计算RecyclerView的item可见百分比

曝光需求：根据用户滑动实时计算item可见的百分比，超过50%则计为有效曝光。
代码如下：

private void calculateItemVisiblePercent() {
    if (mRecyclerView == null || mLayoutManager == null || mAdapter == null) return;
    //获取第一个可见item的位置
    final int firstPosition = mLayoutManager.findFirstVisibleItemPosition();
    //获取最后一个可见item的位置
    final int lastPosition = mLayoutManager.findLastVisibleItemPosition();
    Rect rvRect = new Rect();
    //获取recyclerview可见区域相对屏幕左上角的位置坐标
    mRecyclerView.getGlobalVisibleRect(rvRect);
    for (int position = firstPosition; position <= lastPosition; position++) {
      int visiblePercent;
      //根据position获得对应的view
      View itemView = mLayoutManager.findViewByPosition(position);
      int itemHeight = itemView.getHeight();
      Rect rowRect = new Rect();
      //获取item可见区域相对屏幕左上角的位置坐标
      itemView.getGlobalVisibleRect(rowRect);
      if (rowRect.bottom >= rvRect.bottom) { //item在recyclerview底部且有部分不可见
        int visibleHeightFirst = rvRect.bottom - rowRect.top;
        visiblePercent = (visibleHeightFirst * 100) / itemHeight;
      } else { //item在recyclerview中或顶部
        int visibleHeightFirst = rowRect.bottom - rvRect.top;
        visiblePercent = (visibleHeightFirst * 100) / itemHeight;
      }
      if (visiblePercent > 100) visiblePercent = 100;
    }
  }

参考文章链接：https://stackoverflow.com/questions/39503595/how-to-find-percentage-of-each-visible-item-in-recycleview/49168492#