转载自：
作者：阿远Carry
链接：https://juejin.cn/post/6916146797328990216
来源：稀土掘金
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
有些小伙伴看到标题就在想
我做这动态图片肯定不那么麻烦，我随便找几个图贴上去啊！
我只能说：小了，格局小了！
像有些业务场景：比如大屏项目，如果使用png.gif这类，总会失真！
但SVG不会，SVG永远的神！
所以，这篇文章教大家如何快速实现SVG动态图标！
类似这样～
1.寻找图标素材（SVG标签）
我推荐大家去 iconfont 网站，随便找个图标
把鼠标放在图标上，点击下载按钮
会出现如下页面，点击复制SVG代码
你就会得到如下代码
<svg t="1610274780071" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="35827" width="200" height="200">
<path d="M722.944 501.76h173.568c13.312 0 24.576-10.752 24.576-24.576 0-13.312-10.752-24.576-24.576-24.576h-173.568c-27.136 0-53.76 9.216-75.264 25.088L296.96 734.72c-3.072 2.048-6.144 3.584-9.728 4.096-8.704 1.024-17.408 1.536-26.112 1.536-39.424-1.536-75.776-18.432-102.912-48.128-27.136-30.208-40.448-69.12-37.376-109.056 5.12-69.632 55.808-123.392 121.344-132.608 1.536 29.184 7.68 57.344 18.944 84.48 4.096 9.216 12.8 15.36 22.528 15.36 3.072 0 6.144-0.512 9.216-2.048 12.288-5.12 18.432-19.456 13.312-31.744-10.24-25.088-15.36-51.712-15.36-78.848C290.816 323.584 384 230.4 498.176 230.4c92.672 0 174.592 61.952 199.68 151.04 3.584 12.8 17.408 20.48 30.208 16.896 12.8-3.584 20.48-17.408 16.896-30.208-30.72-110.08-132.096-186.88-246.784-186.88-129.024 0-236.032 95.744-253.44 219.648-93.184 8.192-165.888 82.432-173.056 178.688-3.584 52.736 14.336 105.984 50.176 145.408 35.84 39.936 84.48 62.464 137.728 64.512H266.24c9.728 0 18.944-0.512 28.672-2.048 11.776-1.536 23.04-6.656 32.256-13.312l350.72-257.024c12.288-9.728 28.672-15.36 45.056-15.36zM897.024 740.352h-301.568c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h301.568c13.312 0 24.576-10.752 24.576-24.576 0-13.824-11.264-24.576-24.576-24.576z" fill="#1875F0" p-id="35828"></path>
<path d="M643.072 598.016c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h141.312c13.312 0 24.576-10.752 24.576-24.576 0-13.312-10.752-24.576-24.576-24.576h-141.312zM928.256 598.016h-62.464c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h62.464c13.312 0 24.576-10.752 24.576-24.576 0-13.312-11.264-24.576-24.576-24.576zM510.464 740.352H448c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h62.464c13.312 0 24.576-10.752 24.576-24.576 0-13.824-11.264-24.576-24.576-24.576z" fill="#1875F0" p-id="35829"></path>
</svg>
有的小伙伴就觉得这是啥玩意啊？我看不懂啊！
小伙伴们，先别慌，hold住！
其实这段代码很简单！
就是 svg 标签嵌套了两个 path 标签罢了
svg 标签中 viewBox="0 0 1024 1024" 属性代表是 1024 × 1024 视图
path 标签中的 d 属性定义路径
简单准确理解：就是在 1024 × 1024 的虚拟画布上作画
而 width="200" height="200" 是控制实际svg的大小
也就是等比例缩放，把 1024 × 1024 图片缩放到 200 × 200，还不会失真，真好！
最后一个 path 标签中的 fill="#1875F0" 是填充色
2. 编写动画样式 （CSS）
再编写样式之前，我们还需要对之前svg的内容进行处理
在每个 path 标签中
删除 fill="#1875F0" 原本的填充颜色属性
添加 fill="#fff" 与背景相同的填充颜色
增加 class="icon-path" class类名
增加 stroke="#1875F0" 描绘路径颜色属性
增加 stroke-width="3" 描绘路径的宽度
如下：
<svg t="1610274780071" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="35827" width="200" height="200">
