微信小程序中实现美团菜单的方法与步骤

onLoad(e) {

 let goodsList = this.data.goodsList;

 // 初始化每项菜品距离顶部的距离

 for (let i = 0; i < goodsList.length; i++) {

 if (i != 0)

 goodsList[i].scrollTop = parseInt(goodsList[i - 1].scrollTop) + parseInt((goodsList[i - 1].goods.length * 90) + 35)

 }

 this.data.goodsList = goodsList;

},

// 右侧滚动事件

onGoodsScroll: function (e) {

 let that = this;

 // 当前滚动部分距离页面顶部距离

 let scrollTop = parseInt(e.detail.scrollTop);

 let goodsList = that.data.goodsList;

 for (let i = 0; i < goodsList.length; i++) {

 let currentScrollTop = goodsList[i].scrollTop;

 let nextScrollTop = 0;

 if ((i + 1) == goodsList.length)

 nextScrollTop = goodsList[i].scrollTop;

 else

 nextScrollTop = goodsList[i + 1].scrollTop;

 if (currentScrollTop < scrollTop && scrollTop < nextScrollTop) {

 that.setData({

 classifyIdLeft: goodsList[i].id,

 classifySeleted: goodsList[i].id

 })

 }

 }

}

// 右侧滚动事件

 onGoodsScroll: function (e) {

 let that = this;

 let scale = e.detail.scrollWidth / 600;

 let scrollTop = e.detail.scrollTop / scale;

 let h = 0;

 let classifySeleted;

 let len = that.data.goodsList.length;

 that.data.goodsList.forEach(function (classify, i) {

 var _h = 70 + classify.goods.length * 180;

 if (scrollTop >= h - 100 / scale) {

 classifySeleted = classify.id;

 }

 h += _h;

 });

 that.setData({

 classifySeleted: classifySeleted,

 classifyIdLeft: classifySeleted,

 })

 },