纯CSS3实现圆弧(圆圈)百分比动画进度条

原文链接： http://caibaojian.com/css3-radial-progress-bar.html

• clip
• transform
• keyframes
• animation-duration
• animation-delay
• animation-name
• animation-iteration-count
• animation-fill-mode
• animation-timing-function

代码如下：

首先定义基本样式：

.wrapper {
  width: 100px; /* Set the size of the progress bar */
  height: 100px;
  position: absolute; /* Enable clipping */
  clip: rect(0px, 100px, 100px, 50px); /* Hide half of the progress bar */
}
/* Set the sizes of the elements that make up the progress bar */
.circle {
  width: 80px;
  height: 80px;
  border: 10px solid green;
  border-radius: 50px;
  position: absolute;
  clip: rect(0px, 50px, 100px, 0px);
}

接着是动画规则·

/* Using the data attributes for the animation selectors. */
/* Base settings for all animated elements */
div[data-anim~=base] {
  -webkit-animation-iteration-count: 1;  /* Only run once */
  -webkit-animation-fill-mode: forwards; /* Hold the last keyframe */
  -webkit-animation-timing-function:linear; /* Linear animation */
}

.wrapper[data-anim~=wrapper] {
  -webkit-animation-duration: 0.01s; /* Complete keyframes asap */
  -webkit-animation-delay: 3s; /* Wait half of the animation */
  -webkit-animation-name: close-wrapper; /* Keyframes name */
}

.circle[data-anim~=left] {
  -webkit-animation-duration: 6s; /* Full animation time */
  -webkit-animation-name: left-spin;
}

.circle[data-anim~=right] {
  -webkit-animation-duration: 3s; /* Half animation time */
  -webkit-animation-name: right-spin;
}

最后是动画帧

//code from http://caibaojian.com/css3-radial-progress-bar.html
/* Rotate the right side of the progress bar from 0 to 180 degrees */
@-webkit-keyframes right-spin {
  from {
    -webkit-transform: rotate(0deg);
  }
  to {
    -webkit-transform: rotate(180deg);
  }
}
/* Rotate the left side of the progress bar from 0 to 360 degrees */
@-webkit-keyframes left-spin {
  from {
    -webkit-transform: rotate(0deg);
  }
  to {
    -webkit-transform: rotate(360deg);
  }
}
/* Set the wrapper clip to auto, effectively removing the clip */
@-webkit-keyframes close-wrapper {
  to {
    clip: rect(auto, auto, auto, auto);
  }
}

操作原理：

首先：是定义三个动画，第一个是最外层，让他只显示一半，然后运行3s，同时右边运行3s,从0到180度。

接着：到了180度之后，释放外层的显示一半，让他自动显示其他。然后右边的停止动画并停在那里。

最后：左边的在原来的基础（跟右边一样运行3s，同样转过180度）再继续转动180度。

来源： 前端开发博客