uview-ui/components/u-lazy-load/u-lazy-load.vue - dali_platform/mobile - Gitiles

 <template>
 	<view class="u-wrap" :style="{
 			  opacity: Number(opacity),
 			  borderRadius: borderRadius + 'rpx',
 			  // 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)
 			  transition: `opacity ${time / 1000}s ease-in-out`
 		   }"
 	 :class="'u-lazy-item-' + elIndex">
 		<view :class="'u-lazy-item-' + elIndex">
 			<image :style="{borderRadius: borderRadius + 'rpx', height: imgHeight}" v-if="!isError" class="u-lazy-item"
 			 :src="isShow ? image : loadingImg" :mode="imgMode" @load="imgLoaded" @error="loadError" @tap="clickImg"></image>
 			<image :style="{borderRadius: borderRadius + 'rpx', height: imgHeight}" class="u-lazy-item error" v-else :src="errorImg"
 			 :mode="imgMode" @load="errorImgLoaded" @tap="clickImg"></image>
 		</view>
 	</view>
 </template>

 <script>
 	/**
 	 * lazyLoad 懒加载
 	 * @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.
 	 * @tutorial https://www.uviewui.com/components/lazyLoad.html
 	 * @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
 	 * @property {String} image 图片路径
 	 * @property {String} loading-img 预加载时的占位图
 	 * @property {String} error-img 图片加载出错时的占位图
 	 * @property {String} threshold 触发加载时的位置，见上方说明，单位 rpx（默认300）
 	 * @property {String Number} duration 图片加载成功时，淡入淡出时间，单位ms（默认）
 	 * @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）
 	 * @property {Boolean} is-effect 图片加载成功时，是否启用淡入淡出效果（默认true）
 	 * @property {String Number} border-radius 图片圆角值，单位rpx（默认0）
 	 * @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）
 	 * @property {String Number} mg-mode 图片的裁剪模式，详见image组件裁剪模式（默认widthFix）
 	 * @event {Function} click 点击图片时触发
 	 * @event {Function} load 图片加载成功时触发
 	 * @event {Function} error 图片加载失败时触发
 	 * @example <u-lazy-load :image="image" :loading-img="loadingImg" :error-img="errorImg"></u-lazy-load>
 	 */
 	export default {
 		name: 'u-lazy-load',
 		props: {
 			index: {
 				type: [Number, String]
 			},
 			// 要显示的图片
 			image: {
 				type: String,
 				default: ''
 			},
 			// 图片裁剪模式
 			imgMode: {
 				type: String,
 				default: 'widthFix'
 			},
 			// 占位图片路径
 			loadingImg: {
 				type: String,
 				default: 'data:image/png;base64,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'
 			},
 			// 加载失败的错误占位图
 			errorImg: {
 				type: String,
 				default: 'data:image/png;base64,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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
 			// 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)
 			threshold: {
 				type: [Number, String],
 				default: 100
 			},
 			// 淡入淡出动画的过渡时间
 			duration: {
 				type: [Number, String],
 				default: 500
 			},
 			// 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
 			// linear|ease|ease-in|ease-out|ease-in-out|cubic-bezier(n,n,n,n);
 			effect: {
 				type: String,
 				default: 'ease-in-out'
 			},
 			// 是否使用过渡效果
 			isEffect: {
 				type: Boolean,
 				default: true
 			},
 			// 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.$emit('error', this.index);
 			},
 			// 图片加载失败
 			loadError() {
 				this.isError = true;
 			},
 			disconnectObserver(observerName) {
 				const observer = this[observerName];
 				observer && observer.disconnect();
 			},
 		},
 		beforeDestroy() {
 			// 销毁页面时，可能还没触发某张很底部的懒加载图片，所以把这个事件给去掉
 			//observer.disconnect();
 		},
 		mounted() {
 			// 此uOnReachBottom事件由mixin.js发出，目的是让页面到底时，保证所有图片都进行加载，做到绝对稳定且可靠
 			this.$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>
	<template>
	<view class="u-wrap" :style="{
	opacity: Number(opacity),
	borderRadius: borderRadius + 'rpx',
	// 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)
	transition: `opacity ${time / 1000}s ease-in-out`
	}"
	:class="'u-lazy-item-' + elIndex">
	<view :class="'u-lazy-item-' + elIndex">
	<image :style="{borderRadius: borderRadius + 'rpx', height: imgHeight}" v-if="!isError" class="u-lazy-item"
	:src="isShow ? image : loadingImg" :mode="imgMode" @load="imgLoaded" @error="loadError" @tap="clickImg"></image>
	<image :style="{borderRadius: borderRadius + 'rpx', height: imgHeight}" class="u-lazy-item error" v-else :src="errorImg"
	:mode="imgMode" @load="errorImgLoaded" @tap="clickImg"></image>
	</view>
	</view>
	</template>

	<script>
	/**
	* lazyLoad 懒加载
	* @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.
	* @tutorial https://www.uviewui.com/components/lazyLoad.html
	* @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
	* @property {String} image 图片路径
	* @property {String} loading-img 预加载时的占位图
	* @property {String} error-img 图片加载出错时的占位图
	* @property {String} threshold 触发加载时的位置，见上方说明，单位 rpx（默认300）
	* @property {String Number} duration 图片加载成功时，淡入淡出时间，单位ms（默认）
	* @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）
	* @property {Boolean} is-effect 图片加载成功时，是否启用淡入淡出效果（默认true）
	* @property {String Number} border-radius 图片圆角值，单位rpx（默认0）
	* @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）
	* @property {String Number} mg-mode 图片的裁剪模式，详见image组件裁剪模式（默认widthFix）
	* @event {Function} click 点击图片时触发
	* @event {Function} load 图片加载成功时触发
	* @event {Function} error 图片加载失败时触发
	* @example <u-lazy-load :image="image" :loading-img="loadingImg" :error-img="errorImg"></u-lazy-load>
	*/
	export default {
	name: 'u-lazy-load',
	props: {
	index: {
	type: [Number, String]
	},
	// 要显示的图片
	image: {
	type: String,
	default: ''
	},
	// 图片裁剪模式
	imgMode: {
	type: String,
	default: 'widthFix'
	},
	// 占位图片路径
	loadingImg: {
	type: String,
	default: 'data:image/png;base64,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'
	},
	// 加载失败的错误占位图
	errorImg: {
	type: String,
	default: 'data:image/png;base64,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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
	// 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)
	threshold: {
	type: [Number, String],
	default: 100
	},
	// 淡入淡出动画的过渡时间
	duration: {
	type: [Number, String],
	default: 500
	},
	// 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
	// linear\|ease\|ease-in\|ease-out\|ease-in-out\|cubic-bezier(n,n,n,n);
	effect: {
	type: String,
	default: 'ease-in-out'
	},
	// 是否使用过渡效果
	isEffect: {
	type: Boolean,
	default: true
	},
	// 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.$emit('error', this.index);
	},
	// 图片加载失败
	loadError() {
	this.isError = true;
	},
	disconnectObserver(observerName) {
	const observer = this[observerName];
	observer && observer.disconnect();
	},
	},
	beforeDestroy() {
	// 销毁页面时，可能还没触发某张很底部的懒加载图片，所以把这个事件给去掉
	//observer.disconnect();
	},
	mounted() {
	// 此uOnReachBottom事件由mixin.js发出，目的是让页面到底时，保证所有图片都进行加载，做到绝对稳定且可靠
	this.$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>