function ScrollView({row}) {
  const [isScrollingDown, setIsScrollingDown] = useState(false);
  const [prevRow, setPrevRow] = useState(null);
  if (row !== prevRow) {    // Row changed since last render. Update isScrollingDown.
    setIsScrollingDown(prevRow !== null && row > prevRow);
    setPrevRow(row);
  }
  return `Scrolling down: ${isScrollingDown}`;}