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Flex 布局教程：实例篇

资源编号:76088 前端相关问题前端热度：110

原文地址：http://www.ruanyifeng.com/blog/2015/07/flex-examples.html

上一篇文章介绍了Flex布局的语法，今天介绍常见布局的Flex写法。

你会看到，不管是什么布局，Flex往往都可以几行命令搞定。

![bs64](https://img.handsomemark.com/2019/11/13/cfdad18c-05fb-11ea-b909-0242ac140002.png)

# 一、骰子的布局
骰子的一面，最多可以放置9个点。

![bs64](https://img.handsomemark.com/2019/11/13/17378f02-05fc-11ea-8f74-0242ac140002.png)

下面，就来看看Flex如何实现，从1个点到9个点的布局。你可以到[codepen](http://codepen.io/LandonSchropp/pen/KpzzGo "codepen")查看Demo。

![bs64](https://img.handsomemark.com/2019/11/13/2192ff04-05fc-11ea-8ba4-0242ac140002.png)

如果不加说明，本节的HTML模板一律如下。

```
<div class="box">
  <span class="item"></span>
</div>
```
上面代码中，div元素（代表骰子的一个面）是Flex容器，span元素（代表一个点）是Flex项目。如果有多个项目，就要添加多个span元素，以此类推。

### 1.1 单项目
首先，只有左上角1个点的情况。Flex布局默认就是首行左对齐，所以一行代码就够了。

![bs64](https://img.handsomemark.com/2019/11/13/464c80e0-05fc-11ea-a8ab-0242ac140002.png)

```
.box {
  display: flex;
}
```
设置项目的对齐方式，就能实现居中对齐和右对齐。

![bs64](https://img.handsomemark.com/2019/11/13/4c61f528-05fc-11ea-8966-0242ac140002.png)

```
.box {
  display: flex;
  justify-content: center;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/582988a8-05fc-11ea-8ad5-0242ac140002.png)
```
.box {
  display: flex;
  justify-content: flex-end;
}
```
设置交叉轴对齐方式，可以垂直移动主轴。

![bs64](https://img.handsomemark.com/2019/11/13/6543841c-05fc-11ea-9d3b-0242ac140002.png)

```
.box {
  display: flex;
  align-items: center;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/73e7a11a-05fc-11ea-b590-0242ac140002.png)
```
.box {
  display: flex;
  justify-content: center;
  align-items: center;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/94cf48d8-05fc-11ea-b110-0242ac140002.png)
```
.box {
  display: flex;
  justify-content: center;
  align-items: flex-end;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/9daf084e-05fc-11ea-8663-0242ac140002.png)
```
.box {
  display: flex;
  justify-content: flex-end;
  align-items: flex-end;
}
```
### 1.2 双项目

![bs64](https://img.handsomemark.com/2019/11/13/a849bfa6-05fc-11ea-aa39-0242ac140002.png)
```
.box {
  display: flex;
  justify-content: space-between;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/d0cb598a-05fc-11ea-851e-0242ac140002.png)
```
.box {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/dbfd0c90-05fc-11ea-a3cc-0242ac140002.png)
```
.box {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  align-items: center;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/e549a8c6-05fc-11ea-9505-0242ac140002.png)
```
.box {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  align-items: flex-end;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/f20b01ae-05fc-11ea-9ffa-0242ac140002.png)
```
.box {
  display: flex;
}

.item:nth-child(2) {
  align-self: center;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/f96e4e6a-05fc-11ea-83d8-0242ac140002.png)
```
.box {
  display: flex;
  justify-content: space-between;
}

.item:nth-child(2) {
  align-self: flex-end;
}
```

### 1.3 三项目

![bs64](https://img.handsomemark.com/2019/11/13/0064f840-05fd-11ea-8070-0242ac140002.png)

```
.box {
  display: flex;
}

.item:nth-child(2) {
  align-self: center;
}

.item:nth-child(3) {
  align-self: flex-end;
}
```
### 1.4 四项目

![bs64](https://img.handsomemark.com/2019/11/13/0b230f6a-05fd-11ea-9edc-0242ac140002.png)
```
.box {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  align-content: space-between;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/1ae67900-05fd-11ea-8d75-0242ac140002.png)

HTML代码如下。

```
<div class="box">
  <div class="column">
    <span class="item"></span>
    <span class="item"></span>
  </div>
  <div class="column">
    <span class="item"></span>
    <span class="item"></span>
  </div>
</div>
```
CSS代码如下。

```
.box {
  display: flex;
  flex-wrap: wrap;
  align-content: space-between;
}

.column {
  flex-basis: 100%;
  display: flex;
  justify-content: space-between;
}
```

### 1.5 六项目

![bs64](https://img.handsomemark.com/2019/11/13/2c4d76f8-05fd-11ea-a7f6-0242ac140002.png)
```
.box {
  display: flex;
  flex-wrap: wrap;
  align-content: space-between;
}
```

![bs64](https://img.handsomemark.com/2019/11/13/345f93c6-05fd-11ea-a76f-0242ac140002.png)
```
.box {
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
  align-content: space-between;
}
```

HTML代码如下。

```
<div class="box">
  <div class="row">
    <span class="item"></span>
    <span class="item"></span>
    <span class="item"></span>
  </div>
  <div class="row">
    <span class="item"></span>
  </div>
  <div class="row">
     <span class="item"></span>
     <span class="item"></span>
  </div>
</div>
```
CSS代码如下。

```
.box {
  display: flex;
  flex-wrap: wrap;
}

.row{
  flex-basis: 100%;
  display:flex;
}

.row:nth-child(2){
  justify-content: center;
}

.row:nth-child(3){
  justify-content: space-between;
}
```

