使用css绘制箭头

使用css也能直接写出箭头符号，这样不用都使用图片能减少打包的大小。下面是一些常用箭头的css写法：

// 向上的箭头
    <view class="button-up"></view>
// css的内容
  .button-up {
    position: relative;
    padding: 5px;
    margin: 10px auto;
    background: #000;
    height: 50px;
    width: 50px;
    border-radius: 50%;
  }

  .button-up::after {
    content: "";
    position: absolute;
    left: 17px;
    z-index: 11;
    display: block;
    width: 25px;
    height: 25px;
    border-top: 2px solid #fff;
    border-left: 2px solid #fff;
    top: 20px;
    transform: rotate(45deg);
  }

// 想下的箭头
    <view class="button-down"></view>
  .button-down {
    position: relative;
    padding: 5px;
    margin: 10px auto;
    background: #000;
    height: 50px;
    width: 50px;
    border-radius: 50%;
  }

  .button-down::after {
    content: "";
    position: absolute;
    left: 17px;
    z-index: 11;
    display: block;
    width: 25px;
    height: 25px;
    border-top: 2px solid #fff;
    border-left: 2px solid #fff;
    top: 10px;
    transform: rotate(225deg);
  }

向右的箭头

    <view class="arrow-right"></view>
    <view class="arrow-left"></view>
    <view class="long-arrow-right"></view>
    <view class="long-arrow-left"></view>

  .arrow-right,
  .arrow-left,
  .long-arrow-right,
  .long-arrow-left{
    display: block;
    margin: 30px auto;
    width: 25px;
    height: 25px;
    border-top: 2px solid #000;
    border-left: 2px solid #000;
  }
  .arrow-right,
  .long-arrow-right{
    transform: rotate(135deg);
  }

  .arrow-left,
  .long-arrow-left{
    transform: rotate(-45deg);
  }
  .long-arrow-right::after,
  .long-arrow-left::after{
    content: "";
    display: block;
    width: 2px;
    height: 45px;
    background-color: black;
    transform: rotate(-45deg) translate(15px, 4px);
    left: 0;
    top: 0;
  }

三角行箭头

    <view class="triangle-bottom"></view>
    <view class="triangle-top"></view>
    <view class="triangle-right"></view>
    <view class="triangle-left"></view>
  .triangle-left,
  .triangle-right,
  .triangle-top,
  .triangle-bottom{
    width: 0;
    height: 0;
    margin: 10px auto;
  }
  .triangle-left,
  .triangle-right{
    border-top:
      18px solid transparent;
    border-bottom:
      18px solid transparent;


  }
  .triangle-top,
  .triangle-bottom{
    border-left:
      18px solid transparent;
    border-right:
      18px solid transparent;
  }

  .triangle-right{
    border-left:
      30px solid black;
  }
  .triangle-left{
    border-right:
      30px solid black;
  }
  .triangle-top{
    border-bottom:
      30px solid black;
  }
  .triangle-bottom{
    border-top:
      30px solid black;
  }