Hello,
I'm trying to scroll horizontally through a set of pages, where pages are
grouped by two (and can be zoomed both together). So far, my view hierarchy is:
• One outter UIScrollView that scrolls horizontally.
• Several inner UIScrollView that contains two pages each, scrolling
horizontally too.
The problem I have is that swiping quickly through pages makes the outter
UIScrollView skip the inner pages : only the first page of the inner SV are
visible, and then the outter UIScrollView skip directly to the next page group.
It seems that as long as the outter SV is moving (or decelerating, anyway), the
inners SV won't have a chance to get the swipe events.
I tried several things so far :
• Use touchesShouldBegin:withEvent:inContentView:: If
delaysContentTouch is disabled, this is called during multiple swipes — however
touchesShouldCancelInContentView: is only called for the first swipe, and it's
probably what would be usefull. So no luck there (I think).
• Disable scrolling on the outter SV (scrollEnabled = NO) when entering
a page group, and re-enable it when the inner SV started to scroll (as then the
inner SV will catch all the swiping events): my best try so far. However it's
hard to detect which page group we're going to land on after several swipes.
Plus it seems that an existing touch is not re-aquired right after
scrollEnabled is re-activated, so I miss a few swipes, and the animation is not
smooth as it should be (the scroll stops flatly on groups ends, then resumes on
next swipe).
(Btw, the problem occurs whether paging is enabled or not: it really lies in
the horizontal swipe handling, not in the paging behavior.)
In the end, my question is: how can I prevent the outter UIScrollView from
getting all swipe events when it's decelerating, and tell it to pass them to
the inners UIScrollViews instead?
Additional questions: How does the magic of nested UIScrollView actually works
? And would overriding 'hitTest:' on one of the ScrollViews be a good idea ?
I arranged a small sample Xcode project that demonstrates the issue and the
possible fixes — it is available here :
http://winosx.com/hosted_files/ZoomScrollTest.zip
Thanks!_______________________________________________
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