自定義組件生命周期res.height有的時(shí)候報(bào)null

ready: function () {

var that = this
var query = wx.createSelectorQuery().in(this)
query.select('.question').boundingClientRect(function (res) {
  that.setData({
    questionHeight: res.height
  })
}).exec()
// console.log(that.data.questionHeight)

}