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244 lines
17 KiB
244 lines
17 KiB
<template> |
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<view class="u-wrap" :style="{ |
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opacity: Number(opacity), |
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borderRadius: borderRadius + 'rpx', |
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// 因为time值需要改变,所以不直接用duration值(不能改变父组件prop传过来的值) |
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transition: `opacity ${time / 1000}s ease-in-out` |
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}" |
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:class="'u-lazy-item-' + elIndex"> |
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<view :class="'u-lazy-item-' + elIndex"> |
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<image :style="{borderRadius: borderRadius + 'rpx', height: imgHeight}" v-if="!isError" class="u-lazy-item" |
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:src="isShow ? image : loadingImg" :mode="imgMode" @load="imgLoaded" @error="loadError" @tap="clickImg"></image> |
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<image :style="{borderRadius: borderRadius + 'rpx', height: imgHeight}" class="u-lazy-item error" v-else :src="errorImg" |
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:mode="imgMode" @load="errorImgLoaded" @tap="clickImg"></image> |
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</view> |
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</view> |
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</template> |
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|
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<script> |
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/** |
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* lazyLoad 懒加载 |
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* @description 懒加载使用的场景为：页面有很多图片时，APP会同时加载所有的图片，导致页面卡顿，各个位置的图片出现前后不一致等. |
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* @tutorial https://www.uviewui.com/components/lazyLoad.html |
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* @property {String Number} index 用户自定义值，在事件触发时回调，用以区分是哪个图片 |
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* @property {String} image 图片路径 |
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* @property {String} loading-img 预加载时的占位图 |
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* @property {String} error-img 图片加载出错时的占位图 |
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* @property {String} threshold 触发加载时的位置，见上方说明，单位 rpx（默认300） |
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* @property {String Number} duration 图片加载成功时，淡入淡出时间，单位ms（默认） |
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* @property {String} effect 图片加载成功时，淡入淡出的css动画效果（默认ease-in-out） |
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* @property {Boolean} is-effect 图片加载成功时，是否启用淡入淡出效果（默认true） |
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* @property {String Number} border-radius 图片圆角值，单位rpx（默认0） |
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* @property {String Number} height 图片高度，注意：实际高度可能受img-mode参数影响（默认450） |
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* @property {String Number} mg-mode 图片的裁剪模式，详见image组件裁剪模式（默认widthFix） |
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* @event {Function} click 点击图片时触发 |
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* @event {Function} load 图片加载成功时触发 |
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* @event {Function} error 图片加载失败时触发 |
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* @example <u-lazy-load :image="image" :loading-img="loadingImg" :error-img="errorImg"></u-lazy-load> |
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*/ |
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export default { |
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name: 'u-lazy-load', |
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props: { |
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index: { |
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type: [Number, String] |
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}, |
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// 要显示的图片 |
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image: { |
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type: String, |
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default: '' |
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}, |
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// 图片裁剪模式 |
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imgMode: { |
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type: String, |
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default: 'widthFix' |
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}, |
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// 占位图片路径 |
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loadingImg: { |
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type: String, |
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default: 'data:image/png;base64,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' |
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}, |
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// 加载失败的错误占位图 |
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errorImg: { |
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type: String, |
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default: 'data:image/png;base64,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' |
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}, |
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// 图片进入可见区域前多少像素时，单位rpx，开始加载图片 |
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// 负数为图片超出屏幕底部多少距离后触发懒加载，正数为图片顶部距离屏幕底部多少距离时触发(图片还没出现在屏幕上) |
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threshold: { |
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type: [Number, String], |
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default: 100 |
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}, |
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// 淡入淡出动画的过渡时间 |
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duration: { |
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type: [Number, String], |
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default: 500 |
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}, |
