chelvc-custom/src/pages/client/clientPackage/category.vue

<template>
  <view class="u-wrap">
    <view class="u-menu-wrap">
      <scroll-view scroll-y scroll-with-animation class="u-tab-view menu-scroll-view" :scroll-top="scrollTop"
        :scroll-into-view="itemId">
        <view v-for="(item, index) in left_first_list" :key="index" class="u-tab-item"
          :class="[current == index ? 'u-tab-item-active' : '']" @tap.stop="handleLeftMenuClick(index)">
          <text class="u-line-1">{{ item.name }}</text>
        </view>
      </scroll-view>

      <scroll-view :scroll-top="scrollRightTop" scroll-y scroll-with-animation class="right-box" @scroll="rightScroll">
        <view class="page-view">
          <view class="class-item" :id="'item' + index" v-for="(item, index) in left_first_list" :key="index">
            <view class="item-title">
              <text>{{ item.name }}</text>
            </view>
            <view class="item-container">
              <view class="thumb-box" v-for="(child, childIndex) in item.children" :key="childIndex"
                @click="handleItemClick(child.id, child.name)">
                <image v-if="child.icon != ''" class="item-menu-image" :src="child.icon" mode=""></image>
                <view v-else class="item-menu-image row-c" style="background-color: #f4f6f8">
                  <text style="font-size: 20rpx; color: #d0d0d0">加载失败</text>
                </view>
                <view class="item-menu-name">{{ child.name }}</view>
              </view>
            </view>
          </view>
        </view>
      </scroll-view>
    </view>
  </view>
</template>

<script>
  // import {
  //   buildTree
  // } from '@/utils/tools.js';
  import {
    maintainCategories
  } from '@/api/client/business.js';
  export default {
    data() {
      return {
        scrollTop: 0, //tab标题的滚动条位置
        oldScrollTop: 0, // tab标题的滚动条旧位置
        current: 0, // 预设当前项的值
        menuHeight: 0, // 左边菜单的高度
        menuItemHeight: 0, // 左边菜单item的高度
        itemId: '', // 栏目右边scroll-view用于滚动的id
        cateList: [], // 渲染的数据
        arr: [], // 储存距离顶部高度的数组
        scrollRightTop: 0, // 右边栏目scroll-view的滚动条高度
        timer: null, // 定时器
        left_first_list: [], //左侧一级列表
      };
    },
    onLoad() {
      // this.cateList = buildTree(this.getCache('categories'));
    },
    onReady() {
      this.getMenuItemTop();
    },
    mounted() {
      // 获取左侧一级列表信息
      maintainCategories().then(res => {
        console.log('@@@@res',res);
        this.left_first_list = res.data;
      });
    },
    methods: {
      /**
       * 获取一个目标元素的高度
       * @elClass 元素的类名
       * @dataVal 储存高度的对象
       */
      getElRect(elClass, dataVal) {
        new Promise((resolve, reject) => {
          const query = uni.createSelectorQuery().in(this);
          query
            .select('.' + elClass)
            .fields({
                size: true,
              },
              res => {
                // 如果节点尚未生成，res值为null，循环调用执行
                if (!res) {
                  setTimeout(() => {
                    this.getElRect(elClass);
                  }, 10);
                  return;
                }
                this[dataVal] = res.height;
                resolve();
              },
            )
            .exec();
        });
      },
      /**
       * 获取右边菜单每个item到顶部的距离
       * 储存到 arr 数组里面用于后面滚动判断
       */
      getMenuItemTop() {
        new Promise(resolve => {
          let selectorQuery = uni.createSelectorQuery();
          selectorQuery
            .selectAll('.class-item')
            .boundingClientRect(rects => {
              // 如果节点尚未生成，rects值为[](因为用selectAll，所以返回的是数组)，循环调用执行
              if (!rects.length) {
                setTimeout(() => {
                  this.getMenuItemTop();
                }, 10);
                return;
              }
              rects.forEach(rect => {
                // 视情况而定，这里减去rects[0].top，是因为第一项顶部可能不是贴到导航栏(比如有个搜索框的情况)
                // this.arr.push(rect.top - rects[0].top);
                this.arr.push(rect.top);
                resolve();
              });
            })
            .exec();
        });
      },
      /**
       * 观测元素相交状态
       * 检测右边scroll-view的id为itemxx的元素与right-box的相交状态
       * 如果跟.right-box底部相交，就动态设置左边栏目的活动状态
       */
      async observer() {
        this.cateList.map((val, index) => {
          let observer = uni.createIntersectionObserver(this);
          observer
            .relativeTo('.right-box', {
              top: 0,
            })
            .observe('#item' + index, res => {
              if (res.intersectionRatio > 0) {
                let id = res.id.substring(4);
                this.leftMenuStatus(id);
              }
            });
        });
      },
      /**
       * 设置左边菜单的滚动状态
       * @index 传入的 ID
       */
      async leftMenuStatus(index) {
        this.current = index;
        // 如果为0，意味着尚未初始化
        if (this.menuHeight == 0 || this.menuItemHeight == 0) {
          await this.getElRect('menu-scroll-view', 'menuHeight');
          await this.getElRect('u-tab-item', 'menuItemHeight');
        }
        // 将菜单活动item垂直居中
        this.scrollTop = index * this.menuItemHeight + this.menuItemHeight / 2 - this.menuHeight / 2;
      },
      /**
       * 点击左边的栏目切换
       * @index 传入的 ID
       */
      async handleLeftMenuClick(index) {
        if (this.arr.length == 0) {
          await this.getMenuItemTop();
        }
        if (index == this.current) return;
        this.scrollRightTop = this.oldScrollTop;
        this.$nextTick(function() {
          this.scrollRightTop = this.arr[index];
          this.current = index;
          this.leftMenuStatus(index);
        });
      },
      /**
       * 右边菜单滚动
       * 如果不存在height2，意味着数据循环已经到了最后一个，设置左边菜单为最后一项即可
       */
      async rightScroll(e) {
        this.oldScrollTop = e.detail.scrollTop;
        if (this.arr.length == 0) {
          await this.getMenuItemTop();
        }
        if (this.timer) return;
        if (!this.menuHeight) {
          await this.getElRect('menu-scroll-view', 'menuHeight');
        }
        setTimeout(() => {
          // 节流
          this.timer = null;
          // scrollHeight为右边菜单垂直中点位置
          // let scrollHeight = e.detail.scrollTop + this.menuHeight / 2;
          // scrollHeight为右边菜单头部位置
          let scrollHeight = e.detail.scrollTop + 20;
          for (let i = 0; i < this.arr.length; i++) {
            let height1 = this.arr[i];
            let height2 = this.arr[i + 1];
            if (!height2 || (scrollHeight >= height1 && scrollHeight < height2)) {
              this.leftMenuStatus(i);
              return;
            }
          }
        }, 10);
      },
      handleItemClick(id, name) {
        this.$Router.push(`/pages/client/clientPackage/storeList?id=${id}`);
      },
    },
  };
</script>

