用 CSS3 动画功能，做一个有逼格的加载动画

摘要：主要用到的知识点参阅菜鸟教程动画延时实现说明用于区别四个不同点，里放通用样式重点如果了解，看这个更清晰些，如果不懂，看下面生成的定死容器的高度，不然会上下浮动横向排列子元素纵向排列子元素去掉最后一个

参阅菜鸟教程： http://www.runoob.com/css3/cs...

frame

animation / 动画延时

flex

说明： loading-1/2/3/4 用于区别四个不同点，loading-item 里放通用样式

如果了解 less，看这个更清晰些，如果不懂，看下面生成的 css

LESS

@red: #FF3B30;
@orange: #FF9500;
@black: #373737;
@green: #4CD964;

@load-box-height: 50px;

.loading{
  height: @load-box-height; // 定死容器的高度，不然会上下浮动
  margin: 20px 0;
  display: flex;
  align-items: center; // 横向排列子元素
  justify-content: center; // 纵向排列子元素
  .loading-item{
    height: @load-box-height;
    width: 10px;
    margin-right: 10px;
    &:last-child{ // 去掉最后一个的右边距
      margin-right: 0;
    }
  }
  &-1{
  // 【参数分别为】 动画key名，一次动画的持续时间，循环方式，过滤规则，动画起始延时时间
    -webkit-animation: load-frame 1s infinite linear 0s;
    -o-animation: load-frame 1s infinite linear 0s;
    animation: load-frame 1s infinite linear 0s;
    background-color: @red;
  }
  &-2{
    -webkit-animation: load-frame 1s infinite linear 0.25s; 
    // 通过控制延时，只用一个keyframe 就能做出渐变效果
    -o-animation: load-frame 1s infinite linear 0.25s;
    animation: load-frame 1s infinite linear 0.25s;
    background-color: @orange;
  }
  &-3{
    -webkit-animation: load-frame 1s infinite linear 0.5s;
    -o-animation: load-frame 1s infinite linear 0.5s;
    animation: load-frame 1s infinite linear 0.5s;
    background-color: @black;
  }
  &-4{
    -webkit-animation: load-frame 1s infinite linear 0.75s;
    -o-animation: load-frame 1s infinite linear 0.75s;
    animation: load-frame 1s infinite linear 0.75s;
    background-color: @green;
  }
}

@keyframes load-frame {
  0% {height: @load-box-height;}
  50% {height: @load-box-height * 0.25;}
  // 设置动画中间的高度，此时为最低，为原高度的25%
  100% {height: @load-box-height;}
}

@-webkit-keyframes load-frame { // safari & chrome
  0% {height: @load-box-height;}
  50% {height: @load-box-height * 0.25;}
  100% {height: @load-box-height;}
}

CSS

.loading {
  height: 50px;
  margin: 20px 0;
  display: flex;
  align-items: center;
  justify-content: center;
}
.loading .loading-item {
  height: 50px;
  width: 10px;
  margin-right: 10px;
}
.loading .loading-item:last-child {
  margin-right: 0;
}
.loading-1 {
  -webkit-animation: load-frame 1s infinite linear 0s;
  -o-animation: load-frame 1s infinite linear 0s;
  animation: load-frame 1s infinite linear 0s;
  background-color: #FF3B30;
}
.loading-2 {
  -webkit-animation: load-frame 1s infinite linear 0.25s;
  -o-animation: load-frame 1s infinite linear 0.25s;
  animation: load-frame 1s infinite linear 0.25s;
  background-color: #FF9500;
}
.loading-3 {
  -webkit-animation: load-frame 1s infinite linear 0.5s;
  -o-animation: load-frame 1s infinite linear 0.5s;
  animation: load-frame 1s infinite linear 0.5s;
  background-color: #373737;
}
.loading-4 {
  -webkit-animation: load-frame 1s infinite linear 0.75s;
  -o-animation: load-frame 1s infinite linear 0.75s;
  animation: load-frame 1s infinite linear 0.75s;
  background-color: #4CD964;
}
@keyframes load-frame {
  0% {height: 50px;}
  50% {height: 12.5px;}
  100% {height: 50px;}
}
@-webkit-keyframes load-frame {
  0% {height: 50px;}
  50% {height: 12.5px;}
  100% {height: 50px;}
}