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2 лет назад
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  1. <template>
  2. <view class="u-wrap" :style="{
  3. opacity: Number(opacity),
  4. borderRadius: borderRadius + 'rpx',
  5. // 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)
  6. transition: `opacity ${time / 1000}s ease-in-out`
  7. }"
  8. :class="'u-lazy-item-' + elIndex">
  9. <view :class="'u-lazy-item-' + elIndex">
  10. <image :style="{borderRadius: borderRadius + 'rpx', height: imgHeight}" v-if="!isError" class="u-lazy-item"
  11. :src="isShow ? image : loadingImg" :mode="imgMode" @load="imgLoaded" @error="loadError" @tap="clickImg"></image>
  12. <image :style="{borderRadius: borderRadius + 'rpx', height: imgHeight}" class="u-lazy-item error" v-else :src="errorImg"
  13. :mode="imgMode" @load="errorImgLoaded" @tap="clickImg"></image>
  14. </view>
  15. </view>
  16. </template>
  17. <script>
  18. /**
  19. * lazyLoad 懒加载
  20. * @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.
  21. * @tutorial https://www.uviewui.com/components/lazyLoad.html
  22. * @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
  23. * @property {String} image 图片路径
  24. * @property {String} loading-img 预加载时的占位图
  25. * @property {String} error-img 图片加载出错时的占位图
  26. * @property {String} threshold 触发加载时的位置,见上方说明,单位 rpx(默认300)
  27. * @property {String Number} duration 图片加载成功时,淡入淡出时间,单位ms(默认)
  28. * @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)
  29. * @property {Boolean} is-effect 图片加载成功时,是否启用淡入淡出效果(默认true)
  30. * @property {String Number} border-radius 图片圆角值,单位rpx(默认0)
  31. * @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)
  32. * @property {String Number} mg-mode 图片的裁剪模式,详见image组件裁剪模式(默认widthFix)
  33. * @event {Function} click 点击图片时触发
  34. * @event {Function} load 图片加载成功时触发
  35. * @event {Function} error 图片加载失败时触发
  36. * @example <u-lazy-load :image="image" :loading-img="loadingImg" :error-img="errorImg"></u-lazy-load>
  37. */
  38. export default {
  39. name: 'u-lazy-load',
  40. props: {
  41. index: {
  42. type: [Number, String]
  43. },
  44. // 要显示的图片
  45. image: {
  46. type: String,
  47. default: ''
  48. },
  49. // 图片裁剪模式
  50. imgMode: {
  51. type: String,
  52. default: 'widthFix'
  53. },
  54. // 占位图片路径
  55. loadingImg: {
  56. type: String,
  57. default: 'data:image/png;base64,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'
  58. },
  59. // 加载失败的错误占位图
  60. errorImg: {
  61. type: String,
  62. default: 'data:image/png;base64,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'
  63. },
  64. // 图片进入可见区域前多少像素时,单位rpx,开始加载图片
  65. // 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)
  66. threshold: {
  67. type: [Number, String],
  68. default: 100
  69. },
  70. // 淡入淡出动画的过渡时间
  71. duration: {
  72. type: [Number, String],
  73. default: 500
  74. },
  75. // 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
  76. // linear|ease|ease-in|ease-out|ease-in-out|cubic-bezier(n,n,n,n);
  77. effect: {
  78. type: String,
  79. default: 'ease-in-out'
  80. },
  81. // 是否使用过渡效果
  82. isEffect: {
  83. type: Boolean,
  84. default: true
  85. },
  86. // 圆角值
  87. borderRadius: {
  88. type: [Number, String],
  89. default: 0
  90. },
  91. // 图片高度,单位rpx
  92. height: {
  93. type: [Number, String],
  94. default: '450'
  95. }
  96. },
  97. data() {
  98. return {
  99. isShow: false,
  100. opacity: 1,
  101. time: this.duration,
  102. loadStatus: '', // 默认是懒加载中的状态
  103. isError: false, // 图片加载失败
  104. elIndex: this.$u.guid()
  105. }
  106. },
  107. computed: {
  108. // 将threshold从rpx转为px
