index.vue

<template>
  <view class="big">
    <view class="tabItem" v-for="(item,index) in list" :key="index" @click="changeValue(index)">
        <view :class="[actionIndex===index?'textAction':'textDefault']">
            {{item.name}}
        </view>
      <view :class="[actionIndex===index?'borderLineAction':(flag?'borderLineDefault':'borderLine')]"></view>
    </view>
  </view>
</template>

<script>
export default {
  props:{
    list:{
        type:Array,
        default(){
            return []
        }
    },
    newIndex:{
        type:Number,
        default(){
            return 0
        }
    }
  },
  watch:{
    newIndex(val){
        this.flag = true
        this.actionIndex = val
    }
  },
  data() {
    return {
        flag:false,
        actionIndex:0
    };
  },
  methods: {
    changeValue(index){
        this.flag = true
        this.actionIndex = index
        this.$emit('changeTab',index)
    }
  }
};
</script>

<style lang="scss" scoped>
.big {
  height: 68rpx;
  display: flex;
  align-items: center;
  padding-top: 3rpx;

  .tabItem {
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;

    .textAction{
        width: 100%;
        text-align: center;
        margin-bottom: 12rpx;
        font-size: 24rpx;
        font-family: PingFangSC-Medium, PingFang SC;
        font-weight: 500;
        color: #333333;
    }

    .textDefault{
        width: 100%;
        text-align: center;
        margin-bottom: 12rpx;
        font-size: 24rpx;
        font-family: PingFangSC-Regular, PingFang SC;
        font-weight: 400;
        color: #666666;
    }

    .borderLineAction {
      margin: 0 auto;
      height: 4rpx;
      background: #0050f6;
    }
    .borderLineAction {
      animation-name: showani;
      animation-duration: 0.5s;
      animation-fill-mode: forwards;
      @keyframes showani {
        0% {
            width: 0rpx;
        }
        100% {
            width: 64rpx;
        }
      }
    }

    .borderLine {
        height: 4rpx;
    }

    .borderLineDefault {
      margin: 0 auto;
      height: 4rpx;
      background: #0050f6;
    }
    .borderLineDefault {
      animation-name: hideani;
      animation-duration: 0.5s;
      animation-fill-mode: forwards;
      @keyframes hideani {
        0% {
            width: 64rpx;
        }
        100% {
            width: 0rpx;
        }
      }
    }
  }
}
</style>