I have one UIScrollView inside another UIScrollView, both scrolling vertically. I’m having an issue where when I try to scroll the inner scroll view, the touches are also picked up just afterwards by the outer scroll view. I need touches in the inner scroll view to be exclusively handled by it, and for scrollViewDidScroll to NOT be called on the parent scroll view.
I’ve tried all manner of things, subclassing the scroll view and overriding hitTest:withEvent, setting canCancelContentTouches, setting exclusiveTouch, nothing work at all. The scrollViewDidScroll methods are fired first on the inner one, then on the outer one.
How can I effectively kill the touch after the first scroll view, and not pass it up the responder chain to the outer scroll view?
(FYI: The hierarchy is that there’s a child view controller inbetween, so the outer scroll view contains a child view controller, which in turn contains the inner scroll view).
Apple definitely DOES NOT discourage UIScrollView inside UIScrollView. It's actually in the doc:
your application does not need to do anything to support nesting scrolling. It is supported and provided by default.
https://developer.apple.com/library/content/documentation/WindowsViews/Conceptual/UIScrollView_pg/NestedScrollViews/NestedScrollViews.html
If you want to disable the parent scroll view from scrolling, you can probably send a notification from the child, and set isScrollEnabled in parent.
Related
I have a vertically-scrolling scroll view that has a single subview. This subview has a couple of collection views. I want them to scroll horizontally. It doesn't work because they are inside the scroll view.
The problem is that the pan/scrolling gesture is working just for the scroll view and it doesn't propagate to the collection views. I just see the scroll view scrolling.
There is the same problem with tapping on a collection cell. This event just doesn't happen.
I already tried adding the gestures manually but I am not able to scroll the collection views.
How can I propagate all the gestures ?
Thank you !
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Suppose there are two UIVIew subclasses in two different regions of the screen.
The first UIView subclass is a table or collectionView
The second view is a simple UIView.
Is it possible for gestures inside the second view to be "carried over" to the first view so that for example, a swipe up gesture in the second view would make the table/collection view scroll up ?
In WWDC 2012 Session 223: Enhancing User Experience with Scroll Views, Apple engineers explained that you can take a scroll view's panGestureRecognizer and add it to a different view to make that other view control the scroll view's scrolling.
Note that UITableView and UICollectionView are subclasses of UIScrollView.
So if you can put your table view and your second view into a common superview, you can move the table view's panGestureRecognizer to the superview and it will detect touches on both subviews.
[commonSuperview addGestureRecognizer:tableView.panGestureRecognizer];
The best way to achieve that is to encapsulate your 2 views in a another view and to add the GestureRecognizer on the motherView.
This way when the gesture triggers, with the location of the touch you can figure out if it started in one view or the other and you can track the move all the way to the second view.
I've got a UITableView and a big "button" view in front of it. The "button" view, which has transparent areas, should be able to response to a tap. But enabling user interaction for this view blocks any scrolling touches from getting to the table view located under the "button" view.
The upper view is a UIView (not UIButton). Given how the two views work together, the upper view is essentially part of what's going on with the table view and reacts to the table view being scrolled. But scrolling is the main thing and I'd like the user to have the largest scrolling area possible.
How do I best resolve this conflict so that the table view is scrollable as usual?
I guess you could subclass your UIButton and UITableView common superview, and override its hitTest:withEvent: to verify which view is hit, something like if you are in a clear or an opaque part of the button?
As pbush25 is mentionning however, it goes more or less against Apple's recommendation.
My collection view controller is not responding when swiping on a cell(touch begin in a point on the cell). But it interacts when swipe began a point such as spaces between the cells.
It was previously scrolling vertically, not touch gestures(there was once but i deleted it and nothing really changed) and recognizers in collection view and cell. The interesting part is collection view's didSelectCellAtRow works perfectly fine when interact on cell but not responsive to scrolls.
You can only scroll when swiping from the spaces between the cells or any point in collection view that is not containing cell.
Any thoughts?
Are you sure the touch-down event is passed to the table view (scroll view) correctly?
Make sure the cells don't have a custom touch-down event (e.g. tap gesture recognizer, or touchesBegan method without calling the super inside) and also make sure the collection view delays content touches, it's a common mistake to uncheck it and forget it, and then try to understand why a view is not handling touches properly, but its children are.
I'm building an iOS layout which consists of a UITableView and a UIScrollView. The UIScrollView is inside a table cell of the UITableView and can be scrolled both horizontally and vertically. The diagram below shows this situation. If the user begins scrolling down/up on the UIScrollView the scrolling event should trigger setContentOffset of the table view, and not setContentOffset for the scroll view while the top of the scroll view will be on the dotted line (it's constant height). Then a scrolling touch event should trigger setContentOffset for the scroll view, not for the table view.
In another case: When the user starts scrolling on the table view, it should trigger setContentOffset for the table view, until the scroll view reaches the dotted line. Then the scroll view should handle setContentOffset.
My problem is how to transfer touch events between the table view and the scroll view during one sliding action.
This sounds like one of those cases where you want something quite specific and custom. So trying to do something clever with the gesture recognizers won't be enough.
The main problem is that the ways you can control gesture recognizers such as with gestureRecognizer:shouldReceiveTouch: and gestureRecognizerShouldBegin: only affect the start of the gesture (or for new touches, not ongoing ones), but you want a single ongoing gesture to transition between controlling each view. So for this reason I think you will need to place a large transparent view over your entire screen with a pan gesture recognizer on it and in your handlePan method decide which view you want to adjust and then call setContentOffset directly on that view. You can use the translation of the pan recognizer and the existing content offset to calculate the new one. I know this isn't very elegant, but I can't think of another way to achieve the effect you want.
I'm not sure if this is going to work, but you could try doing something like this:
Option
self.scrollView.panGestureRecognizer = self.tableView.panGestureRecognizer;
Option
[self.scrollView addGestureRecognizer:self.tableView.panGestureRecognizer];
Option
[self.tableView.panGestureRecognizer requireGestureRecognizerToFail:self.scrollView.panGestureRecognizer];