uniapp监听滚动实现顶部透明度变化

 效果如图：

实现思路：

1、使用onPageScroll监听页面滚动，改变导航条的透明度；

2、关于顶部图片的高度：

如果是小程序：使用getMenuButtonBoundingClientRect获取胶囊顶部距离和胶囊高度；

如果是H5：给个自定义高度就行；

3、透明度opacity的计算公式：1 - (this.imgHeight - e.scrollTop) / this.imgHeight；

4、相关组件绑定行内样式，完活！

完整代码：

<template>
	<view class="">

		<!-- 顶部导航 -->
		<fa-navbar :title="vuex_table_title || '宝乐名车服务'" ref="navbar"
			:style="[{opacity:opacity},{position:'fixed'},{'zIndex':'999'}]"></fa-navbar>
		<!-- 顶部图片 -->
		<view class="head_img" :style="[{overflow: 'hidden'},{height:imgHeight+'px'}]">
			<img :style="{width: '100%'}"
				src="https://sa.ffep.online:20093/uploads/20240907/590a5bb30e86dbbbe6a9172a41ba157a.png" alt="" />
		</view>
		<!-- 搜索 -->
		<view class="u-p-20 u-bg-white u-flex u-col-center" v-if="is_show">
			<view class="u-flex-1">
				<fa-search :mode="2"></fa-search>
			</view>
			<view class="u-p-l-15 u-p-r-5 u-flex u-col-center" v-if="is_order">
				<fa-orderby-select :filterList="filterList" :orderList="orderList" :multiple="true"
					@change="goOrderBy"></fa-orderby-select>
			</view>
		</view>
		<!-- 分类 -->
		<view class="u-border-top" v-if="isTab">
			<u-tabs :list="tabList" :active-color="theme.bgColor" :bar-width="tabwidth" name="title" :is-scroll="true"
				:current="current" @change="change"></u-tabs>
		</view>
		<!-- 轮播图 -->
		<view class="" v-if="is_show">
			<u-swiper :title="true" border-radius="0" height="320" :list="bannerList" @click="openPage"></u-swiper>
		</view>
		<!-- 列表 -->
		<fa-article-item :archives-list="archivesList"></fa-article-item>
		<!-- 为空 -->
		<view class="u-m-t-60 u-p-t-60" v-if="is_empty">
			<u-empty text="暂无内容展示" mode="list"></u-empty>
		</view>
		<!-- 加载更多 -->
		<view class="u-p-30" v-if="archivesList.length">
			<u-loadmore bg-color="#f4f6f8" :status="status" />
		</view>
		<!-- 回到顶部 -->
		<u-back-top :scroll-top="scrollTop" :icon-style="{ color: theme.bgColor }"
			:custom-style="{ backgroundColor: lightColor }"></u-back-top>
		<!-- 底部导航 -->
		<fa-tabbar></fa-tabbar>
	</view>
</template>

<script>
	import {
		archives
	} from '@/common/fa.mixin.js';
	export default {
		mixins: [archives],
		computed: {
			bannerList() {
				return this.vuex_config.bannerList || [];
			}
		},
		watch: {

		},
		onPageScroll(e) {
			let calc = 1 - (this.imgHeight - e.scrollTop) / this.imgHeight;
			this.opacity = calc
		},
		data() {
			return {
				imgHeight: 0,
				opacity: 0
			};
		},
		onLoad(e) {
			// #ifdef MP-WEIXIN || APP-PLUS
			// 获取状态栏和胶囊位置
			const {
				top,
				height
			} = uni.getMenuButtonBoundingClientRect()
			this.imgHeight = (top + height+10)*1.5;
			// #endif

			// #ifdef H5
			this.imgHeight = 100;
			// #endif
			
			let query = e;
			if (JSON.stringify(query) == '{}') {
				query = e;
			}
			if (query && JSON.stringify(query) != '{}') {
				this.params = query;
			} else {
				this.params = {
					channel: -1,
					model: -1
				}
			}
			this.getCategory();
			this.getArchives();
		},
		methods: {

		},
	};
</script>

<style lang="scss">
	.head_img {
		// position: fixed;
		top: 0;
		left: 0;
		width: 100%;
		transition: opacity 0.2s ease;
		/* 平滑过渡 */
	}

	page {
		background-color: #f4f6f8;
	}
</style>