-grow属性为2，其他项目都为1，则前者占据的剩余空间将比其他项多一倍
  • .item { flex-grow: ; / default 0 / }
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-item div{
      font-size: 14px;
      position: relative;
      top: -100px;
    }
    .box-23 .box-item{
      flex-grow: 1;
    }
    .box-23 .grow-2 {
      flex-grow: 2;
    }
  </style>
</head>
<body>
  <div class="box box-23">
    <div class="box-item grow">1 <div>flex-grow: 1</div></div>
    <div class="box-item grow grow-2">2 <div>flex-grow: 2</div></div>
    <div class="box-item grow">3 <div>flex-grow: 1</div></div>
  </div>
</body>
</html>

image

flex-shrink

  • flex-shrink属性定义了项目的缩小比例，默认为1，即如果空间不足，该项目将缩小
  • 如果所有项目的flex-shrink属性都为1，当空间不足时，都将等比例缩小。如果一个项目的flex-shrink属性为0，其他项目都为1，则空间不足时，前者不缩小
  • 负值对该属性无效
  • .item { flex-shrink: ; / default 1 / }
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-item div{
      font-size: 14px;
      position: relative;
      top: -100px;
    }
    .box-24 .box-item {
      width: 400px;
    }
    .box-24 .shrink{
      flex-shrink: 0;
    }
  </style>
</head>
<body>
  <div class="box box-24">
    <div class="box-item shrink">1 <div>flex-shrink: 0</div></div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
  </div>
</body>
</html>

image

flex-basis属性

  • flex-basis属性定义了在分配多余空间之前，项目占据的主轴空间(main size)
  • 浏览器根据这个属性，计算主轴是否有多余空间。它的默认值为auto，即项目的本来大小
  • .item { flex-basis: ; | auto; / default auto / }
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-25 .box-item {
      flex-basis: 200px;
      width: 400px; // width 将失去作用
    }
  </style>
</head>
<body>
  <div class="box box-25">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item">3</div>
  </div>
</body>
</html>

image

flex属性

  • flex属性是flex-grow, flex-shrink 和 flex-basis的简写，默认值为0 1 auto。后两个属性可选
  • 该属性有两个快捷值：auto (1 1 auto) 和 none (0 0 auto)
  • .item { flex: none | [ <’flex-grow’> <’flex-shrink’>? || <’flex-basis’> ] }

align-self属性

  • align-self属性允许单个项目有与其他项目不一样的对齐方式，可覆盖align-items属性。默认值为auto，表示继承父元素的align-items属性，如果没有父元素，则等同于stretch
  • .item { align-self: auto | flex-start | flex-end | center | baseline | stretch; }
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
      margin: 0 auto;
      background-color: #ccc;
      max-width: 1024px;
    }
    .box {
      background-color: white;
      display: flex;
    }
    .box-item {
      width: 150px;
      height: 150px;
      line-height: 150px;
      margin: 5px;
      background-color: #ffd200;
      font-size: 100px;
      color: white;
      text-align: center;
    }
    .box-item div{
      font-size: 14px;
      position: relative;
      top: -100px;
    }
    .box-26 {
      height: 400px;
    }
    .box-26 .box-item {
      align-self: flex-start;
    }
    .box-26 .end {
      align-self: flex-end;
    }
  </style>
</head>
<body>
  <div class="box box-26">
    <div class="box-item">1</div>
    <div class="box-item">2</div>
    <div class="box-item end">3<div>flex-end</div></div>
    <div class="box-item">4</div>
  </div>
</body>
</html>

image