uni-app计算scroll-view高度

<view :style="{height: scrollHeight}">
    <view class="swiper-item">
        <scroll-view scroll-y style="height: 100%;  100%;" lower-threshold="50">　　　　　　
            <view class="card">内容...</view>
        </scroll-view>
    </view>
</view>     

　　　

onReady() {
    // 计算scroll-view高度
    uni.getSystemInfo({
      success: resu => {
        const query = uni.createSelectorQuery()
        query.select('.swiper-item').boundingClientRect()
        query.exec(res => {
          this.scrollHeight = resu.windowHeight - res[0].top + 'px';
          console.log('打印页面的剩余高度', this.scrollHeight);
        })
      }
    })
 },