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1、背景
最近在做公司的一款小程序,其中有一块的设计的是在列表做上下滚动的是时候,顶部的tab栏跟着一起联动,当点击tab栏的时候,列表数据也跟随联动。
顶部的头部区域不跟随列表滚动;头部区域以下属于滚动区域。
2、实现
2.1 原理介绍
这个地方的实现主要借助了微信小程序原生的scroll-view组件。
使用它的 scroll-into-view 属性,可以实现点击顶部的tab栏,将页面滚动到指定的列表位置;
使用 bindscroll 事件,可以知道当前页面滚动的距离,根据滚动的距离做tab栏的切换操作;
2.1 页面布局代码
先说下界面的整体布局,主要分为两部分,头部固定区域 + 可滚动列表区域。
可滚动的列表区域的标题栏当滚动一定的距离后,它也要固定在顶部。
代码实现:
<!--index.wxml--><view class="list"><!--顶部固定区域--><view style="height: 88rpx;width: 100%;background-color: burlywood;text-align: center;">头部区域</view><!--可滚动区域--><scroll-view scroll-y="true" style="width: 100%; height: {{scrollAreaHeight}}px;" bindscroll="scroll" scroll-into-view="{{scrollToItem}}" scroll-with-animation="true" scroll-top="{{scrollTop}}"> <!--水平滚动的tab栏--> <scroll-view scroll-x="true" style="height: 88rpx;width: 100%;"> <view class="head-area {{float ? 'head-float' : ''}}" > <view class="head-area-item {{curSelectTab === index ? 'head-area-item-select' : ''}}" wx:for="{{appGroupList}}" bindtap="tabClick" data-index="{{index}}"> {{item.name}} </view> </view> </scroll-view><!--数据列表--><view class="list-group" style="height: {{listGroupHeight}}px;"> <view class="list-group-item" id="v_{{index}}" wx:for="{{appGroupList}}" data-index="{{index}}"> <view class="group-name"> {{item.name}} </view> <view class="group-children" > <view wx:for="{{item.children}}" class="group-children-item" style="width: {{itemWidth}}px;"> <image src="{{item.url}}"></image> <view>{{item.name}}</view> </view> </view> </view></view> </scroll-view></view>
在布局代码中有几个点需要注意:
scrollAreaHeight 滚动区域的高度计算。 --- 通过获取当前设备的窗口高度减去顶部固定区域的高度
水平tab栏是否置顶。 --- 根据页面的滚动距离来判断,如果滚动距离 大于或者等于 水平tab栏的高度,则置顶;
设置数据列表的id="v_{{index}}" id,后续点击tab栏滚动到指定的位置就是根据这个id去实现的。
2.2 样式代码
.list{ width: 100%; height: 100%; display: flex; flex-direction: column;}.head-area{ display: flex; flex-direction: row; flex-wrap: nowrap; height: 88rpx; width: 100%; padding: 0 10;}.head-area-item{ display: flex; height: 88rpx; text-align: center; width: 150rpx; align-items: center; justify-content: center;}.head-area-item-select{ color: #09bb07;}image{ width: 88rpx; height: 88rpx;}.list-group{ display: flex; width: 100%; height: 1000%; flex-direction: column;}.list-group-item{ display: flex; width: 100%; background-color: #aaa; flex-direction: column;}.group-name{ height: 88rpx; display: flex; text-align: center; align-items: center; margin-left: 20rpx;}.group-children{ display: flex; flex-direction: row; flex-wrap: wrap; width: 100%;}.group-children-item{ height: 160rpx; display: flex; flex-direction: column; justify-content: center; align-items: center;}.head-float{ position: fixed; top: 88rpx; background-color: #ffffff;}
2.3 逻辑代码
// index.jsPage({ heightArr: [], //记录scroll-view滚动过程中距离顶部的高度 distance: 0, data: { appGroupList:[ {name:"分组01",children:[{"name":"测试0","url":"/images/bluetooth.png"}, {"name":"测试1","url":"/images/bluetooth.png"}, {"name":"测试2","url":"/images/bluetooth.png"}, {"name":"测试3","url":"/images/bluetooth.png"}, {"name":"测试4","url":"/images/bluetooth.png"}, {"name":"测试5","url":"/images/bluetooth.png"}, {"name":"测试6","url":"/images/bluetooth.png"}, {"name":"测试7","url":"/images/bluetooth.png"}]}, {name:"分组02",children:[{"name":"测试0","url":"/images/bluetooth.png"}, {"name":"测试1","url":"/images/bluetooth.png"}, {"name":"测试2","url":"/images/bluetooth.png"}, {"name":"测试3","url":"/images/bluetooth.png"}, {"name":"测试4","url":"/images/bluetooth.png"}, {"name":"测试5","url":"/images/bluetooth.png"}, {"name":"测试6","url":"/images/bluetooth.png"}, {"name":"测试7","url":"/images/bluetooth.png"}]}, {name:"分组03",children:[{"name":"测试0","url":"/images/bluetooth.png"}, {"name":"测试1","url":"/images/bluetooth.png"}, {"name":"测试2","url":"/images/bluetooth.png"}, {"name":"测试3","url":"/images/bluetooth.png"}, {"name":"测试4","url":"/images/bluetooth.png"}, {"name":"测试5","url":"/images/bluetooth.png"}, {"name":"测试6","url":"/images/bluetooth.png"}, {"name":"测试7","url":"/images/bluetooth.png"}]}, {name:"分组04",children:[{"name":"测试0","url":"/images/bluetooth.png"}, {"name":"测试1","url":"/images/bluetooth.png"}, {"name":"测试2","url":"/images/bluetooth.png"}, {"name":"测试3","url":"/images/bluetooth.png"}, {"name":"测试4","url":"/images/bluetooth.png"}, {"name":"测试5","url":"/images/bluetooth.png"}, {"name":"测试6","url":"/images/bluetooth.png"}, {"name":"测试7","url":"/images/bluetooth.png"}]}, {name:"分组05",children:[{"name":"测试0","url":"/images/bluetooth.png"}, {"name":"测试1","url":"/images/bluetooth.png"}, {"name":"测试2","url":"/images/bluetooth.png"}, {"name":"测试3","url":"/images/bluetooth.png"}, {"name":"测试4","url":"/images/bluetooth.png"}, {"name":"测试5","url":"/images/bluetooth.png"}, {"name":"测试6","url":"/images/bluetooth.png"}, {"name":"测试7","url":"/images/bluetooth.png"}]}, ], itemWidth: wx.getSystemInfoSync().windowWidth / 4, scrollAreaHeight:wx.getSystemInfoSync().windowHeight - 44, float:false, curSelectTab:0, scrollToItem:null, scrollTop: 0, //到顶部的距离 listGroupHeight:0, }, onReady: function () { this.cacluItemHeight(); }, scroll:function(e){ console.log("scroll:",e); if(e.detail.scrollTop>=44){ this.setData({ float : true }) } else if(e.detail.scrollTop<44) { this.setData({ float : false }) } let scrollTop = e.detail.scrollTop; let current = this.data.curSelectTab; if (scrollTop >= this.distance) { //页面向上滑动 //列表当前可视区域最底部到顶部的距离 超过 当前列表选中项距顶部的高度(且没有下标越界),则更新tab栏 if (current + 1 < this.heightArr.length && scrollTop >= this.heightArr[current]) { this.setData({ curSelectTab: current + 1 }) } } else { //页面向下滑动 //如果列表当前可视区域最顶部到顶部的距离 小于 当前列表选中的项距顶部的高度,则切换tab栏的选中项 if (current - 1 >= 0 && scrollTop < this.heightArr[current - 1]) { this.setData({ curSelectTab: current - 1 }) } } //更新到顶部的距离 this.distance = scrollTop; }, tabClick(e){ this.setData({ curSelectTab: e.currentTarget.dataset.index, scrollToItem: "v_"+e.currentTarget.dataset.index }) }, //计算每一个item高度 cacluItemHeight() { let that = this; this.heightArr = []; let h = 0; const query = wx.createSelectorQuery(); query.selectAll('.list-group-item').boundingClientRect() query.exec(function(res) { res[0].forEach((item) => { h += item.height; that.heightArr.push(h); }) console.log(that.heightArr); that.setData({ listGroupHeight: that.heightArr[that.heightArr.length - 1 ] }) }) },})
在逻辑代码中最主要的有两个地方:
cacluItemHeight 计算列表中item的高度数组,并将最终计算的结果保存在 heightArr数组中。
heightArr数组中的每一项的值是在前一项的基础之上进行累加。
scroll 中判断当前的滚动方向,根据滚动判断当前的方向,然后根据滚动的距离设置当前选择的tab。
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