<path class="icon-path" stroke="#1875F0" stroke-width="3" d="M722.944 501.76h173.568c13.312 0 24.576-10.752 24.576-24.576 0-13.312-10.752-24.576-24.576-24.576h-173.568c-27.136 0-53.76 9.216-75.264 25.088L296.96 734.72c-3.072 2.048-6.144 3.584-9.728 4.096-8.704 1.024-17.408 1.536-26.112 1.536-39.424-1.536-75.776-18.432-102.912-48.128-27.136-30.208-40.448-69.12-37.376-109.056 5.12-69.632 55.808-123.392 121.344-132.608 1.536 29.184 7.68 57.344 18.944 84.48 4.096 9.216 12.8 15.36 22.528 15.36 3.072 0 6.144-0.512 9.216-2.048 12.288-5.12 18.432-19.456 13.312-31.744-10.24-25.088-15.36-51.712-15.36-78.848C290.816 323.584 384 230.4 498.176 230.4c92.672 0 174.592 61.952 199.68 151.04 3.584 12.8 17.408 20.48 30.208 16.896 12.8-3.584 20.48-17.408 16.896-30.208-30.72-110.08-132.096-186.88-246.784-186.88-129.024 0-236.032 95.744-253.44 219.648-93.184 8.192-165.888 82.432-173.056 178.688-3.584 52.736 14.336 105.984 50.176 145.408 35.84 39.936 84.48 62.464 137.728 64.512H266.24c9.728 0 18.944-0.512 28.672-2.048 11.776-1.536 23.04-6.656 32.256-13.312l350.72-257.024c12.288-9.728 28.672-15.36 45.056-15.36zM897.024 740.352h-301.568c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h301.568c13.312 0 24.576-10.752 24.576-24.576 0-13.824-11.264-24.576-24.576-24.576z" fill="#fff" p-id="35828"></path>
<path class="icon-path" stroke="#1875F0" stroke-width="3" d="M643.072 598.016c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h141.312c13.312 0 24.576-10.752 24.576-24.576 0-13.312-10.752-24.576-24.576-24.576h-141.312zM928.256 598.016h-62.464c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h62.464c13.312 0 24.576-10.752 24.576-24.576 0-13.312-11.264-24.576-24.576-24.576zM510.464 740.352H448c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h62.464c13.312 0 24.576-10.752 24.576-24.576 0-13.824-11.264-24.576-24.576-24.576z" fill="#fff" p-id="35829"></path>
</svg>
增加css代码：
.icon-path {
animation: icon-path-animation 8s ease-in infinite;
}
@keyframes icon-path-animation {
0% {
stroke-dasharray: 4917;
stroke-dashoffset: 4917;
}
40% {
stroke-dasharray: 4917;
stroke-dashoffset: 0;
fill: #fff;
}
60% {
stroke-dasharray: 4917;
stroke-dashoffset: 0;
fill: #1875F0;
}
100% {
stroke-dasharray: 4917;
stroke-dashoffset: 0;
fill: #1875F0;
}
}
大功告成！
哈哈哈，别急
这里有些细节你应该明白！
首先我们用了animation 动画属性：
指定了 icon-path-animation 关键帧的名称
持续时间为 8s
ease-in 由慢到快的 动画过程
infinite 无限次数循环
而，在关键帧中：
小伙伴们比较陌生的应该是 stroke-dasharray 和 stroke-dashoffset 两个属性
stroke-dasharray 表示 路径之间的空白间隙长度
比如将上述 css 替换成这段代码
.icon-path {
stroke-dasharray: 1000;
}
肉眼可见的他有 1000 的间隙值
还有，细心的小伙伴会发现 有个array的字眼
确实他可以传“数组”进去
例如
.icon-path {
stroke-dasharray: 60, 50, 60;
}
他就会出现
接着就是 stroke-dashoffset 空白间隙的偏移量
.icon-path {
stroke-dasharray: 1000;
stroke-dashoffset: 200;
}
其实你可以发现，就是空白间隙就被偏移 200
所以，stroke-dashoffset: 4917; 到 stroke-dashoffset: 0;
应该是 从无到有的过程
这个图标 最长的 path 约为 4917
毕竟，stroke-dashoffset 空白间隙偏移为4917，那就是 4917 - 4917 = 0，此时的 path 应该 0
而当 stroke-dashoffset 空白间隙偏移为 0, 4917 - 0 = 4917，也就是这个图标足够显示的路径长度
或许，有的小伙伴最莫名其妙的是：你怎么知道这个图标路径长度是 4917 啊？胡说八道吗？
其实不是我算的，我用了以下的JS代码获得的
const iconPath = document.getElementsByClassName('icon-path') // 获取 path 标签
for (let i = 0; i < iconPath.length; i++) {
const item = iconPath[i]
