摘要：主要用到的知識點參閱菜鳥教程動畫延時實現說明用于區別四個不同點，里放通用樣式重點如果了解，看這個更清晰些，如果不懂，看下面生成的定死容器的高度，不然會上下浮動橫向排列子元素縱向排列子元素去掉最后一個

參閱菜鳥教程： http://www.runoob.com/css3/cs...

frame

animation / 動畫延時

flex

說明： loading-1/2/3/4 用于區別四個不同點，loading-item 里放通用樣式

如果了解 less，看這個更清晰些，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，不然會上下浮動
  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{ // 去掉最后一個的右邊距
      margin-right: 0;
    }
  }
  &-1{
  // 【參數分別為】 動畫key名，一次動畫的持續時間，循環方式，過濾規則，動畫起始延時時間
    -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; 
    // 通過控制延時，只用一個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;}
  // 設置動畫中間的高度，此時為最低，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;}
}