uniapp完成一个商品左右菜单互连的组件（代码加注解原理）

女爷i 2022-09-08 11:55 92阅读 0赞

> 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">
    		
    		<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>
    		
    		<view class="u-content-box">
    
    			
    			<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>
    
    			
    			<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>
    						
    						<view class="goods-category">
    							<view class="category" v-for="(item,index) in category" :key='index'>
    								{ { item}}
    							</view>
    						</view>
    						
    						<view class="goods-details-box" v-for="(item,index) in 5" :key='index'>
    							<view class="goods-text-box">
    								
    								<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<ItemHight
    				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