摘要：主要用到的知識(shí)點(diǎn)參閱菜鳥(niǎo)教程動(dòng)畫(huà)延時(shí)實(shí)現(xiàn)說(shuō)明用于區(qū)別四個(gè)不同點(diǎn)，里放通用樣式重點(diǎn)如果了解，看這個(gè)更清晰些，如果不懂，看下面生成的定死容器的高度，不然會(huì)上下浮動(dòng)橫向排列子元素縱向排列子元素去掉最后一個(gè)

參閱菜鳥(niǎo)教程： http://www.runoob.com/css3/cs...

frame

animation / 動(dòng)畫(huà)延時(shí)

flex

說(shuō)明： loading-1/2/3/4 用于區(qū)別四個(gè)不同點(diǎn)，loading-item 里放通用樣式

如果了解 less，看這個(gè)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，不然會(huì)上下浮動(dòng)
  margin: 20px 0;
  display: flex;
  align-items: center; // 橫向排列子元素
  justify-content: center; // 縱向排列子元素
  .loading-item{
    height: @load-box-height;
    width: 10px;
    margin-right: 10px;
    &:last-child{ // 去掉最后一個(gè)的右邊距
      margin-right: 0;
    }
  }
  &-1{
  // 【參數(shù)分別為】 動(dòng)畫(huà)key名，一次動(dòng)畫(huà)的持續(xù)時(shí)間，循環(huán)方式，過(guò)濾規(guī)則，動(dòng)畫(huà)起始延時(shí)時(shí)間
    -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; 
    // 通過(guò)控制延時(shí)，只用一個(gè)keyframe 就能做出漸變效果
    -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;}
  // 設(shè)置動(dòng)畫(huà)中間的高度，此時(shí)為最低，為原高度的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;}
}