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// 渡效果的速度曲线，各个之间差别不大，因为这是淡入淡出，且时间很短，不是那些变形或者移动的情况，会明显 |
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// linear|ease|ease-in|ease-out|ease-in-out|cubic-bezier(n,n,n,n); |
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effect: { |
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type: String, |
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default: 'ease-in-out' |
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}, |
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// 是否使用过渡效果 |
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isEffect: { |
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type: Boolean, |
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default: true |
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}, |
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// 圆角值 |
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borderRadius: { |
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type: [Number, String], |
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default: 0 |
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}, |
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// 图片高度，单位rpx |
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height: { |
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type: [Number, String], |
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default: '450' |
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} |
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}, |
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data() { |
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return { |
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isShow: false, |
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opacity: 1, |
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time: this.duration, |
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loadStatus: '', // 默认是懒加载中的状态 |
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isError: false, // 图片加载失败 |
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elIndex: this.$u.guid() |
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} |
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}, |
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computed: { |
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// 将threshold从rpx转为px |
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getThreshold() { |
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// 先取绝对值，因为threshold可能是负数，最后根据this.threshold是正数或者负数，重新还原 |
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let thresholdPx = uni.upx2px(Math.abs(this.threshold)); |
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return this.threshold < 0 ? -thresholdPx : thresholdPx; |
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}, |
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// 计算图片的高度，可能为auto，带%，或者直接数值 |
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imgHeight() { |
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return this.$u.addUnit(this.height); |
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} |
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}, |
|
created() { |
|
// 由于一些特殊原因，不能将此变量放到data中定义 |
|
this.observer = {}; |
|
}, |
|
watch: { |
|
isShow(nVal) { |
|
// 如果是不开启过渡效果，直接返回 |
|
if (!this.isEffect) return; |
|
this.time = 0; |
|
// 原来opacity为1(不透明，是为了显示占位图)，改成0(透明，意味着该元素显示的是背景颜色，默认的白色)，再改成1，是为了获得过渡效果 |
|
this.opacity = 0; |
|
// 延时30ms，否则在浏览器H5，过渡效果无效 |
|
setTimeout(() => { |
|
this.time = this.duration; |
|
this.opacity = 1; |
|
}, 30) |
|
}, |
|
// 图片路径发生变化时，需要重新标记一些变量，否则会一直卡在某一个状态，比如isError |
|
image(n) { |
|
if(!n) { |
|
// 如果传入null或者''，或者undefined，标记为错误状态 |
|
this.isError = true; |
|
} else { |
|
this.init(); |
|
this.isError = false; |
|
} |
|
} |
|
}, |
|
methods: { |
|
// 用于重新初始化 |
|
init() { |
|
this.isError = false; |
|
this.loadStatus = ''; |
|
}, |
|
// 点击图片触发的事件,loadlazy-还是懒加载中状态，loading-图片正在加载，loaded-图片加加载完成 |
|
clickImg() { |
|
let whichImg = ''; |
|
// 如果isShow为false，意味着图片还没开始加载，点击的只能是最开始的占位图 |
|
if (this.isShow == false) whichImg = 'lazyImg'; |
|
// 如果isError为true，意味着图片加载失败，这是只剩下错误的占位图，所以点击的只能是错误占位图 |
|
// 当然，也可以给错误的占位图元素绑定点击事件，看你喜欢~ |
|
else if (this.isError == true) whichImg = 'errorImg'; |
|
// 总共三张图片，除了两个占位图，剩下的只能是正常的那张图片了 |
|
else whichImg = 'realImg'; |
|
// 只通知当前图片的index |
|
this.$emit('click', this.index); |
|
}, |
|
// 图片加载完成事件，可能是加载占位图时触发，也可能是加载真正的图片完成时触发，通过isShow区分 |
|
imgLoaded() { |
|
// 占位图加载完成 |
|
if (this.loadStatus == '') { |
|
this.loadStatus = 'lazyed'; |
|
} |
|
// 真正的图片加载完成 |
|
else if (this.loadStatus == 'lazyed') { |
|
this.loadStatus = 'loaded'; |
|
this.$emit('load', this.index); |
|
} |
|
}, |
|
// 错误的图片加载完成 |
|
errorImgLoaded() { |
|
this.$emit('error', this.index); |
|
}, |
|
// 图片加载失败 |
|
loadError() { |
|
this.isError = true; |
|
}, |
|
disconnectObserver(observerName) { |
|
const observer = this[observerName]; |
|
observer && observer.disconnect(); |
|
}, |
|
}, |
|
beforeDestroy() { |
|
// 销毁页面时，可能还没触发某张很底部的懒加载图片，所以把这个事件给去掉 |
|
//observer.disconnect(); |
|
}, |
|
mounted() { |
|
// 此uOnReachBottom事件由mixin.js发出，目的是让页面到底时，保证所有图片都进行加载，做到绝对稳定且可靠 |
|
this.$nextTick(() => { |
|
uni.$once('uOnReachBottom', () => { |
|
if (!this.isShow) this.isShow = true; |
|
}); |
|
}) |
|
// mounted的时候，不一定挂载了这个元素，延时30ms，否则会报错或者不报错，但是也没有效果 |
|
setTimeout(() => { |
|
// 这里是组件内获取布局状态，不能用uni.createIntersectionObserver，而必须用this.createIntersectionObserver |
|
this.disconnectObserver('contentObserver'); |
|
const contentObserver = uni.createIntersectionObserver(this); |
|
// 要理解这里怎么计算的，请看这个： |
|
// https://blog.csdn.net/qq_25324335/article/details/83687695 |
|
contentObserver.relativeToViewport({ |
|
bottom: this.getThreshold, |
|
}).observe('.u-lazy-item-' + this.elIndex, (res) => { |
|
if (res.intersectionRatio > 0) { |
|
// 懒加载状态改变 |
|
this.isShow = true; |
|
// 如果图片已经加载，去掉监听，减少性能的消耗 |
|
this.disconnectObserver('contentObserver'); |
|
} |
|
}) |
|
this.contentObserver = contentObserver; |
|
}, 30) |
|
} |
|
} |
|
</script> |
|
|
|
<style scoped lang="scss"> |
|
@import "../../libs/css/style.components.scss"; |
|
|
|
.u-wrap { |
|
background-color: #eee; |
|
overflow: hidden; |
|
} |
|
|
|
.u-lazy-item { |
|
width: 100%; |
|
// 骗系统开启硬件加速 |
|
transform: transition3d(0, 0, 0); |
|
// 防止图片加载“闪一下” |
|
will-change: transform; |
|
/* #ifndef APP-NVUE */ |
|
display: block; |
|
/* #endif */ |
|
} |
|
</style>
|
|
|