scrollInit() {
    wx.createSelectorQuery().select('#scroll').boundingClientRect((rect) => {
      this.setData({
        scrollBox: rect
      })
    }).exec()
    wx.createSelectorQuery().select('#bar').boundingClientRect((rect) => {
      this.setData({
        barHt: rect.height
      })
    }).exec()
    
  },
  bindscroll: function(e) {
    console.log(e)
    let scrollBound = this.data.scrollBox
    let scrollHeight = e.detail.scrollHeight
    let scrollTop = e.detail.scrollTop
    //滚动条bar高度根据显示区域占内容区域的比例显示
    let barHt = this.data.barHt
    let barTop = (scrollTop / (scrollHeight - scrollBound.height) * (scrollBound.height - barHt));
    this.setData({
      barTop: barTop
    })
  },