詳解vue mint-ui源碼解析之loadmore組件

<div id="app">
 <mt-loadmore :top-method="loadTop" :bottom-method="loadBottom" :bottom-all-loaded="allLoaded" :max-distance="150"
 @top-status-change="handleTopChange" ref="loadmore">

 <div slot="top" class="mint-loadmore-top">
 <span v-show="topStatus === 'pull'" :class="{ 'rotate': topStatus === 'drop' }">↓</span>
 <span v-show="topStatus === 'loading'">Loading...</span>
 <span v-show="topStatus === 'drop'">釋放更新</span>
 </div>

 <ul class="scroll-wrapper">
 <li v-for="item in list" @click="itemClick(item)">{{ item }}</li>
 </ul>

 </mt-loadmore>
</div>

<link rel="stylesheet"  rel="external nofollow" >
*{
 margin: 0;
 padding: 0;
}
html, body{
 height: 100%;
}

#app{

 height: 100%;
 overflow: scroll;
}
.scroll-wrapper{
 margin: 0;
 padding: 0;
 list-style: none;

}
.scroll-wrapper li{
 line-height: 120px;
 font-size: 60px;
 text-align: center;
}

<!-- 先引入 Vue -->
<script src="https://unpkg.com/vue/dist/vue.js"></script>
<!-- 引入組件庫 -->
<script src="https://unpkg.com/mint-ui/lib/index.js"></script>
<script>
 new Vue({
 el: '#app',
 data: {
 list: [],
 allLoaded: false,
 topStatus: ''
 },
 created: function () {
 var i =0, len=20;
 for (; i< len; i++){
 this.list.push('demo' + i);
 }

 },
 methods: {
 loadTop: function () { // 刷新數(shù)據(jù)的操作
 var self = this;
 setTimeout(function () {
 self.list.splice(0, self.list.length);
 var i =0, len=20;
 for (; i< len; i++){
 self.list.push('demo' + i);
 }
 self.$refs.loadmore.onTopLoaded();
 }, 2000);
 },
 loadBottom: function () { // 加載更多數(shù)據(jù)的操作
 //load data

 //this.allLoaded = true;// 若數(shù)據(jù)已全部獲取完畢
 var self = this;
 setTimeout(function () {
 var i =0; len = 10;
 for (; i< len; i++){
 self.list.push('dddd' + i);
 }
 self.$refs.loadmore.onBottomLoaded();
 }, 2000);

 },
 handleTopChange: function (status) {
 this.topStatus = status;
 },
 itemClick: function (data) {
 console.log('item click, msg : ' + data);
 }
 }
 });
</script>

 <div class="mint-loadmore">
 <div class="mint-loadmore-content" :class="{ 'is-dropped': topDropped || bottomDropped}" :style="{ 'transform': 'translate3d(0, ' + translate + 'px, 0)' }">
 <slot name="top">
 <div class="mint-loadmore-top" v-if="topMethod">
 <spinner v-if="topStatus === 'loading'" class="mint-loadmore-spinner" :size="20" type="fading-circle"></spinner>
 <span class="mint-loadmore-text">{{ topText }}</span>
 </div>
 </slot>
 <slot></slot>
 <slot name="bottom">
 <div class="mint-loadmore-bottom" v-if="bottomMethod">
 <spinner v-if="bottomStatus === 'loading'" class="mint-loadmore-spinner" :size="20" type="fading-circle"></spinner>
 <span class="mint-loadmore-text">{{ bottomText }}</span>
 </div>
 </slot>
 </div>
 </div>

data() {
 return {
 translate: 0, // 此變量決定當(dāng)前組件上下移動,
 scrollEventTarget: null, // 滾動的dom節(jié)點(diǎn)
 containerFilled: false, // 當(dāng)前滾動的內(nèi)容是否填充完整,不完成會調(diào)用 loadmore的回調(diào)函數(shù)
 topText: '', // 下拉刷新,顯示的文本
 topDropped: false, // 記錄當(dāng)前drop狀態(tài),用給組件dom添加is-dropped class(添加回到原點(diǎn)的動畫)
 bottomText: '', // 上拉加載更多 顯示的文本
 bottomDropped: false, // 同topDropped
 bottomReached: false, // 當(dāng)前滾動是否滾動到了底部
 direction: '', // touch-move過程中, 當(dāng)前滑動的方向
 startY: 0, // touch-start 起始的y的坐標(biāo)值
 startScrollTop: 0, // touch-start 起始的滾動dom的 scrollTop
 currentY: 0, // touch-move 過程中的 y的坐標(biāo)
 topStatus: '', // 下拉刷新的狀態(tài): pull(下拉) drop(釋放) loading(正在加載數(shù)據(jù))
 bottomStatus: '' // 上拉加載更多的狀態(tài): 狀態(tài)同上
 };
}

watch: {
 topStatus(val) {
 this.$emit('top-status-change', val);
 switch (val) {
 case 'pull':
 this.topText = this.topPullText;
 break;
 case 'drop':
 this.topText = this.topDropText;
 break;
 case 'loading':
 this.topText = this.topLoadingText;
 break;
 }
 },

 bottomStatus(val) {
 this.$emit('bottom-status-change', val);
 switch (val) {
 case 'pull':
 this.bottomText = this.bottomPullText;
 break;
 case 'drop':
 this.bottomText = this.bottomDropText;
 break;
 case 'loading':
 this.bottomText = this.bottomLoadingText;
 break;
 }
 }
}

mounted() {
 this.init();// 當(dāng)前 vue component掛載完成之后, 執(zhí)行init()函數(shù)
}

init() {
 this.topStatus = 'pull';
 this.bottomStatus = 'pull';
 this.topText = this.topPullText;
 this.scrollEventTarget = this.getScrollEventTarget(this.$el); // 獲取滾動的dom節(jié)點(diǎn)
 if (typeof this.bottomMethod === 'function') {
 this.fillContainer(); // 判斷當(dāng)前滾動內(nèi)容是否填滿,沒有執(zhí)行外部傳入的loadmore回調(diào)函數(shù)加載數(shù)據(jù)
 this.bindTouchEvents(); // 為當(dāng)前組件dom注冊touch事件
 }
 if (typeof this.topMethod === 'function') {
 this.bindTouchEvents();
 }
 },

 fillContainer() {
 if (this.autoFill) {
 this.$nextTick(() => {
 if (this.scrollEventTarget === window) {
 this.containerFilled = this.$el.getBoundingClientRect().bottom >=
 document.documentElement.getBoundingClientRect().bottom;
 } else {
 this.containerFilled = this.$el.getBoundingClientRect().bottom >=
 this.scrollEventTarget.getBoundingClientRect().bottom;
 }
 if (!this.containerFilled) { // 如果沒有填滿內(nèi)容, 執(zhí)行l(wèi)oadmore的操作
 this.bottomStatus = 'loading';
 this.bottomMethod();// 調(diào)用外部的loadmore函數(shù),加載更多數(shù)據(jù)
 }
 });
 }
 }

 handleTouchStart(event) {
 this.startY = event.touches[0].clientY; // 手指按下的位置, 用于下面move事件計算手指移動的距離
 this.startScrollTop = this.getScrollTop(this.scrollEventTarget); // 起始scroll dom的 scrollTop(滾動的距離)
 //下面重置狀態(tài)變量
 this.bottomReached = false;
 if (this.topStatus !== 'loading') {
 this.topStatus = 'pull';
 this.topDropped = false;
 }
 if (this.bottomStatus !== 'loading') {
 this.bottomStatus = 'pull';
 this.bottomDropped = false;
 }
 }

