long-list.uvue

<template>
  <scroll-view class="page" :scroll-top="pageScrollTop">
    <view class="search-bar" ref="header">
      <input placeholder="搜索..." />
    </view>
    <view class="swiper-list">
      <scroll-view ref="tabScroll" class="swiper-tabs" :scroll-x="true" :show-scrollbar="false">
        <!-- TODO 多一层 view -->
        <view>
          <view class="flex-row">
            <text ref="swipertab" class="swiper-tabs-item" :class="swiperIndex==index ? 'swiper-tabs-item-active' : ''"
              v-for="(item, index) in swiperList" :key="index" @click="onTabClick(index)">
              {{item.name}}
            </text>
          </view>
          <view ref="indicator" class="swiper-tabs-indicator"></view>
        </view>
      </scroll-view>
      <swiper ref="swiper" class="swiper-view" :current="swiperIndex" @transition="onSwiperTransition"
        @animationfinish="onSwiperAnimationfinish">
        <swiper-item class="swiper-item" v-for="(item, index) in swiperList" :key="index">
          <long-page ref="longPage" :type="item.type" :preload="item.preload"></long-page>
        </swiper-item>
      </swiper>
    </view>
  </scroll-view>
</template>

<script>
  import longPage from './long-list-page.uvue';

  type SwiperTabsItem = {
    x : number,
    w : number
  }

  type SwiperViewItem = {
    type : string,
    name : string,
    preload : Boolean,
  }

  /**
   * 根据权重在两个值之间执行线性插值.
   * @constructor
   * @param {number} value1 - 第一个值，该值应为下限.
   * @param {number} value2 - 第二个值，该值应为上限.
   * @param {number} amount - 应介于 0 和 1 之间，指示内插的权重.
   * @returns {number} 内插值
   */
  function lerpNumber(value1 : number, value2 : number, amount : number) : number {
    return (value1 + (value2 - value1) * amount)
  }

  export default {
    components: {
      longPage
    },
    data() {
      return {
        pageScrollTop: 0,
        swiperList: [
          {
            type: 'UpdatedDate',
            name: '最新上架',
            preload: true
          } as SwiperViewItem,
          {
            type: 'FreeHot',
            name: '免费热榜'
          } as SwiperViewItem,
          {
            type: 'PaymentHot',
            name: '付费热榜'
          } as SwiperViewItem,
          {
            type: 'HotList',
            name: '热门总榜'
          } as SwiperViewItem
        ] as SwiperViewItem[],
        swiperIndex: -1,
        $tabScrollView: null as null | INode,
        $indicatorNode: null as null | INode,
        $headerHeight: 0,
        $animationFinishIndex: 0,
        $swiperWidth: 0,
        $swiperTabsRect: [] as SwiperTabsItem[]
      }
    },
    onReady() {
      this.$tabScrollView = this.$refs.get('tabScroll') as INode
      this.$indicatorNode = this.$refs.get('indicator') as INode
      this.$headerHeight = (this.$refs["header"] as INode).offsetHeight
      this.$swiperWidth = (this.$refs["swiper"] as INode).getBoundingClientRect().width
      this.queryTabItemsSize()
      this.setSwiperIndex(0, true)
    },
    methods: {
      onTabClick(index : number) {
        this.setSwiperIndex(index, false)
      },
      onSwiperTransition(e : SwiperTransitionEvent) {
        // 微信 skyline 每项完成触发 Animationfinish，偏移值重置
        // 微信 webview 全部完成触发 Animationfinish，偏移值累加
        // 在滑动到下一个项的过程中，再次反向滑动，偏移值递减
        // uni-app-x 微信 webview 行为一致

        const offset_x = e.detail.dx

        // 重置差异，计算当前索引
        const current_offset_x = offset_x % this.$swiperWidth
        const current_offset_i = offset_x / this.$swiperWidth
        const current_index = this.$animationFinishIndex + current_offset_i.toInt()

        // 更新索引及边界检查
        let move_to_index = current_index
        if (current_offset_x > 0 && move_to_index < this.swiperList.length - 1) {
          move_to_index += 1
        } else if (current_offset_x < 0 && move_to_index > 0) {
          move_to_index -= 1
        }

        // 计算偏移百分比
        const percentage = Math.abs(current_offset_x) / this.$swiperWidth

        // 通知更新指示线
        this.updateTabIndicator(current_index, move_to_index, percentage)

        // 首次可见时初始化数据
        this.initSwiperItemPage(move_to_index)
      },
      onSwiperAnimationfinish(e : SwiperAnimationFinishEvent) {
        this.setSwiperIndex(e.detail.current, true)
        this.$animationFinishIndex = e.detail.current
      },
      queryTabItemsSize() {
        this.$swiperTabsRect.length = 0
        const tabs = this.$refs["swipertab"] as INode[]
        tabs.forEach((node) => {
          this.$swiperTabsRect.push({
            x: node.offsetLeft,
            w: node.offsetWidth
          } as SwiperTabsItem)
        })
      },
      setSwiperIndex(index : Number, updateIndicator : Boolean) {
        if (this.swiperIndex === index) {
          return
        }

        this.swiperIndex = index

        this.initSwiperItemPage(index)

        if (updateIndicator) {
          this.updateTabIndicator(index, index, 1)
        }
      },
      updateTabIndicator(current_index : number, move_to_index : number, percentage : number) {
        // 计算指示线
        const current_size = this.$swiperTabsRect[current_index]
        const move_to_size = this.$swiperTabsRect[move_to_index]
        const indicator_line_x = lerpNumber(current_size.x, move_to_size.x, percentage)
        const indicator_line_w = lerpNumber(current_size.w, move_to_size.w, percentage)

        // 更新指示线
        const x = indicator_line_x + indicator_line_w / 2
        this.$indicatorNode?.style?.setProperty('transform', `translateX(${x}px) scaleX(${indicator_line_w})`)

        // 滚动到水平中心位置
        const scroll_x = x - this.$swiperWidth / 2
        this.$tabScrollView?.setAttribute('scrollLeft', scroll_x)
      },
      initSwiperItemPage(index : Number) {
        if (!this.swiperList[index].preload) {
          this.swiperList[index].preload = true;
          (this.$refs["longPage"]! as ComponentPublicInstance[])[index].$callMethod('loadData')
        }
      }
    }
  }
</script>

<style>
  .flex-row {
    flex-direction: row;
  }

  .page {
    flex: 1;
  }

  .search-bar {
    padding: 10px;
  }

  .swiper-list {
    flex: 1;
    /* height: 100%; */
  }

  .swiper-tabs {
    background-color: #ffffff;
  }

  .swiper-tabs-item {
    color: #555;
    font-size: 16px;
    padding: 12px 25px;
  }

  .swiper-tabs-item-active {
    color: #007AFF;
  }

  .swiper-tabs-indicator {
    width: 1px;
    height: 2px;
    background-color: #007AFF;
  }

  .swiper-view {
    flex: 1;
  }

  .swiper-item {
    flex: 1;
  }
</style>