<template>
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<view class="">
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<view class="u-sticky-wrap" :class="[elClass]" :style="{
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height: fixed ? height + 'px' : 'auto',
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backgroundColor: bgColor
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}">
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<view class="u-sticky" :style="{
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position: fixed ? 'fixed' : 'static',
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top: stickyTop + 'px',
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left: left + 'px',
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width: width == 'auto' ? 'auto' : width + 'px',
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zIndex: uZIndex
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}">
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<slot></slot>
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</view>
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</view>
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</view>
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</template>
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<script>
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/**
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* sticky 吸顶
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* @description 该组件与CSS中position: sticky属性实现的效果一致，当组件达到预设的到顶部距离时， 就会固定在指定位置，组件位置大于预设的顶部距离时，会重新按照正常的布局排列。
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* @tutorial https://www.uviewui.com/components/sticky.html
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* @property {String Number} offset-top 吸顶时与顶部的距离，单位rpx（默认0）
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* @property {String Number} index 自定义标识，用于区分是哪一个组件
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* @property {Boolean} enable 是否开启吸顶功能（默认true）
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* @property {String} bg-color 组件背景颜色（默认#ffffff）
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* @property {String Number} z-index 吸顶时的z-index值（默认970）
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* @property {String Number} h5-nav-height 导航栏高度，自定义导航栏时(无导航栏时需设置为0)，需要传入此值，单位px（默认44）
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* @event {Function} fixed 组件吸顶时触发
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* @event {Function} unfixed 组件取消吸顶时触发
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* @example <u-sticky offset-top="200"><view>塞下秋来风景异，衡阳雁去无留意</view></u-sticky>
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*/
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export default {
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name: "u-sticky",
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props: {
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// 吸顶容器到顶部某个距离的时候，进行吸顶，在H5平台，NavigationBar为44px
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offsetTop: {
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type: [Number, String],
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default: 0
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},
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//列表中的索引值
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index: {
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type: [Number, String],
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default: ''
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},
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// 是否开启吸顶功能
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enable: {
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type: Boolean,
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default: true
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},
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// h5顶部导航栏的高度
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h5NavHeight: {
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type: [Number, String],
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default: 44
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},
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// 吸顶区域的背景颜色
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bgColor: {
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type: String,
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default: '#ffffff'
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},
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// z-index值
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zIndex: {
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type: [Number, String],
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default: ''
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}
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},
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data() {
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return {
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fixed: false,
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height: 'auto',
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stickyTop: 0,
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elClass: this.$u.guid(),
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left: 0,
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width: 'auto',
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};
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},
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watch: {
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offsetTop(val) {
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this.initObserver();
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},
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enable(val) {
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if (val == false) {
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this.fixed = false;
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this.disconnectObserver('contentObserver');
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} else {
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this.initObserver();
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}
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}
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},
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computed: {
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uZIndex() {
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return this.zIndex ? this.zIndex : this.$u.zIndex.sticky;
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}
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},
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mounted() {
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this.initObserver();
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},
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methods: {
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initObserver() {
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if (!this.enable) return;
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// #ifdef H5
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this.stickyTop = this.offsetTop != 0 ? uni.upx2px(this.offsetTop) + this.h5NavHeight : this.h5NavHeight;
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// #endif
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// #ifndef H5
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this.stickyTop = this.offsetTop != 0 ? uni.upx2px(this.offsetTop) : 0;
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// #endif
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this.disconnectObserver('contentObserver');
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this.$uGetRect('.' + this.elClass).then((res) => {
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this.height = res.height;
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this.left = res.left;
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this.width = res.width;
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this.$nextTick(() => {
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this.observeContent();
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});
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});
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},
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observeContent() {
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this.disconnectObserver('contentObserver');
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const contentObserver = this.createIntersectionObserver({
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thresholds: [0.95, 0.98, 1]
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});
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contentObserver.relativeToViewport({
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top: -this.stickyTop
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});
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contentObserver.observe('.' + this.elClass, res => {
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if (!this.enable) return;
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this.setFixed(res.boundingClientRect.top);
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});
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this.contentObserver = contentObserver;
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},
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setFixed(top) {
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const fixed = top < this.stickyTop;
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if (fixed) this.$emit('fixed', this.index);
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else if(this.fixed) this.$emit('unfixed', this.index);
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this.fixed = fixed;
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},
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disconnectObserver(observerName) {
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const observer = this[observerName];
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observer && observer.disconnect();
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},
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},
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beforeDestroy() {
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this.disconnectObserver('contentObserver');
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}
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};
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</script>
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<style scoped lang="scss">
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@import "../../libs/css/style.components.scss";
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.u-sticky {
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z-index: 9999999999;
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}
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</style>
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