isTabFixed: false,//是否吸顶
tab: 1,//当前tab
page: 1,//当前页数
listStatus: {
 finished: false,//是否已是最后一页
 loading: false,//是否加载中
},
items: [],//商品数组
tabMap: [],//tab列表数组
cache:{},//缓存
listName: '',//商品列表名称
tabName: '',//tab列表名称
apiName: '',//api方法名称
queryName: '',//api请求参数名称

_addCache(proList) {
 cache[this.tab] = {
 finished: this.listStatus.finished,
 page: this.page,
 list: proList,
 };
},

_getList(type) {
 let data = {};
 data[this.queryName] = this.tab;
 data.page = this.page;
 this.$http[this.apiName](data)
 .then((res) => {
 this.listStatus.finished = !res.has_more;//更新是否是最后一页的状态
 this._handleData(res.items);//处理得到的商品列表
 })
 .catch((err) => {
 note(err.message || '出错啦');
 });
},
_handleData(proList) {
 if (this.page === 1) {//表示是tab切换时请求的数据，所以直接将items的指向切换
 this.items = proList;
 } else {//因为是翻页，所以需要把数据拼接
 this.items = this.items.concat(proList);
 }
 this.$store.setData(this.listName, this.items);//把数据更新给父组件
 this._addCache(this.items);//把数据加入缓存
},

_loadmore() {
 this.page = this.page + 1;
 this._getList();
},

changeTab(id) {
 this.tab = id;
 this.$store.setData(this.tabName, this.tab);//将tab的指向同步给父组件
 this._scrollToTab();//视图回到顶部
 if (cache[this.tab]) {
 const target = cache[this.tab];
 this.listStatus.finished = target.finished;
 this.page = target.page;
 this.items = target.list;
 this.$store.setData(this.listName, this.items);//将商品列表同步给父组件
 } else {
 this.page = 1;
 this._getList();
 }
},
//视图回到顶部
_scrollToTab() {
 let scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
 let productsTop = this.$refs.products.$el.offsetTop;//商品列表距离顶部的距离
 let topHeight = this.$refs.tabNav.offsetHeight;//tab栏的高度
 if (scrollTop > productsTop) {
 window.scrollTo(0, productsTop - topHeight);
 }
},

handleNavFixed() {
 this.stickyTop = this.$store.getData('stickyTop') || 0;//吸顶的高度
 window.onscroll = (e) => {
 let top = document.documentElement.scrollTop || document.body.scrollTop;
 let tabHeight = this.$refs.tabNav.offsetTop - top - 1;
 if (tabHeight <= this.stickyTop && !this.isTabFixed) {//结合判断为了避免重复计算
 this.isTabFixed = true;
 }
 if (tabHeight >= this.stickyTop && this.isTabFixed) {
 this.isTabFixed = false;
 }
 };
},

//组件部分
init(data = {}) {
 this.listStatus.finished = !data.hasMore;
 this.tabName = data.tabName;
 this.listName = data.listName;
 this.apiName = data.apiName;
 this.queryName = data.queryName;
 this.handleNavFixed();//判断是否吸顶
},
//调用组件
this.$bus.emit('tab-list.init', {
 tabName: 'tab',
 listName: 'items',
 apiName: 'homeList',
 queryName: 'tab_id',
 hasMore: this.hasMore,
});