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255 lines
17 KiB
255 lines
17 KiB
1 year ago
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<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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<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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emits: ["click", "load", "error"],
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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,iVBORw0KGgoAAAANSUhEUgAAAZAAAAGQCAMAAAC3Ycb+AAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAAyJpVFh0WE1MOmNvbS5hZG9iZS54bXAAAAAAADw/eHBhY2tldCBiZWdpbj0i77u/IiBpZD0iVzVNME1wQ2VoaUh6cmVTek5UY3prYzlkIj8+IDx4OnhtcG1ldGEgeG1sbnM6eD0iYWRvYmU6bnM6bWV0YS8iIHg6eG1wdGs9IkFkb2JlIFhNUCBDb3JlIDUuMy1jMDExIDY2LjE0NTY2MSwgMjAxMi8wMi8wNi0xNDo1NjoyNyAgICAgICAgIj4gPHJkZjpSREYgeG1sbnM6cmRmPSJodHRwOi8vd3d3LnczLm9yZy8xOTk5LzAyLzIyLXJkZi1zeW50YXgtbnMjIj4gPHJkZjpEZXNjcmlwdGlvbiByZGY6YWJvdXQ9IiIgeG1sbnM6eG1wPSJodHRwOi8vbnMuYWRvYmUuY29tL3hhcC8xLjAvIiB4bWxuczp4bXBNTT0iaHR0cDovL25zLmFkb2JlLmNvbS94YXAvMS4wL21tLyIgeG1sbnM6c3RSZWY9Imh0dHA6Ly9ucy5hZG9iZS5jb20veGFwLzEuMC9zVHlwZS9SZXNvdXJjZVJlZiMiIHhtcDpDcmVhdG9yVG9vbD0iQWRvYmUgUGhvdG9zaG9wIENTNiAoV2luZG93cykiIHhtcE1NOkluc3RhbmNlSUQ9InhtcC5paWQ6OUM0QjNBQjkyQUQ2MTFFQTlCNUQ4RTIzNDE5RUIxNjciIHhtcE1NOkRvY3VtZW50SUQ9InhtcC5kaWQ6OUM0QjNBQkEyQUQ2MTFFQTlCNUQ4RTIzNDE5RUIxNjciPiA8eG1wTU06RGVyaXZlZEZyb20gc3RSZWY6aW5zdGFuY2VJRD0ieG1wLmlpZDo5QzRCM0FCNzJBRDYxMUVBOUI1RDhFMjM0MTlFQjE2NyIgc3RSZWY6ZG9jdW1lbnRJRD0ieG1wLmRpZDo5QzRCM0FCODJBRDYxMUVBOUI1RDhFMjM0MTlFQjE2NyIvPiA8L3JkZjpEZXNjcmlwdGlvbj4gPC9yZGY6UkRGPiA8L3g6eG1wbWV0YT4gPD94cGFja2V0IGVuZD0iciI/PtRHfPcAAAAzUExURZWVldfX18PDw62trZubm9zc3Li4uKGhoebm5tLS0uHh4c3Nzaenp729vcjIyLKysuvr6141L40AAAcXSURBVHja7NzZlqpGAEBR5lG0//9rIw7IJKJi4or7PGTdtN10wr5SVAEGf/qqArsAiIAAERAgAgJEQIAIiIAAERAgAgJEQIAIiIAAERAgAgJEQIAIiIAAERAgAgJEQIAIiIAAERAgAgJEQIAIiIAAERAgAgJEQIAIiIAAERAgAgJEQIAIiIAAERAgAgJEQIAIiIAAERAgAgJEQIAIiIAAERAgAgJEQIAICBABERAgAgJEQIAICBABERAgAgJEQIAICBABERAgAgJEQIAICBABERAgAgJEQIAICBABERAgAgJEQIAICBABERAgAgJEQIAICBABERAgAgJEQIAICBABERAgAgJEQIAICBABERAg+nmQFMi5Jis+sIniED23jSzIgLTtg2D//iYme/8QBM/9lQ+CAEhbNLM3N9hEHAThX7GPCiBfAxK1b51kD+R7QMLjXg7iCsgWIPUh7pfVozG791oeBPngm48G583uW5GkBvI+SBaM2xXDn1oqum423bX/mgF5FySc2cv93Voug9TdZotsggnkBZB2NzbhrSY5HnoG07jei8dvzsJB/c3W60SALILE46+WCztsbhPR7R2VJq0ukEcT49nyy8QhaKcRa3fYHZD4+ufqOJAcgDz8/59vtw1I3QP5K6JsOG0vm3hce4I8LQp/BaRZGJC3AAn7IKOKXbC+7EdA5vdmmVwOLksgRThqOqiH4XEGsht+peoPUE8U/jJIO5OLH4GEwUslV5G0PTBG5Uiw/Y2jyigO3l9HAHKv9PYb82LloH74dZBoBUgar+l48NsNvtD0fkez9iwrAvIYZDRCl+Xs149Hm/KZmQ+QjUCiO1ei4ru7EsgnQYrkznlQb7thCuRfAzlOAPN72427P4VA/i2Q/DKT/Ls/VR8fvIBsDZIuz7TPF6TCbnk4GJkB2RokejTjuE7/unlgCuSTIO0Cy+Plp6vDfnQlBchy8QtjSHVd3EgmK1bHLm+H6+nXYbz2DuQRSPnqoL7vvq0u70on4zvxgCyWD3b9UyDVdW24PaWaiGTnFZJwPIQAebDpIKheBIm7n124ZthMJipAlkqHO+IZkP1tbfzOJark/A7MgKyvvl60fRqkvXfhuow+t9+q00+0/yyBrK8ZngOtBzldhw2X9tvpNGty0gvkmbPeJ0Cy/r09s/stbmfo0yMWkEdjevgKyOn2t2pxv7UXoibTdCDLje9/Ww1ymqzn87dbp92242ZmMRjI8hASvwKSLq4udqN6ksw8nxXN3tszD9L8Gkg+2mFrQYql5az4tvFj5xOx4VwnSdeBtGdyPwUytxK77pBVlNHdO7OK3rh/eTPUvdutT3fO52tuHMqD4N7llv8pyOQQ//w19YVDfX27+Sfuby9/6nau4pdA8vEdOZuChEH/quHt0Jg+IRJ/5+PrHwKZXfjbDiS73Zo7mu5UkzX7uTsXe0e/7nC3ePf1O69+BUg2XDfZCqSqOu7rGVf8cHBe8zhC2b61dtUHXv0OkGo6ZL4JkpbRYXdUaFevivx2M/1GIOctNh949TtAoumQ+TpIHMX54CJu+8BDd8FkE5BqcZh/59XvAClmTvKfB0nDqIlHo3T70SftyW1eX9dXtgQJqs1f/Q6QaOa/7wmQKtxH8eiGoCRuovODIO3VxOMmruZbHrLyD7z6DSDtGyT7ew1kf9hNn07c986JTovzzem0Id9wUG+Vk/IDr34DSNR7huZJkMFT6vEhqrPx/j5cnlZML8N6/PAzh9Y99Flm5Yde/c9BquDOkvkKkMP58dA4qi9vivE8JOvGz/j8FokfPpr288+pH2ZPOZrLmeGD+7KOh6dqYWJ48ki7yUg0tz0go/fv/LLddfV3sgOLJyaGPY/zrSlh1a36Arkzoue9CyG35ze6E6/dzO2Ga0EGHqdRJIkfn9/8OEjTW8Vq91ZWh39FeehWA7Nu9ft8CpUEk1WWOyDF0OPyEU2Pnzf/bZC0P6IPzmAvu7KauQBVrgKpJ0tG2arHzX8e5Pb3PezNs/PrX+3JMyCLn9XXf37tPFHvt09WfCDDjx+yyn1/p1V11j7GnB/q3leLuVva79S/tzed+db08YpF4uOZtmz/9oXWMq6BCAgQAQEiIEAERECACAgQAQEiIEAERECACAgQAQEiIEAERECACAgQAQEiIEAERECACAgQAQEiIEAERECACAgQAQEiIEAERECACAgQAQEiIEAERECACAgQAQEiIEAERECACAgQAQEiIEAERECACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiACAgQAQEiIEAEBIiAALELvqt/BBgACqVeUBXxcCkAAAAASUVORK5CYII='
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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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// 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
|
||
|
|
borderRadius: {
|
||
|
|
type: [Number, String],
|
||
|
|
default: 0
|
||
|
|
},
|
||
|
|
// 图片高度，单位rpx
|
||
|
|
height: {
|
||
|
|
type: [Number, String],
|
||
|
|
default: '450'
|
||
|
|
}
|
||
|
|
},
|
||
|
|
data() {
|
||
|
|
return {
|
||
|
|
isShow: false,
|
||
|
|
opacity: 1,
|
||
|
|
time: this.duration,
|
||
|
|
loadStatus: '', // 默认是懒加载中的状态
