<template>
  <div id="app">
  //外層包裹盒子
      <div
        class="infinite-list"
        v-infinite-scroll.loading.complated.immediate="load"
        style="overflow: auto"
        ref="infiniteList"
      >
        <ul>
          <li v-for="i in count" class="infinite-list-item">{{ i }}</li>
        </ul>
        //加載中
        <p v-if="loading && !complated" class="text">加載中...</p>
        //結(jié)束了
        <p v-if="complated" class="text">沒(méi)有更多了</p>
      </div>
    </div>
  </div>
</template>

<script>
import Velocity from "velocity-animate";
import { DatePicker } from "./components/DatePicker/index";
export default {
  name: "App",
  components: {
    DatePicker,
  },
  data() {
      count: 1,
      loading: false,
      complated: false,
    };
  },
  methods: {
  //滾動(dòng)到底部的處理邏輯
    load() {
      // 以下是定時(shí)器模擬異步數(shù)據(jù)請(qǐng)求，可根據(jù)自己的需求進(jìn)行變更
      this.loading = true;
      setTimeout(() => {
        if (this.count >= 15) {
          this.complated = true;
          return;
        }
        this.count += 3;
        this.loading = false;
      }, 1000);
    },
  },
};
</script>

<style lang="less">
#app {
  .infinite-list {
    height: 300px;
    width: 500px;
    border: 1px solid red;
    li {
      height: 50px;
      background: #e8f3fe;
      margin: 10px;
      color: #7dbcfc;
      text-align: center;
      line-height: 50px;
    }
    .text {
      color: green;
      text-align: center;
      line-height: 50px;
    }
  }
}
</style>

import { checkArriveBottom } from "./utils";
export default {
  install(Vue) {
    Vue.directive("infinite-scroll", {
      // 指令在插入的時(shí)候會(huì)執(zhí)行一次
      inserted: function (el, binding, vnode) {
        const fn = binding.value;
        const context = vnode.context;
        let timer = null;
        // 指令的值必須是一個(gè)函數(shù)，我們好執(zhí)行回調(diào)
        if (typeof fn != "function") {
          throw new Error("指令value必須為函數(shù)");
        }
        // 事件處理函數(shù)
        function handleScroll() {
          // 判斷滾動(dòng)條到達(dá)底部了，才開(kāi)始執(zhí)行回調(diào)
          if (checkArriveBottom(el)) {
            // 執(zhí)行回調(diào)的時(shí)候，要把this指向組件實(shí)例
            fn.bind(context)();
          }
        }
        // 將滾動(dòng)處理函數(shù)掛載到對(duì)應(yīng)組件實(shí)例上面，便于組件更新的時(shí)候，對(duì)設(shè)置了loading和complate屬性進(jìn)行移除事件綁定
        context.handleScroll = handleScroll;
        // 如果設(shè)置有immediate說(shuō)明立即執(zhí)行，則立即執(zhí)行回調(diào)，直到將內(nèi)容撐滿內(nèi)容區(qū)
        if (binding?.modifiers?.immediate) {
          timer = setInterval(() => {
            // 子元素的總高度大于設(shè)置指令的父級(jí)包裹元素就表示填滿了可視區(qū)，停止加載
            const childScrollHeight = el.firstElementChild.scrollHeight;
            if (childScrollHeight >= el.clientHeight) {
              return clearInterval(timer);
            }
            handleScroll();
          }, 1500);
        }
        // 綁定滾動(dòng)處理函數(shù)
        el.addEventListener("scroll", context.handleScroll);
      },
      //   組件更新的時(shí)候，會(huì)不斷觸發(fā)（最明顯就是data中的響應(yīng)式數(shù)據(jù)變化，會(huì)繼續(xù)執(zhí)行update方法）
      update(el, binding, vnode) {
        const context = vnode.context;
        // 如果加載中或者已經(jīng)加載完了，就移除滾動(dòng)事件
        if (
          (binding?.modifiers?.complated && context.complated) ||
          (binding?.modifiers?.loading && context.loading)
        ) {
          el.removeEventListener("scroll", context.handleScroll);
        } else {
          // 當(dāng)loading和complate都是false的時(shí)候，表示可以繼續(xù)加載
          el.addEventListener("scroll", context.handleScroll);
        }
      },
    });
  },
};

/**
 * @Description 用于判斷滾動(dòng)條是否到達(dá)底部
 * @param { Element }
 * @return { Boolean }
 **/
export function checkArriveBottom(el) {
  const clientHeight = el.clientHeight;
  const scrollTop = el.scrollTop;
  const scrollHeight = el.scrollHeight;
  //可以設(shè)置>=就行，這里也可以設(shè)置距離底部一定距離，自定義，不一定非要到達(dá)底部
  return clientHeight + scrollTop >= scrollHeight;
}

import Vue from "vue";
import App from "./App.vue";
import vInfiniteScroll from "./components/v-infinite-scroll";
Vue.use(vInfiniteScroll);
Vue.use(myUi);
new Vue({
  render: (h) => h(App),
}).$mount("#app");