uniapp完成一个商品左右菜单互连的组件（代码加注解原理）

思路：
1.首先让两块区域各自滑动起来
2.当点击左边的item，右边对应的item就要滑到顶部。这时候就要获取到右边每个item到顶部的距离。然后再减掉不需要的元素位置。让scroll-top=该item距离顶部的位置
3.让左边菜单栏，每次点击的item都显示在中间。那么就要通过计算左边每个item的高度和整个左边菜单栏的高度并进行计算
4.在右边滚动时要进行监听，滚动到某个位置之后左边也要对应上所以就要调用对应的方法

<template>
	<view class="u-warp">
		<!-- 搜索 -->
		<view class="u-search-box">
			<view class="u-search-inner">
				<u-icon class="search-icon" name="search" color="#ccc" size="35"></u-icon>
				<u-input type="text" placeholder="请输入搜索关键字" />
			</view>
		</view>
		<!-- 内容 -->
		<view class="u-content-box">

			<!-- z左边 -->
			<scroll-view
			 scroll-with-animation
			  scroll-y="true" //开启滑动
			  :scroll-top="LeftScrollTop"   //动态设置滑动的位置在那
			  :scroll-into-view="itemId"    //没作用，可用于测试
				class="left-scroll menu-scroll-view">
				<view @tap.stop='switchTab(index)' class="u-tab-item" :class="[current == index? 'tab-action' :'']"
					v-for="(item,index) in data" :key='index'>
					<text>{{item}}</text>
				</view>
			</scroll-view>

			<!-- z右边 -->
			<scroll-view 
			scroll-y="true" 
			:scroll-top="RightScrollTop"
			 scroll-with-animation 
			 @scroll='rightScroll'
			 class="right-scroll">
				<view class="page-view">
					<view class="goods-item" :id="'item'+index" v-for="(item,index) in data" :key='index'>
						<view class="goods-title">
							<u-divider class="u-divider" color="#000" fontSize='35'
								style="background-color: transparent;">{{item}}</u-divider>
						</view>
						<!-- 类目 -->
						<view class="goods-category">
							<view class="category" v-for="(item,index) in category" :key='index'>
								{{item}}
							</view>
						</view>
						<!-- 商品 -->
						<view class="goods-details-box" v-for="(item,index) in 5" :key='index'>
							<view class="goods-text-box">
								<!-- <image src="" ></image> -->
								<view class="img">
									<image src="../../static/1.jpg" mode=""></image>
								</view>
								<view class="goods-text">
									<text class="goods-text-text">收音机收音机收音机收音机收音机收音机</text>
									<view class="num">
										商品编号：<text>12345648</text>
									</view>
								</view>
							</view>
							<view class="price-box">
								<view class="price">
									结算价：￥420
								</view>
								<u-button size="mini" type="warning" shape="square">月落</u-button>
							</view>
						</view>
					</view>
				</view>
			</scroll-view>
		</view>
	</view>
</template>

<script>
	export default {
		data() {
			return {
				data: ['热门推荐', '热门', '冷门', '主球', '篮球', '家电', '手机', '美剧'
				, '菜单', '日常', '骑车', '房产', '日历', '地产', '火锅',
				],
				category: ['全部', '常用品', '常用品', '常用品'],
				current: 0,
				RightScrollTop: '', //右边的scroll位置
				LeftScrollTop: 0, //左边的菜单的初始滚动位置
				LeftItemHight: 0, //左边菜单item的高度   Lefthight
				LeftHight: 0, //左边菜单的高度 
				
				oldRightScrollTop: 0, //右边滑动时记录的旧位置
				itemId: '', // 栏目右边scroll-view用于滚动的id
				RightTopArr: [], //右边菜单每个item距离top的高度
				RightHight: 0, //右边菜单的高度 
				time: null, //定时器
			};
		},
		onReady() {
			this.getRightItemTop();
		},
		methods: {
			// 点击左边的item
			async switchTab(index) {
				if (this.RightTopArr.length == 0) {
					await this.getRightItemTop();
				}
				if (index == this.current) return;
				this.LeftScrollTop = this.oldRightScrollTop;

				// 试图更新没有那么快，所以要用异步的$nextTick
				this.$nextTick(function() {
					this.RightScrollTop = this.RightTopArr[index];
					this.current = index;
					this.leftMenuStatus(index);
				})
			},
			// 获取一个目标元素的高度，相当于jq中的height
			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();
				})
			},
			// 设置左边菜单的滚动状态，让item居中显示
			async leftMenuStatus(index) {
				this.current = index;
				// 如果为0，意味着尚未初始化
				if (this.LeftHight == 0 || this.LeftItemHight == 0) {
					await this.getElRect('menu-scroll-view', 'LeftHight');
					await this.getElRect('u-tab-item', 'LeftItemHight');
				}
				// 将菜单活动item垂直居中
				// 先计算真个left一共多高，然后除以2就行了
				this.LeftScrollTop = index * this.LeftItemHight + this.LeftItemHight / 2 - this.LeftHight / 2;
			},


