组成
弹性盒子没有设置高，就会自动拉伸
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<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex布局-组成</title><style>/* 弹性容器 */.box {display: flex;height: 300px;border: 1px solid #000;}/* 弹性盒子：沿着主轴方向排列 */.box div {width: 200px;/* height: 100px; */background-color: pink;}</style>
</head><body><div class="box"><div>1</div><div>2</div><div>3</div><div>1</div><div>2</div><div>3</div><div>1</div><div>2</div><div>3</div></div></body></html>
主轴对齐方式
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<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex布局-主轴对齐方式</title><style>.box {display: flex;/* justify-content: flex-start; *//* justify-content: flex-end; *//* 居中 *//* justify-content: center; *//* 父级剩余的尺寸分配成间距 *//* 弹性盒子之间的间距相等 *//* justify-content: space-between; *//* 间距出现在弹性盒子两侧 *//* 视觉效果：弹性盒子之间的间距是两端间距的2倍 *//* justify-content: space-around; *//* 各个间距都相等 */justify-content: space-evenly;height: 300px;border: 1px solid #000;}.box div {width: 200px;height: 100px;background-color: pink;}</style>
</head><body><div class="box"><div>1</div><div>2</div><div>3</div></div></body></html>
侧轴对齐方式
如果没有设置侧轴对齐方式和弹性盒子的高度，默认是stretch。
这也是为什么上面有提到，高度没设置会自动拉伸的原因
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<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex布局-侧轴对齐方式</title><style>.box {display: flex;/* 弹性盒子在侧轴方向没有尺寸才能拉伸 *//* align-items: stretch; *//* align-items: center; *//* align-items: flex-start; */align-items: flex-end;height: 300px;border: 1px solid #000;}/* 第二个div，侧轴居中对齐 */.box div:nth-child(2) {align-self: center;}.box div {width: 200px;height: 100px;background-color: pink;}</style>
</head>
<body><div class="box"><div>1</div><div>2</div><div>3</div></div></body></html>
修改主轴方向
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<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex布局-修改主轴方向</title><style>.box {display: flex;/* 修改主轴方向 垂直方向；侧轴自动变换到水平方向 */flex-direction: column;/* 主轴在垂直，视觉效果：垂直居中 */justify-content: center;/* 侧轴在水平，视觉效果：水平居中 */align-items: center;width: 150px;height: 120px;background-color: pink;}img {width: 32px;height: 32px;}</style>
</head><body><div class="box"><img src="./images/1.png" alt=""><span>媒体</span></div></body></html>弹性伸缩比
注意！使用弹性伸缩比，控制的是主轴方向！
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<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex布局-弹性伸缩比</title><style>/* 默认情况下，主轴方向尺寸是靠内容撑开；侧轴默认拉伸 */.box {display: flex;flex-direction: column;height: 300px;border: 1px solid #000;}.box div {/* height: 100px; */background-color: pink;}.box div:nth-child(1) {width: 200px;}.box div:nth-child(2) {flex: 1;}.box div:nth-child(3) {flex: 2;}</style>
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<body><div class="box"><div>1</div><div>2</div><div>3</div></div></body></html>可以看到盒子3的高度是盒子2的两倍
为什么？
因为总份数 = 1+2，盒子2占了一份，盒子3占了两份
弹性盒子换行
想自动换行，在父级加wrap即可
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex布局-弹性换行</title><style>.box {display: flex;flex-wrap: wrap;/* 不换行 *//* flex-wrap: nowrap; */justify-content: space-between;height: 300px;border: 1px solid #000;}.box div {width: 200px;height: 100px;background-color: pink;}</style>
</head><body><div class="box"><div>1</div><div>2</div><div>3</div><div>4</div><div>5</div><div>6</div><div>7</div><div>8</div><div>9</div><div>10</div><div>11</div><div>12</div></div></body></html>
行对齐方式
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<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex布局-行对齐方式</title><style>.box {display: flex;flex-wrap: wrap;justify-content: space-between;/* 调整 行对齐方式：对单行弹性盒子不生效 *//* align-content: flex-start; *//* align-content: flex-end; *//* align-content: center; *//* align-content: space-between; *//* align-content: space-around; *//* 没有代码提示 */align-content: space-evenly;height: 400px;border: 1px solid #000;}.box div {width: 200px;height: 100px;background-color: pink;}</style>
</head>
<body><div class="box"><div>1</div><div>2</div><div>3</div><div>4</div><div>5</div><div>6</div><div>7</div><div>8</div></div></body></html>
综合案例
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<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title><style>* {margin: 0;padding: 0;box-sizing: border-box;/* 盒子自动内减 */}li {list-style: none;}.box {border: 1px solid black;width: 1200px;height: 418px;border-radius: 10px;/* 直角变圆角 */margin: 50px auto;/* 和上面产生距离50px，水平居中 */}.box ul {display: flex;flex-wrap: wrap;justify-content: space-between;align-content: space-between;padding: 90px 40px 90px 60px;/* 左上右下 */height: 418px;}.box li {width: 500px;height: 88px;/* background-color: pink; */display: flex;flex-wrap: wrap;}.box .pic {margin-right: 15px;}.box .text h4 {/* 文字行高等于上边距+下边距+文字高 */line-height: 40px;font-size: 20px;font-weight: 400;/* 文字粗细 */color: #333;}.box .text p {font-size: 14px;color: #666;}</style>
</head><body><div class="box"><ul><li><div class="pic"><img src="./p1.png" alt=""></div><div class="text"><h4>一键发布多端</h4><p>发布视频到抖音短视频、西瓜视频及今日头条</p></div></li><li><div class="pic"><img src="./p2.png" alt=""></div><div class="text"><h4>管理视频内容</h4><p>支持修改已发布稿件状态和实时查询视频审核状态</p></div></li><li><div class="pic"><img src="./p3.png" alt=""></div><div class="text"><h4>发布携带组件</h4><p>支持分享内容携带小程序、地理位置信息等组件</p></div></li><li><div class="pic"><img src="./p4.png" alt=""></div><div class="text"><h4>数据评估分析</h4><p>获取视频在对应产品内的数据表现、获取抖音热点</p></div></li></ul></div>
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