### 1.6 九项目

![bs64](https://img.handsomemark.com/2019/11/13/4571ed94-05fd-11ea-8173-0242ac140002.png)
```
.box {
  display: flex;
  flex-wrap: wrap;
}
```

# 二、网格布局

### 2.1 基本网格布局
最简单的网格布局，就是平均分布。在容器里面平均分配空间，跟上面的骰子布局很像，但是需要设置项目的自动缩放。

![bs64](https://img.handsomemark.com/2019/11/13/53302ce8-05fd-11ea-8759-0242ac140002.png)

HTML代码如下。

```
<div class="Grid">
  <div class="Grid-cell">...</div>
  <div class="Grid-cell">...</div>
  <div class="Grid-cell">...</div>
</div>
```
CSS代码如下。
```

.Grid {
  display: flex;
}

.Grid-cell {
  flex: 1;
}
```

### 2.2 百分比布局
某个网格的宽度为固定的百分比，其余网格平均分配剩余的空间。

![bs64](https://img.handsomemark.com/2019/11/13/3eae34fe-0602-11ea-ba23-0242ac140002.png)

HTML代码如下。

```

<div class="Grid">
  <div class="Grid-cell u-1of4">...</div>
  <div class="Grid-cell">...</div>
  <div class="Grid-cell u-1of3">...</div>
</div>
```

```
.Grid {
  display: flex;
}

.Grid-cell {
  flex: 1;
}

.Grid-cell.u-full {
  flex: 0 0 100%;
}

.Grid-cell.u-1of2 {
  flex: 0 0 50%;
}

.Grid-cell.u-1of3 {
  flex: 0 0 33.3333%;
}

.Grid-cell.u-1of4 {
  flex: 0 0 25%;
}
```

# 三、圣杯布局
圣杯布局（Holy Grail Layout）指的是一种最常见的网站布局。页面从上到下，分成三个部分：头部（header），躯干（body），尾部（footer）。其中躯干又水平分成三栏，从左到右为：导航、主栏、副栏。

![bs64](https://img.handsomemark.com/2019/11/13/530f9a1e-0602-11ea-a17d-0242ac140002.png)

HTML代码如下。

```
<body class="HolyGrail">
  <header>...</header>
  <div class="HolyGrail-body">
    <main class="HolyGrail-content">...</main>
    <nav class="HolyGrail-nav">...</nav>
    <aside class="HolyGrail-ads">...</aside>
  </div>
  <footer>...</footer>
</body>
```

CSS代码如下。

```
.HolyGrail {
  display: flex;
  min-height: 100vh;
  flex-direction: column;
}

header,
footer {
  flex: 1;
}

.HolyGrail-body {
  display: flex;
  flex: 1;
}

.HolyGrail-content {
  flex: 1;
}

.HolyGrail-nav, .HolyGrail-ads {
  /* 两个边栏的宽度设为12em */
  flex: 0 0 12em;
}

.HolyGrail-nav {
  /* 导航放到最左边 */
  order: -1;
}
```
如果是小屏幕，躯干的三栏自动变为垂直叠加。

```
@media (max-width: 768px) {
  .HolyGrail-body {
    flex-direction: column;
    flex: 1;
  }
  .HolyGrail-nav,
  .HolyGrail-ads,
  .HolyGrail-content {
    flex: auto;
  }
}
```
# 四、输入框的布局
我们常常需要在输入框的前方添加提示，后方添加按钮。

![bs64](https://img.handsomemark.com/2019/11/13/639861e0-0602-11ea-8ffd-0242ac140002.png)

HTML代码如下。

```
<div class="InputAddOn">
  <span class="InputAddOn-item">...</span>
  <input class="InputAddOn-field">
  <button class="InputAddOn-item">...</button>
</div>
```

CSS代码如下。

```
.InputAddOn {
  display: flex;
}

.InputAddOn-field {
  flex: 1;
}
```

# 五、悬挂式布局
有时，主栏的左侧或右侧，需要添加一个图片栏。

![bs64](https://img.handsomemark.com/2019/11/13/7247f430-0602-11ea-aa45-0242ac140002.png)

HTML代码如下。

```
<div class="Media">
  <img class="Media-figure" src="" alt="">
  <p class="Media-body">...</p>
</div>
```
CSS代码如下。

```
.Media {
  display: flex;
  align-items: flex-start;
}

.Media-figure {
  margin-right: 1em;
}

.Media-body {
  flex: 1;
}
```

# 六、固定的底栏
有时，页面内容太少，无法占满一屏的高度，底栏就会抬高到页面的中间。这时可以采用Flex布局，让底栏总是出现在页面的底部。

![bs64](https://img.handsomemark.com/2019/11/13/838558d2-0602-11ea-944e-0242ac140002.png)

HTML代码如下。

```
<body class="Site">
  <header>...</header>
  <main class="Site-content">...</main>
  <footer>...</footer>
</body>
```
CSS代码如下。

```
.Site {
  display: flex;
  min-height: 100vh;
  flex-direction: column;
}

.Site-content {
  flex: 1;
}
```
# 七，流式布局
每行的项目数固定，会自动分行。

![bs64](https://img.handsomemark.com/2019/11/13/936fc08e-0602-11ea-819b-0242ac140002.png)

CSS的写法。

```
.parent {
  width: 200px;
  height: 150px;
  background-color: black;
  display: flex;
  flex-flow: row wrap;
  align-content: flex-start;
}

.child {
  box-sizing: border-box;
  background-color: white;
  flex: 0 0 25%;
  height: 50px;
  border: 1px solid red;
}
```