uiscrollview仅允许向后滚动

Question

I have a scroll view that I would like to only allow the user to scroll back. They press a button to make a selection and that scrolls forward, this part works.

Answer 1

I assume back/forward refers to up and down. First, I'd save the scroll position any time a valid scroll occurs. So say you want to make it so the user cannot scroll up, only down. Whenever they finish scrolling down, the UIScrollViews scrollViewDidEndDecelerating: method will be called. I would set the delegate for the UIScrollView and implement that method. In that method set the contentOffset of the scrollview to your variable. Next, implement the delegate method scrollViewDidScroll: and check the new offset compared to your stored offset. If the y value of the new offset is greater than (or less than, depending on which way you are limiting the user), then manually set the scrollview's offset to the stored offset.