前端每日实战:134# 视频演示如何用 CSS 和 GSAP 创作一个树枝发芽的 loader
效果预览
按下右侧的“点击预览”按钮可以在当前页面预览,点击链接可以全屏预览。
https://codepen.io/comehope/pen/LJmpXZ
可交互视频
此视频是可以交互的,你可以随时暂停视频,编辑视频中的代码。
请用 chrome, safari, edge 打开观看。
https://scrimba.com/p/pEgDAM/cdD8WHV
源代码下载
每日前端实战系列的全部源代码请从 github 下载:
https://github.com/comehope/front-end-daily-challenges
代码解读
定义 dom,容器包含 2 个元素,branch
代表枝,leaves
代表叶,叶有 6 个子元素,代表 6 个叶片:
<figure class="sapling">
<div class="branch"></div>
<div class="leaves">
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
</div>
</figure>
居中显示:
body {
margin: 0;
height: 100vh;
display: flex;
align-items: center;
justify-content: center;
background-color: black;
}
定义容器尺寸,并设置子元素水平居中:
.sapling {
position: relative;
width: 5em;
height: 17.5em;
font-size: 10px;
display: flex;
justify-content: center;
}
画出树枝:
.branch {
position: absolute;
width: 0.2em;
height: inherit;
border-radius: 25%;
background: burlywood;
}
定义树叶容器,设置为叶片在垂直方向均匀分布,并且从下到上排列:
.leaves {
position: absolute;
width: inherit;
height: 15em;
top: 1em;
display: flex;
flex-direction: column-reverse;
}
设置叶片的尺寸和和背景颜色:
.leaves span {
width: 2.5em;
height: 2.5em;
background-color: limegreen;
}
设置左右叶片的各自样式:
.leaves span:nth-child(odd) {
border-bottom-left-radius: 3em;
border-top-right-radius: 3em;
transform-origin: right bottom;
align-self: flex-start;
}
.leaves span:nth-child(even) {
border-bottom-right-radius: 3em;
border-top-left-radius: 3em;
transform-origin: left bottom;
align-self: flex-end;
}
至此,静态效果绘制完成,接下来开始写动画脚本。
引入 GSAP 库:
<script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/2.0.2/TweenMax.min.js"></script>
声明一个时间线对象:
let animation = new TimelineMax();
增加树枝的入场动画效果,并为这个动画设置一个标签 branch
:
animation.from('.branch', 4, {scaleY: 0, ease: Power1.easeOut}, 'branch');
增加树叶的入场动画效果,它的参数中有 3 个 0.5
,从左到右的含义分别是动画时长、多个叶片动画的间隔时长、相对 branch
标签动画的延迟时间:
animation.from('.branch', 4, {scaleY: 0, ease: Power1.easeOut}, 'branch')
.staggerFrom('.leaves span', 0.5, {scale: 0, ease: Power1.easeOut}, 0.5, 0.5, 'branch');
增加叶片变黄的动画效果:
animation.from('.branch', 4, {scaleY: 0, ease: Power1.easeOut}, 'branch')
.staggerFrom('.leaves span', 0.5, {scale: 0, ease: Power1.easeOut}, 0.5, 0.5, 'branch')
.to(['.branch', '.leaves span'], 3, {backgroundColor: 'yellow'});
增加淡出效果:
animation.from('.branch', 4, {scaleY: 0, ease: Power1.easeOut}, 'branch')
.staggerFrom('.leaves span', 0.5, {scale: 0, ease: Power1.easeOut}, 0.5, 0.5, 'branch')
.to(['.branch', '.leaves span'], 3, {backgroundColor: 'yellow'})
.to(['.branch', '.leaves span'], 1, {autoAlpha: 0});
修改声明时间线的代码,使动画重复播放:
let animation = new TimelineMax({repeat: -1, repeatDelay: 0.5});
大功告成!