  109. getThreshold() {
  110. // 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
  111. let thresholdPx = uni.upx2px(Math.abs(this.threshold));
  112. return this.threshold < 0 ? -thresholdPx : thresholdPx;
  113. },
  114. // 计算图片的高度,可能为auto,带%,或者直接数值
  115. imgHeight() {
  116. return this.height == 'auto' ? 'auto' : String(this.height).indexOf('%') != -1 ? this.height : this.height + 'rpx';
  117. }
  118. },
  119. created() {
  120. // 由于一些特殊原因,不能将此变量放到data中定义
  121. this.observer = {};
  122. },
  123. watch: {
  124. isShow(nVal) {
  125. // 如果是不开启过渡效果,直接返回
  126. if (!this.isEffect) return;
  127. this.time = 0;
  128. // 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
  129. this.opacity = 0;
  130. // 延时30ms,否则在浏览器H5,过渡效果无效
  131. setTimeout(() => {
  132. this.time = this.duration;
  133. this.opacity = 1;
  134. }, 30)
  135. }
  136. },
  137. methods: {
  138. // 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
  139. clickImg() {
  140. let whichImg = '';
  141. // 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
  142. if (this.isShow == false) whichImg = 'lazyImg';
  143. // 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
  144. // 当然,也可以给错误的占位图元素绑定点击事件,看你喜欢~
  145. else if (this.isError == true) whichImg = 'errorImg';
  146. // 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
  147. else whichImg = 'realImg';
  148. // 只通知当前图片的index
  149. this.$emit('click', this.index);
  150. },
  151. // 图片加载完成事件,可能是加载占位图时触发,也可能是加载真正的图片完成时触发,通过isShow区分
  152. imgLoaded() {
  153. // 占位图加载完成
  154. if (this.loadStatus == '') {
  155. this.loadStatus = 'lazyed';
  156. }
  157. // 真正的图片加载完成
  158. else if (this.loadStatus == 'lazyed') {
  159. this.loadStatus = 'loaded';
  160. this.$emit('load', this.index);
  161. }
  162. },
  163. // 错误的图片加载完成
  164. errorImgLoaded() {
  165. this.$emit('error', this.index);
  166. },
  167. // 图片加载失败
  168. loadError() {
  169. this.isError = true;
  170. },
  171. disconnectObserver(observerName) {
  172. const observer = this[observerName];
  173. observer && observer.disconnect();
  174. },
  175. },
  176. beforeDestroy() {
  177. // 销毁页面时,可能还没触发某张很底部的懒加载图片,所以把这个事件给去掉
  178. //observer.disconnect();
  179. },
  180. mounted() {
  181. // 此uOnReachBottom事件由mixin.js发出,目的是让页面到底时,保证所有图片都进行加载,做到绝对稳定且可靠
  182. this.$nextTick(() => {
  183. uni.$once('uOnReachBottom', () => {
  184. if (!this.isShow) this.isShow = true;
  185. });
  186. })
  187. // 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
  188. setTimeout(() => {
  189. // 这里是组件内获取布局状态,不能用uni.createIntersectionObserver,而必须用this.createIntersectionObserver
  190. this.disconnectObserver('contentObserver');
  191. const contentObserver = uni.createIntersectionObserver(this);
  192. // 要理解这里怎么计算的,请看这个:
  193. // https://blog.csdn.net/qq_25324335/article/details/83687695
  194. contentObserver.relativeToViewport({
  195. bottom: this.getThreshold,
  196. }).observe('.u-lazy-item-' + this.elIndex, (res) => {
  197. if (res.intersectionRatio > 0) {
  198. // 懒加载状态改变
  199. this.isShow = true;
  200. // 如果图片已经加载,去掉监听,减少性能的消耗
  201. this.disconnectObserver('contentObserver');
  202. }
  203. })
  204. this.contentObserver = contentObserver;
  205. }, 30)
  206. }
  207. }
  208. </script>
  209. <style scoped lang="scss">
  210. @import "../../libs/css/style.components.scss";
  211. .u-wrap {
  212. background-color: #eee;
  213. overflow: hidden;
  214. }
  215. .u-lazy-item {
  216. width: 100%;
  217. // 骗系统开启硬件加速
  218. transform: transition3d(0, 0, 0);
  219. // 防止图片加载“闪一下”
  220. will-change: transform;
  221. display: block;
  222. }
  223. </style>