console.log(item.getTotalLength()) // 获得 path 路径长度
}
可以发现，最长度是 4916.69335937， 约为 4917
所以，我们只要选取最长path作为最大间隙就足够！
CSS代码连贯流程应该是：
从 0 到 40% 绘制全部描边路径
从 40% 到 60% 填充颜色
从 60% 100% 保持不变
整个过程从慢到快，持续 8s， 无限循环
所以，看完以上你应该可以快速开发一个动态SVG图标了吧
附上全部代码(html文件)
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>SVG动态图标</title>
<style>
.icon-path {
animation: icon-path-animation 8s ease-in infinite;
}
@keyframes icon-path-animation {
0% {
stroke-dasharray: 4917;
stroke-dashoffset: 4917;
fill: #fff;
}
40% {
stroke-dasharray: 4917;
stroke-dashoffset: 0;
fill: #fff;
}
60% {
stroke-dasharray: 4917;
stroke-dashoffset: 0;
fill: #1875F0;
}
100% {
stroke-dasharray: 4917;
stroke-dashoffset: 0;
fill: #1875F0;
}
}
</style>
</head>
<body>
<svg t="1610274780071" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="35827" width="200" height="200">
<path class="icon-path" stroke="#1875F0"stroke-width="3" d="M722.944 501.76h173.568c13.312 0 24.576-10.752 24.576-24.576 0-13.312-10.752-24.576-24.576-24.576h-173.568c-27.136 0-53.76 9.216-75.264 25.088L296.96 734.72c-3.072 2.048-6.144 3.584-9.728 4.096-8.704 1.024-17.408 1.536-26.112 1.536-39.424-1.536-75.776-18.432-102.912-48.128-27.136-30.208-40.448-69.12-37.376-109.056 5.12-69.632 55.808-123.392 121.344-132.608 1.536 29.184 7.68 57.344 18.944 84.48 4.096 9.216 12.8 15.36 22.528 15.36 3.072 0 6.144-0.512 9.216-2.048 12.288-5.12 18.432-19.456 13.312-31.744-10.24-25.088-15.36-51.712-15.36-78.848C290.816 323.584 384 230.4 498.176 230.4c92.672 0 174.592 61.952 199.68 151.04 3.584 12.8 17.408 20.48 30.208 16.896 12.8-3.584 20.48-17.408 16.896-30.208-30.72-110.08-132.096-186.88-246.784-186.88-129.024 0-236.032 95.744-253.44 219.648-93.184 8.192-165.888 82.432-173.056 178.688-3.584 52.736 14.336 105.984 50.176 145.408 35.84 39.936 84.48 62.464 137.728 64.512H266.24c9.728 0 18.944-0.512 28.672-2.048 11.776-1.536 23.04-6.656 32.256-13.312l350.72-257.024c12.288-9.728 28.672-15.36 45.056-15.36zM897.024 740.352h-301.568c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h301.568c13.312 0 24.576-10.752 24.576-24.576 0-13.824-11.264-24.576-24.576-24.576z" fill="#fff" p-id="35828"></path>
<path class="icon-path" stroke="#1875F0" stroke-width="3" d="M643.072 598.016c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h141.312c13.312 0 24.576-10.752 24.576-24.576 0-13.312-10.752-24.576-24.576-24.576h-141.312zM928.256 598.016h-62.464c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h62.464c13.312 0 24.576-10.752 24.576-24.576 0-13.312-11.264-24.576-24.576-24.576zM510.464 740.352H448c-13.312 0-24.576 10.752-24.576 24.576 0 13.312 10.752 24.576 24.576 24.576h62.464c13.312 0 24.576-10.752 24.576-24.576 0-13.824-11.264-24.576-24.576-24.576z" fill="#fff" p-id="35829"></path>
</svg>
<script>
const iconPath = document.getElementsByClassName('icon-path') // 获取 path 标签
for (let i = 0; i < iconPath.length; i++) {
const item = iconPath[i]
console.log(item.getTotalLength()) // 获得 path 路径长度
}
</script>
</body>
</html>
最后：
本篇只是实现了简单动画效果
如果想要复杂效果，无非是写好几个不同 animation
如果小伙伴们认真看完明白其中原理，就可以完实现出来的