<style scoped>
  .u-wrap {
    /* #ifdef H5 */
    height: calc(100vh - var(--window-top));
    /* #endif */
    display: flex;
    flex-direction: column;
    height: 100vh;
  }

  .u-search-box {
    padding: 18rpx 30rpx;
  }

  .u-menu-wrap {
    flex: 1;
    display: flex;
    overflow: hidden;
  }

  .u-tab-view {
    width: 200rpx;
    height: 100%;
  }

  .u-tab-item {
    height: 110rpx;
    background: #f6f6f6;
    box-sizing: border-box;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 26rpx;
    color: #444;
    font-weight: 400;
    line-height: 1;
  }

  .u-tab-item-active {
    position: relative;
    color: #06a446;
    font-size: 30rpx;
    font-weight: 500;
    background: #d6ffe7;
  }

  .u-tab-item-active::before {
    content: '';
    position: absolute;
    border-left: 4px solid #06a446;
    height: 52rpx;
    left: 0;
    top: 29rpx;
  }

  .u-tab-view {
    height: 100%;
  }

  .right-box {
    background-color: rgb(250, 250, 250);
  }

  .page-view {
    padding: 16rpx;
  }

  .class-item {
    margin-bottom: 30rpx;
    background-color: #fff;
    padding: 16rpx;
    border-radius: 8rpx;
  }

  .class-item:last-child {
    min-height: 100vh;
  }

  .item-title {
    font-size: 26rpx;
    color: #06a446;
    font-weight: bold;
  }

  .item-menu-name {
    margin-top: 8rpx;
    font-weight: normal;
    font-size: 24rpx;
    color: #06a446;
  }

  .item-container {
    display: flex;
    flex-wrap: wrap;
  }

  .thumb-box {
    width: 33.333333%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    margin-top: 20rpx;
  }

  .item-menu-image {
    width: 120rpx;
    height: 120rpx;
  }
</style>