WeChat 미니 프로그램에서 이미지의 지연 로딩 효과 구현

<view class="container">
  <image class="img" src="/images/placeholder.png"/>
  <image class="img" src="/images/placeholder.png"/>
  <image class="img" src="/images/placeholder.png"/>
  ...
</view>

.container {
  display: flex;
  flex-direction: column;
}

.img {
  width: 100%;
  height: 200rpx;
  margin-bottom: 20rpx;
  background-color: #eee;
}

Page({
  data: {
    lazyLoadImgs: [
      "/images/img1.png",
      "/images/img2.png",
      "/images/img3.png",
      ...
    ]
  },
  onReady: function() {
    // 创建IntersectionObserver实例
    this.IntersectionObserver = wx.createIntersectionObserver(this);
    
    // 监听需要懒加载的图片
    this.IntersectionObserver.relativeToViewport().observe('.img', (res) => {
      if (res.intersectionRatio > 0) {
        // 图片进入了可见范围，开始加载图片
        const index = res.dataset.index;
        const lazyLoadImgs = this.data.lazyLoadImgs;
        lazyLoadImgs[index] = res.dataset.src;
        this.setData({
          lazyLoadImgs: lazyLoadImgs
        });
      }
    });
  },
  onUnload: function() {
    // 组件销毁时，停止监听
    this.IntersectionObserver.disconnect();
  }
})

<view class="container">
  <image class="img" src="{{lazyLoadImgs[0]}}"/>
  <image class="img" src="{{lazyLoadImgs[1]}}"/>
  <image class="img" src="{{lazyLoadImgs[2]}}"/>
  ...
</view>