let _this=this
let height=""
const query = uni.createSelectorQuery()
query.select('#u-dropdown').boundingClientRect()
query.selectViewport().scrollOffset()
query.exec(function(res){
// debugger
res[0].top // #the-id节点的上边界坐标
res[1].scrollTop // 显示区域的竖直滚动位置
// _this.height=res.windowHeight-res[0].top +'px'
// =_this.height
height=uni.getSystemInfoSync().screenHeight
_this.viewHeight=height-res[0].top-res[0].height
_this.contentStyle={
zIndex: -1,
opacity: 0,
height:_this.viewHeight+'px'
}
// console.log('打印高度',_this.viewHeight);
// console.log('打印demo的元素的信息',res);
})
}