now we are implementing a function, that is, when the page scrolls at a certain height, let the tab bar be positioned to the top. Android can now obtain the height of the scroll bar in real time, but not on Apple. Now, the height can only be calculated in real time when the page is scrolled or not. When the hand leaves, the height is not calculated, and the height is calculated only when the page scrolls to a stop. There is a boss who knows how the iPhone can be calculated in real time and urgently asks for