描述

模擬vant的Tab標(biāo)簽頁(yè)的標(biāo)簽滾動(dòng)效果
效果：選中元素播揪，在滾動(dòng)條的可視區(qū)域里面自動(dòng)居中瞒爬，頭尾兩端不用居中
vant效果：https://youzan.github.io/vant/#/zh-CN/tab

vant效果.jpg

代碼

<template>
  <div>
    <div class="scroll-box" ref="scrollBox">
      <div
        ref="scrollItem"
        class="item"
        :class="{ active: currentIndex == index }"
        v-for="(item, index) in 10"
        :key="index"
      >
        {{ index }}
      </div>
    </div>

    <div class="tips">點(diǎn)擊加減號(hào)改變索引再點(diǎn)擊啟動(dòng)按鈕排作，觀察滾動(dòng)！＝俊创橄！</div>

    <div>當(dāng)前索引是：{{ currentIndex }}</div>
    <div class="input-box">
      <div class="action">
        <div class="item" @click="reduce">-</div>
        <div class="item num">{{ currentIndex }}</div>
        <div class="item" @click="add">+</div>
      </div>
      <div class="start" @click="start">啟動(dòng)</div>
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      currentIndex: 0
    }
  },
  methods: {
    add() {
      this.currentIndex++
    },
    reduce() {
      this.currentIndex--
    },
    start() {
      /**
       * 1)先讓選中的元素滾到可視區(qū)域的最左邊 scrollLeft
       * 2)接著向右移動(dòng)容器一半的距離 containWidth / 2
       * 3)最后向左移動(dòng)item一半的距離 offsetWidth / 2
       */
      let lastSpot = this.$refs.scrollBox.scrollLeft
      const nextSpace = 7 //每次移動(dòng)距離
      let scrollItemTimer = setInterval(() => {
        this.$nextTick(() => {
          let offsetWidth = this.$refs.scrollItem[this.currentIndex].offsetWidth //item
          let scrollLeft = this.$refs.scrollItem[this.currentIndex].offsetLeft //選中的元素滾到可視區(qū)域的最左邊
          const containWidth = this.$refs.scrollBox.offsetWidth //容器的寬度
          let resultSpot = scrollLeft + offsetWidth / 2 - containWidth / 2 //最終要停留的點(diǎn)
          if (Math.abs(lastSpot - resultSpot) < nextSpace) {
            clearInterval(scrollItemTimer)
          }
          if (resultSpot >= lastSpot) {
            lastSpot = lastSpot + nextSpace
          } else {
            lastSpot = lastSpot - nextSpace
          }
          this.$refs.scrollBox.scrollTo(lastSpot, 0)
        })
      }, 15)
    }
  }
}
</script>

<style lang="less" scoped>
.scroll-box {
  margin-top: 50px;
  width: 330px;
  height: 40px;
  background-color: #ddd;
  white-space: nowrap;
  overflow-y: hidden;
  overflow-x: scroll;

  .item {
    display: inline-block;
    height: 100%;
    width: 90px;
    border-radius: 5px;
    background-color: #ff0;
    margin-right: 10px;
    text-align: center;
    line-height: 40px;
  }
  .item:nth-last-of-type(1) {
    margin-right: 0;
  }
}
.active {
  background-color: #0ff !important;
}
.tips {
  margin-top: 30px;
  font-weight: 700;
  color: #1989fa;
}
.input-box {
  width: 100%;
  display: flex;
  align-items: center;
  .action {
    display: flex;
    align-items: center;
    .item {
      width: 40px;
      height: 40px;
      background-color: #07c160;
      color: #fff;
      text-align: center;
      line-height: 40px;
      border-radius: 10px;
      margin-right: 5px;
    }
    .item.num {
      background-color: #ff976a;
    }
  }
  .start {
    width: 80px;
    height: 40px;
    background-color: #1989fa;
    color: #fff;
    margin-left: 100px;
    text-align: center;
    line-height: 40px;
    border-radius: 10px;
  }
}
</style>

圖片效果

居中滾動(dòng).gif

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