			// 获取右边菜单的每个item距离顶部的位置用一个数组来接收
			getRightItemTop() {
				// 异步操作
				new Promise(resolve => {
					let selectorQuery = uni.createSelectorQuery();
					// 获取节点的位置信息
					selectorQuery.selectAll('.goods-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.getRightItemTop();
							}, 10);
							return;
						}
						// 生成之后开始添加进去数组
						rects.forEach((rect) => {
							// 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.RightTopArr.push(rect.top - rects[0].top);
							resolve();
						})
					}).exec()
				})
			},

			// 获取右边的状态
			async rightScroll(e) {
				this.oldRightScrollTop = e.detail.scrollTop;
				if (this.RightTopArr.length == 0) {
					await this.getRightItemTop();
				}
				if (this.timer) return;
				if (!this.LeftHight) {
					await this.getElRect('menu-scroll-view', 'LeftHight');
				}
				setTimeout(() => { // 节流
					this.timer = null;
					// scrollHeight为右边菜单垂直中点位置
					let scrollHeight = e.detail.scrollTop + this.LeftHight / 2;
					for (let i = 0; i < this.RightTopArr.length; i++) {
						let height1 = this.RightTopArr[i];
						let height2 = this.RightTopArr[i + 1];
						// 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
						if (!height2 || scrollHeight >= height1 && scrollHeight < height2) {
							this.leftMenuStatus(i);
							return;
						}
					}
				}, 10)
			},
			// 相交
			async observer() {
				this.data.map((val, index) => {
					let observer = uni.createIntersectionObserver(this);
					// 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
					observer.relativeTo('.right-scroll', {
						top: 0
					}).observe('#item' + index, res => {
						if (res.intersectionRatio > 0) {
							let id = res.id.substring(4);
							this.leftMenuStatus(id);
						}
					})
				})
			},
		}
	}
</script>

<style lang="scss">
	.u-warp {
		height: calc(100vh);
		/* #ifdef H5 */
		height: calc(100vh - var(--window-top));
		/* #endif */
		display: flex;
		flex-direction: column;
		background-color: #F6F6F6;


		.u-search-box {
			margin-top: 10rpx;

			.u-search-inner {
				border-radius: 30rpx;
				display: flex;
				justify-content: center;
				flex-direction: row;
				align-items: center;
				width: 80%;
				margin: 0 auto;
				border: 1px solid #007AFF;
				height: 60rpx;
				padding: 3rpx;

				.search-icon {
					margin: 0 10rpx;
				}
			}
		}

		.u-content-box {
			margin-top: 40rpx;
			display: flex;
			flex: 1;
			overflow: hidden;  //1

			.left-scroll {
				background-color: #EEEEEE;
				width: 200rpx;
				// text-align: center;
				font-size: 35rpx;
				display: inline-block;
				height: 100%;

				.u-tab-item {
					display: flex;
					align-items: center;
					justify-content: center;
					height: 100rpx;
					font-size: 26rpx;

					text {}
				}

				.tab-action {
					color: #E50A0B;
					background-color: #F6F6F6;
					font-weight: 600;

					&::before {
						content: '';
						display: block;
						background-color: #E50A0B;
						width: 10rpx;
						height: 50rpx;
						position: absolute;
						left: 0;
					}

				}
			}

			.right-scroll {
				margin-left: 20rpx;
				display: inline-block;

				// background-color: #F29100;
				.page-view {
					.goods-item {
						.goods-title {
							.u-divider {
								font-weight: 600;
							}
						}

						.goods-category {

							display: flex;
							flex-direction: row;
							align-items: center;
							text-align: center;
							justify-content: space-around;
							white-space: nowrap;
							overflow-x: scroll;
							overflow-y: hidden;
							flex-wrap: wrap;

							.category {
								background-color: #FFFFFF;
								width: 100rpx;
								height: 50rpx;
								border-radius: 10rpx;
								display: flex;
								justify-content: center;
								align-items: center;
								// flex-wrap: wrap;
							}
						}

						.goods-details-box {
							background-color: white;
							margin-top: 20rpx;
							margin-right: 20rpx;
							padding: 10rpx;
							border-radius: 20rpx;

							.goods-text-box {
								display: flex;
								flex-direction: row;

								.img {
									width: 150rpx;
									height: 150rpx;
									background-color: #C0C0C0;

									image {
										width: 110%;
										height: 100%;
									}
								}

								.goods-text {
									margin-left: 10rpx;

									.goods-text-text {
										font-weight: 600;
										font-size: 30rpx;
									}

									.num {
										font-weight: 600;
										margin-top: 20rpx;

										text {
											color: #ccc;
										}
									}
								}
							}

							.price-box {
								display: flex;
								flex-direction: row;
								margin-top: 40rpx;

								.price {
									font-size: 36rpx;
									color: #F95659;
								}
							}
						}
					}
				}
			}
		}
	}
</style>

遇到的问题需要自己去检查元素，逻辑哪里错了。
1.scroll-view无法滚动，检查一下元素父元素是否设置了宽高，子元素是否排成竖排或者横排，是否设置了overflow
2.设置了伸缩盒子之后要注意一下设置宽高防止变形