|
||
|
|
isError: false, // 图片加载失败
|
||
|
|
elIndex: this.$u.guid()
|
||
|
|
}
|
||
|
|
},
|
||
|
|
computed: {
|
||
|
|
// 将threshold从rpx转为px
|
||
|
|
getThreshold() {
|
||
|
|
// 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
|
||
|
|
let thresholdPx = uni.upx2px(Math.abs(this.threshold));
|
||
|
|
return this.threshold < 0 ? -thresholdPx : thresholdPx;
|
||
|
|
},
|
||
|
|
// 计算图片的高度，可能为auto，带%，或者直接数值
|
||
|
|
imgHeight() {
|
||
|
|
return this.$u.addUnit(this.height);
|
||
|
|
}
|
||
|
|
},
|
||
|
|
created() {
|
||
|
|
// 由于一些特殊原因，不能将此变量放到data中定义
|
||
|
|
this.observer = {};
|
||
|
|
},
|
||
|
|
watch: {
|
||
|
|
isShow(nVal) {
|
||
|
|
// 如果是不开启过渡效果，直接返回
|
||
|
|
if (!this.isEffect) return;
|
||
|
|
this.time = 0;
|
||
|
|
// 原来opacity为1(不透明，是为了显示占位图)，改成0(透明，意味着该元素显示的是背景颜色，默认的白色)，再改成1，是为了获得过渡效果
|
||
|
|
this.opacity = 0;
|
||
|
|
// 延时30ms，否则在浏览器H5，过渡效果无效
|
||
|
|
setTimeout(() => {
|
||
|
|
this.time = this.duration;
|
||
|
|
this.opacity = 1;
|
||
|
|
}, 30)
|
||
|
|
},
|
||
|
|
// 图片路径发生变化时，需要重新标记一些变量，否则会一直卡在某一个状态，比如isError
|
||
|
|
image(n) {
|
||
|
|
if(!n) {
|
||
|
|
// 如果传入null或者''，或者undefined，标记为错误状态
|
||
|
|
this.isError = true;
|
||
|
|
} else {
|
||
|
|
this.init();
|
||
|
|
this.isError = false;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
},
|
||
|
|
methods: {
|
||
|
|
// 用于重新初始化
|
||
|
|
init() {
|
||
|
|
this.isError = false;
|
||
|
|
this.loadStatus = '';
|
||
|
|
},
|
||
|
|
// 点击图片触发的事件,loadlazy-还是懒加载中状态，loading-图片正在加载，loaded-图片加加载完成
|
||
|
|
clickImg() {
|
||
|
|
let whichImg = '';
|
||
|
|
// 如果isShow为false，意味着图片还没开始加载，点击的只能是最开始的占位图
|
||
|
|
if (this.isShow == false) whichImg = 'lazyImg';
|
||
|
|
// 如果isError为true，意味着图片加载失败，这是只剩下错误的占位图，所以点击的只能是错误占位图
|
||
|
|
// 当然，也可以给错误的占位图元素绑定点击事件，看你喜欢~
|
||
|
|
else if (this.isError == true) whichImg = 'errorImg';
|
||
|
|
// 总共三张图片，除了两个占位图，剩下的只能是正常的那张图片了
|
||
|
|
else whichImg = 'realImg';
|
||
|
|
// 只通知当前图片的index
|
||
|
|
this.$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();
|
||
|
|
},
|
||
|
|
},
|
||
|
|
// #ifndef VUE3
|
||
|
|
// 组件销毁前，将实例从u-form的缓存中移除
|
||
|
|
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();
|
||
|
|
},
|
||
|
|
// #endif
|
||
|
|
|
||
|
|
// #ifdef VUE3
|
||
|
|
beforeUnmount() {
|
||
|
|
|
||
|
|
},
|
||
|
|
// #endif
|
||
|
|
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>
|