直接上代码：
参考：http://www.cnblogs.com/zishang91/p/8507485.html

小程序静态页面代码

<scroll-view class="container" scroll-y style="padding-top:0">  
  <view wx:for="{{img}}" class="list-item" wx:key="index"> 
    <image class="list-img" lazy-load src="{{lazyloadArr[index] ? item : '/images/default.png'}}"></image>
    <view>图片{{index}}</view>
  </view>
</scroll-view> 

App.js

//app.js
App({
  onLaunch: function () {
    var _this = this;
    wx.getSystemInfo({
      success: function(res) {
        _this.globalData.windowWidth = res.windowWidth;
        _this.globalData.windowHeight = res.windowHeight;

      },
    })
  },
  globalData: {
    userInfo: null,
    windowWidth: 0,
    windowHeight: 0,
  }
})

JS代码

//index.js
//获取应用实例
const app = getApp()

Page({
  data: {
    img: [
      "https://picsum.photos/500/300?image=100",
      "https://picsum.photos/500/300?image=101",
      "https://picsum.photos/500/300?image=102",
      "https://picsum.photos/500/300?image=103",
      "https://picsum.photos/500/300?image=104",
      "https://picsum.photos/500/300?image=106",
      "https://picsum.photos/500/300?image=107",
      "https://picsum.photos/500/300?image=108",
      "https://picsum.photos/500/300?image=109",
      "https://picsum.photos/500/300?image=110",
      "https://picsum.photos/500/300?image=111",
      "https://picsum.photos/500/300?image=112",
      "https://picsum.photos/500/300?image=113",
      "https://picsum.photos/500/300?image=114",
      "https://picsum.photos/500/300?image=115",
      "https://picsum.photos/500/300?image=116",
      "https://picsum.photos/500/300?image=117",
      "https://picsum.photos/500/300?image=118",
      "https://picsum.photos/500/300?image=119",
      "https://picsum.photos/500/300?image=120",
      "https://picsum.photos/500/300?image=121",
      "https://picsum.photos/500/300?image=122",
      "https://picsum.photos/500/300?image=123",
      "https://picsum.photos/500/300?image=124",
      "https://picsum.photos/500/300?image=126",
      "https://picsum.photos/500/300?image=127",
      "https://picsum.photos/500/300?image=128",
      "https://picsum.photos/500/300?image=129"
    ],
    lazyloadArr: [],
    lazyloadHeightArr: [],
  },
  onLoad: function() {
    let _this = this;
    let _arr = _this.data.lazyloadArr;
    let _imgArr = _this.data.img;
    _imgArr.forEach(function(item,index) {
      _arr.push(false);
    })
    _this.setData({
      lazyloadArr: _arr
    })
  },
  onReady: function () {
    let _this = this;
    setTimeout(function() {
      _this.getRect()
    }, 1000)
  },
  getRect: function() {
    var _this = this;
    wx.createSelectorQuery().select('.list-item').boundingClientRect(function(rect) {
      _this.setData({
        itemHeight: rect.height
      })
      _this.init(rect.height)
    }).exec();
  },
  init: function(itemHeight) {
    let _this = this;
    let _arr =  _this.data.lazyloadArr;
    let _arrHeight = _this.data.lazyloadHeightArr;
    let index = parseInt(app.globalData.windowHeight / itemHeight);
    // 获取未滚动时整屏显示的行数，每行有两个，故 *2 这屏的先加载
    for(let i = 0; i < index * 2; i++) {
      _arr[i] = true
    }

    // 遍历每个图片相对于顶部的高度
    for(let i = 0; i < _arr.length; i++) {
      _arrHeight[i] = Math.floor(i) * (itemHeight + 10)
    }

    _this.setData({
      lazyloadArr: _arr,
      lazyloadHeightArr: _arrHeight
    })
  },

  onPageScroll: function(e) {
    let _this = this;
    let _arrHeight = _this.data.lazyloadHeightArr;
    let _arr = _this.data.lazyloadArr;

    for(let i = 0; i < _arrHeight.length; i++) {
      if(_arrHeight[i] < e.scrollTop + app.globalData.windowHeight) {
        if(_arr[i] === false) {
          _arr[i] = true;
        }
      }
    }

    _this.setData({
      lazyloadArr: _arr
    })

  },
  
})

如果需要翻页的话：
在调用接口返回成功中写入如下代码

let dataList= res.data.data.dataList;
// 懒加载
let _arr = _this.data.lazyloadArr;
let _arrHeight = _this.data.lazyloadHeightArr;

// 懒加载
dataList.forEach(function(item,index) {
  _arr.push(false);
})
let itemHeight = _this.data.itemHeight;
// 遍历每个图片相对于顶部的高度
for(let i = 0; i < _arr.length; i++) {
  _arrHeight[i] = Math.floor(i) * (itemHeight + dataList.length)
}

_this.setData({
  list: dataList,
  lazyloadArr: _arr, // 懒加载数组
  lazyloadHeightArr: _arrHeight, // 懒加载高度数组
})