When you're working with an atypical nested UITableViews setup - where you have an outer vertical UITableView that hosts 90° rotated UITableViews (see: Looking for a UI library to present Data horizontaly in iOS ):
is there a way to make iOS process vertical and horizontal touches at the same time?
I found that iOS is very clever in processing touches:
horizontal touches make the relevant horizontal UITableView scroll, while a vertical swipe makes the outer UITableView scroll. Perfect.
Only, I'd love to be able to move my finger diagonally and see the outer UITableView and the inner UITableView scroll at the same time.
I tried a few approaches (playing with canCancelContentTouches, delaysContentTouches, and touch messages) but I haven't found a way to make this happen.
EDIT:
Here's a XCode4 project that shows this behavior: http://marcanton.io/other/stackoverflow/nestedtableviews.zip
EDIT:
I submitted this issue to Apple Developer Technical Support, here's their reply:
Thank you for writing to Apple
Worldwide Developer Technical Support.
I am responding to your inquiry
concerning touch events in embedded
UITableViews.
Typically this is an approach that is
not recommended. The issue is that
UITableView inherits from UIScrollView
and as stated in the documentation for
UIScrollView:
"Important: You should not embed
UIWebView or UITableView objects in
UIScrollView objects. If you do so,
unexpected behavior can result because
touch events for the two objects can
be mixed up and wrongly handled."
http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIScrollView_Class/Reference/UIScrollView.html%23//apple_ref/occ/cl/UIScrollView
So that this time, there is not a
workaround for getting both to scroll
at the same time.
I recommend that you file an
enhancement request at
http://developer.apple.com/bugreporter/
detailing what you would like to see
us add in a future release.
Still, I think that there has to be a way to enable this functionality, although I understand that this is not recommended. In fact, Apple does not even recommend hosting UITableViews inside another UITableView, but with the exception made above, it works quite beautifully.
I'll keep this question updated with our collective findings.
EDIT: There actually is a way, detailed here: http://marcanton.io/blog/nested-orthogonal-tableviews/
This would have to be a custom mirroring of intercepted touch events. Touch events follow the responder chain model, which means that if an object in the responder chain (the top most (outermost) view) cannot handle the event or action, it resends the message to the next responder (in this case the background UITableView in the chain). This is why you are seeing the horizontal events go to the horizontal UITableView and the vertical events going to the vertical UITableView. A diagonal touch event has applicable horizontal and vertical events, so the top-most view (the outer vertical UITableView) can respond to the vertical touches and swallows the event.
If you think about it, all vertical touches likely have a little bit of horizontal events (think about when you flick your finger), so there is likely some work done in the background to determine how to interpret the touch event (either as a vertical or horizontal).
I found this tread on passing events down to the next object in the responder chain. You might want to give this a try as a partial solution to your puzzle. The rest is to figure out how to capture the horizontal touch events and pass them along to the next responder.
Interesting, I haven't played around with this kind of setup yet, but I would try to intercept touch events on the nested UITableViews and delegate any vertical movement to the outer UITableView - and vice-versa.
Related
How can one enable horizontal and vertical scrolling at same time in a grid view?
If I have a 4x4 grid of thumbnail images, I want to implement swiping in both directions, left/right and top/bottom. Currently I am done with left and right swipe, but if I select the second cell and swipe towards the top, the 2nd row should be scrolled like a Rubik's cube.
Please share if any one have any idea.
It's been quite a while since your question but as I've been struggling with the same thing I'm gonna answer it for future reference...
Sadly I could not find a good solution anywhere so after a lot of hours of experimenting I came up with this: https://github.com/AlvinNutbeij/DWGridController
It's still a work in progress but very usable for your purpose I'd say!
How have you currently implemented what you have? Your mention of 'cell' makes it sound like you are using a UITableView. You won't manage to make one of those scroll in both directions, you'll need to work with a UIScrollView.
I suggest you watch "Designing apps with Scroll Views" from WWDC 2010, then "Advanced Scrollview Techniques" from WWDC 2011. That'll teach you about how you implement tiling and infinite scrolling.
Essentially what you want to do is implement some kind of view recycling yourself, that works like the way UITableView recycles its cells. When things are scrolled off one side of the scroll view, you remove the views for the things that just scrolled off screen and put them in a queue. When things scroll onto the screen, you pull views out of the queue (or create new ones if the queue is empty) and lay those views out in the correct place.
To do the infinite scrolling, you fake it: when your scroll view gets near its edge, you reposition everything inside it, you move the scroll view's content offset to where you've repositioned the views, and then you continue from there: it's all done at once so the user never notices.
The videos will explain these techniques better than I can sum up here: watch those as your first point of call.
I'm using a UIScrollView to display a custom UIView. When the user drags a finger across the UIScrollView, there is a noticeable delay before the display begins updating. If the user keeps touching the screen, the UIScrollView becomes very responsive after a short time. Subsequent attempts to scroll result in the same initial delay, followed by high responsiveness. This delay seriously affects the usability of the view and I would like to get rid of it.
In a test project I have written to try to get to the bottom of this issue, I have only been able to partially replicate the behaviour. The first time that the user scrolls is exactly the same - however any subsequent attempts to scroll are responsive straight away.
I have tried both setting delaysContentTouches = NO and subclassing UIScrollView so that touchesShouldBegin returns NO as suggested in multiple places online, but neither has worked.
I'm using MonoTouch on iOS 4.3, but Objective-C answers are fine. I would post code to help illustrate the issue, but since I have been unable to narrow down the problem this would be well over 1000 lines. Hopefully this is enough info to get a solution.
Does anyone know what might be causing this delay, and how I can get rid of it?
Some general suggestions for improving scrolling performance.
