滚动视图中的“绝对位置”视图

Question

I don't know if this is possible but maybe someone can help me: My scrollview size is 400*400px and what I want is a column/view inside on the left of the scrollview (40px wide) that always stays visible when the user scrolls horizontally, but moves together with the view when the user scrolls vertically.

here's an example

So the red part should always be visible when there's horizontal scrolling and the yellow part becomes visible on vertical scrolling. Any ideas how this can be done?

Answer 1

Set yourself as the delegate of the scrollview and implement -scrollViewDidScroll: . In this method, check the contentOffset of the scrollView and adjust the position of your "absolutely-positioned" view accordingly.

Note that this method is called for every single frame of the scroll, so try not to do anything particularly expensive here. It may be called 60 times a second.