 handleTouchMove(event) {
 //確保當(dāng)前touch節(jié)點(diǎn)的y的位置,在當(dāng)前l(fā)oadmore組件的內(nèi)部
 if (this.startY < this.$el.getBoundingClientRect().top && this.startY > this.$el.getBoundingClientRect().bottom) {
 return;
 }
 this.currentY = event.touches[0].clientY;
 let distance = (this.currentY - this.startY) / this.distanceIndex;
 this.direction = distance > 0 ? 'down' : 'up';
 // 下拉刷新,條件(1.外部傳入了刷新的回調(diào)函數(shù) 2.滑動方向是向下的 3.當(dāng)前滾動節(jié)點(diǎn)的scrollTop為0 4.當(dāng)前topStatus不是loading)
 if (typeof this.topMethod === 'function' && this.direction === 'down' &&
 this.getScrollTop(this.scrollEventTarget) === 0 && this.topStatus !== 'loading') {
 event.preventDefault();
 event.stopPropagation();
 //計算translate(將要平移的距離), 如果當(dāng)前移動的距離大于設(shè)置的最大距離,那么此次這次移動就不起作用了
 if (this.maxDistance > 0) {
 this.translate = distance <= this.maxDistance ? distance - this.startScrollTop : this.translate;
 } else {
 this.translate = distance - this.startScrollTop;
 }
 if (this.translate < 0) {
 this.translate = 0;
 }
 this.topStatus = this.translate >= this.topDistance ? 'drop' : 'pull';// drop: 到達(dá)指定的閾值,可以執(zhí)行刷新操作了
 }

 // 上拉操作, 判斷當(dāng)前scroll dom是否滾動到了底部
 if (this.direction === 'up') {
 this.bottomReached = this.bottomReached || this.checkBottomReached();
 }
 if (typeof this.bottomMethod === 'function' && this.direction === 'up' &&
 this.bottomReached && this.bottomStatus !== 'loading' && !this.bottomAllLoaded) {
 event.preventDefault();
 event.stopPropagation();
 // 判斷的邏輯思路同上
 if (this.maxDistance > 0) {
 this.translate = Math.abs(distance) <= this.maxDistance
 ? this.getScrollTop(this.scrollEventTarget) - this.startScrollTop + distance : this.translate;
 } else {
 this.translate = this.getScrollTop(this.scrollEventTarget) - this.startScrollTop + distance;
 }
 if (this.translate > 0) {
 this.translate = 0;
 }
 this.bottomStatus = -this.translate >= this.bottomDistance ? 'drop' : 'pull';
 }
 this.$emit('translate-change', this.translate);
 }

 checkBottomReached() {
 if (this.scrollEventTarget === window) {
 return document.body.scrollTop + document.documentElement.clientHeight >= document.body.scrollHeight;
 } else {
 return this.$el.getBoundingClientRect().bottom <= this.scrollEventTarget.getBoundingClientRect().bottom + 1;
 }
 }

 handleTouchEnd() {
 if (this.direction === 'down' && this.getScrollTop(this.scrollEventTarget) === 0 && this.translate > 0) {
 this.topDropped = true; // 為當(dāng)前組件添加 is-dropped class(也就是添加動畫處理)
 if (this.topStatus === 'drop') { // 到達(dá)了loading的狀態(tài)
 this.translate = '50'; // top slot的高度
 this.topStatus = 'loading';
 this.topMethod(); // 執(zhí)行回調(diào)函數(shù)
 } else { // 沒有到達(dá),回調(diào)原點(diǎn)
 this.translate = '0';
 this.topStatus = 'pull';
 }
 }
 // 處理邏輯同上
 if (this.direction === 'up' && this.bottomReached && this.translate < 0) {
 this.bottomDropped = true;
 this.bottomReached = false;
 if (this.bottomStatus === 'drop') {
 this.translate = '-50';
 this.bottomStatus = 'loading';
 this.bottomMethod();
 } else {
 this.translate = '0';
 this.bottomStatus = 'pull';
 }
 }
 this.$emit('translate-change', this.translate);
 this.direction = '';
 }
}