Have your scrolling views rasterize offscreen:
myView.layer.shouldRasterize = YES;
Set that property for each sub-view on the scrollview - do not set it for the children of those sub-views or you just eat up memory that way.
If your scrolling views do not need compositing, make sure you turn that blending off:
myView.opaque = YES;
Test using the simulator by leveraging these two features that appear on the Debug menu of the iOS Simulator:
Color Off-screen Rendered
Color Blended Layers
If that doesn't address your problem, and you have implemented UIScrollViewDelegate, double-check to make sure you are not doing anything time consuming in those methods - for example, based on your description, you might be doing something in scrollViewDidScroll, scrollViewWillBeginDragging, or scrollViewWillBeginZooming and if you are, optimize that so it happens before scrolling even begins. Also, make sure you're not doing anything in touchesBegan.
I suspect what is happening is there is some kind of interaction enabled in the content of your scroll view.
The system does not know if the initial touch down is going to be a tap on one of the subviews or a drag on the scroll view, therefore is causing a delay while it waits to see if you are going to lift your finger.
What are the subviews of the UIScroll view?
As an experiment set all the subviews of the UIScrollView to have userInteractionEnabled = NO, this will not be what you want, but its just a test. Is should scroll fine after this, otherwise I am wrong.
I have a UITableView with normal vertical scrolling.
I want to add a UISwipeGestureRecnogiser to it (or somewhere connected in the view hierarchy).
I've done this, but the vertical tolerance on my gesture recogniser is pretty small. So I have to get my horizontal swipe pretty straight, otherwise the UITableView takes over and scrolls vertically. This is pretty annoying for the user.
Has anyone got any suggestions on how to better handle this? Maybe putting a UIView on top of my table view that handles the gesture, but if it fails - somehow pass the event to my table View.....
I ended creating my own gesture recogniser - following the example from the event handling guide for iOS.
I had more control over vertical tolerance using the old touchesMove and touchesBegan.
It still wasn't perfect, but it was a lot better and after testing on a few people, I could see there the swiping was less error prone.
I made a slideview using a uiview and detecting touches to move pages. This slideview is almost like this, except that I made it works like a UITableView.
Now I'm using this to uivews with uiscrollviews. The problem is, "how to distribute touch events to scrollview or slideview?". I had the logic to do. Basically, the uiscrollviews are vertical and slideview is horizontal.
I tried hitTest to keep the touchBegan,Moved,Ended in slideview. When I get a touch movement horizontally, I keep to slideview, when vertically, distribute to uiscrollview. But I cannot figure out how to distribute events to uiscrollview.
Calling [scrollView touchesBegan:touches withEvent:event] doesn't work. I supposed uiscrollview has a different way to work.
If you don't find a clue to your answer, probably, you're wrong.
UIScrollView uses a own way to get touchesBegan, Moved and Ended. Way that I don't, but it's mean if you override touchesBegan to make UIScrollView stops to work, you won't get it. Using hitTest in superview of scroll, you can get the touches before UIScrollView but you can't change the touches target while touches is happening.
After all, there is one way to solve this, ashly, three ways.
1- Simulate touches
I didn't test this, you'll know below. Events come from UIWindow and distributed to subview by - (void)sendEvent:(UIEvent *)event. We don't know how touches target is saved, and change this is completely out of question. But we can use the idea of override superview's hitTest to know what the user will do to make a 'WA' to change the target. To do this, simulate a event of touch ended. Supposed target will be reset. Simulate a event of touch begin again, and this time make sure to let hittest get scrollview.
You can find how simulate events here. The problem is, probably your app will be rejected due using private methods.
2- Make your own UIScrollView
This should be the best or the worst, depending what you want to do. I believe it's painful. And isn't what you want to do right now.
3- Surrender to 'Nest UIScrollView'
To make slideshow of pdf, hq, docs and books, it's the best and painless way. Put a UIScrollView inside another and let them reach an agreement of scrolling. http://developer.apple.com/library/ios/#documentation/WindowsViews/Conceptual/UIScrollView_pg/NestedScrollViews/NestedScrollViews.html
I have a UIWebView which is embedded in a UIScrollView. The webView is resized so that the scroll view manages all the scrolling (I need control over the scrolling).
In the webView I have disabled userSelection via '-webkit-user-select: none;'
Everything is working fine except one annoying detail. When I hold down my finger on the content before starting to scroll for about a second the scrollView won't scroll. My best guess is, that it has something to do with userSelection. The time is about the same it usually takes for the copy/paste/magnifying-thing to appear which usually disables scrolling as well.
I am running out of ideas on how to solve this. Every help would be greatly appreciated!
Thanks!
EDIT: Another aspect of the problem is, that the non-scrolling actually triggers JS-Eventhandler (click, mousedown, mouseup) inside my webView which leads to surprising app behavior. The user puts her finger down, waits, scrolls, nothing happens, removes her finger and this is perceived as a click, which feels wrong from a users perspective.
I would guess what is happening is that after that short duration, the scrollview is no longer interpreting the touch as being on it's view and instead passes the touch down to it's content views.
Have you tried delaying the content touches for the scrollview? This will essentially tell the scrollview to delay taking action on the touch event and instead to briefly monitor the touch and if the touch moves then it recognizes it as a swipe gesture for scrolling. If it doesn't move, it will eventually pass the touch along to it's subviews.
scrollView.delaysContentTouches = YES;
I think even then, there is a standard delay time before the scrollview will pass the touch events along the responder chain. If you hold for too long, it's going to naturally perceive it as being a press down event rather than a scroll event.
This question is not relevant anymore. As of iOS 5.0 the UIWebView is based on a real UIScrollView and also exposes that UIScrollView via a property. Use that instead.
And don't mess with UIWebViews embedded in UIScrollViews anymore. The documentation explicitly advises against that.
Relevant Documentation