I wrote a custom pinch gesture recognizer for my ScrollView's zooming, and I handle pinch touches in a method in my view controller.
But in some cases, I want the ScrollView to behave exactly as it would normally behave (if it used the standard pinch gesture recognizer that comes with ScrollView).
Is there some way that in such cases I can pass my custom gesture recognizer to the ScrollView and it would use that recognizer to scale the view as it normally would?
Could I pass the gesture recognizer to the selector that is triggered by pinch actions?
I have not tried this, but here's an idea:
When you set your own gestureRecognizer, store the ScrollView's pinchGestureRecognizer in an iVar. You should then be able to dynamically exchange your gestureRecognizer and the original one.
As of iOS 5 UIScrollView exposes a pinchGestureRecognizer property, but this is read-only. To get it to use your own instead you have to subclass UIScrollView and overwrite this property hoping that internally UIScrollView also uses this property to get the gesture recognizer to add when zooming is enabled.
However it is quite dangerous messing with scroll view's gesture recognizers, especially to modify their behavior. Even just having a different delegate will trigger an exception. So proceed at your own risk.
Related
I am interested in getting the touch location (e.g. something that is, or mimics touchesMoved) in a view controller's view while still keeping a UIScrollView subview enabled. Since all of the touchesDidSomething methods are consumed by the UIScrollView, my hope is that there's a roundabout way of achieving this.
Here are a few things I've tried:
Subclassing a UIScrollView, overriding it's touchesMoved method and passing that touch information to a custom delegate method in my scrollView's view controller. --> This actually works if I deselect "cancellable content touches" and "delays content touches" on my scroll view but it prevents my scroll view from scrolling.
Using the same tactic as above but with a subclassed UIView as a sibling to my UIScrollView. Hence, the hierarchy is as follows:
view
UIScrollView
Subview
Subview
CustomUIView <-- custom UIView that calls delegate
Both of these methods work to the extent that I can grab the data, but at the expense of my scroll view not scrolling anymore. I know I can grab the location of a touch event in a UIScrollView similar to a touchesBegan while the scrollView continues to work but I haven't found a way to get continuous touch events while scrolling. Is this possible?
Here's an illustration of what I'm after:
For some metadata as to why I'm looking for this and why grabbing something like scrollViewDidScroll's contentOffset.x won't work, I'm specifically interested in when the scrollView has scrolled to the end (or beginning) and a user is attempting to keep swiping forward (or backward) even though the scrollView can't scroll in the swiped direction anymore. When this happens I want to detect the forward (or backward) swipe motion to initiate a slick transition to another view.
I solved this by adding a panning gesture recognizer to my view and using it's translationInView method (UISwipeGestureRecognizer doesn't have this method). Example below
let panGesture = UIPanGestureRecognizer(target: self, action: #selector(myMethod(_:)))
panGesture.delegate = self
self.addGestureRecognizer(panGesture)
func myMethod(sender: UIPanGestureRecognizer) {
// sender.translationInView(self).x
}
Also making sure to return true for shouldRecognizeSimultaneouslyWithGestureRecognizer in the UIGestureRegognizerDelegate to account for the scrollView.
I want to make a custom UITextView that functions exactly like the standard text view but extends just a UIView without any gesture recognizers . Since a UIScrollView is basically a UIView with added gesture recognizers I figured this is just a matter of overriding the method of UITextView, inherited from UIScrollView, in which the view has gesture recognizers added to it. Does anyone know which methods these are so my custom text view can skip adding a pan and pinch gesture recognizer altogether? Right now, I have my custom textview remove all of its gesture recognizers upon initialization which seems icky on the performance end.
I have a scrollView and it contains a subView. SubView has a panGesture added to it.
What I want:
I need pangesture to work on subview only if the panning is done vertically. If the panning happens horizontally, I want the scrollView to respond for the panning instead of subview. How can I acheive this
Note: Iam able to find programatically when the panning happens horizontally.
There are several ways to do this:
Depending on what your subview does, you maybe able to replace it with a scrollview and lock it to scroll only vertically. (while the super should scroll only horizontally).
You can try feeding the touch information from the subview to it's superview if the pan gesture is moving horizontally. You could do this using a delegate pattern or, if you know what you're superview is, just access superview in your subview. However, this creates a strong coupling between the two views and probably shouldn't be done. It would be fragile and many would consider it code smell.
(best option) - Subclass UIGestureRecognizer and create your own gesture recognizer that only recognizes vertical movement. Use that instead of the UIPanGestureRecognizer.
Option 3 is the best, but probably the most work. You'll want to read Apple's docs on subclassing UIGestureRecognizer: Apple Docs - UIGestureRecognizer.
I've also written my own drag gesture recognizer, FlxDragGestureRecognizer.m, FlxDragGestureRecognizer.h (similar to a pan gesture recognizer), which you can use if you'd like, or take a look at to get a good idea of how to subclass UIGestureRecognizer. You can use this class to recognize touches moving only in certain directions, otherwise it will fail (which will allow other gesture recognizer to recognizer, like the scrollview). It also has a lot of other customizations and information it gathers, like velocity.
Since you already know how to detect the panning, then in you will need to implement a delegate protocol in your superview, a delegate property in your subview and assign your superview as a delegate for your subview.
when detecting horizontal panning, call the delegate method, when detecting vertical panning, implement what you want in the subview.
I have a uiscroll that allows pinching, panning and single/doubletap functionality. I would like to add a three finger pinch in/out to trigger something else in my app. Pinch in and do this, pinch out and do that.
The builtin scroll pinch allows 2 fingers by default. How would I add a third? Subclass? Do I have to remove the gestures already on the scrollview?
Create your own custom subclass gesture to handle the three pinch gesture. Act as it's delegate so you can instruct it to be active at the same time as other gestures. Require it to only start when there are 3 touches. You don't need to remove / replace the standard gestures on the scroll view.
I was originally using the UITouch methods (touchesMoved: withEvent:) in order to detect the movement in a view. Due to the fact that it seemed not to update often enough I switched to using a UIPanGestureRecognizer (though this didn't actually fix the initial problem).
After using this the touches received for movements responded no matter what it was touching (different subviews) which I actually prefer. However now I have an issue with all the subviews which have movement. I need the gesture recognizer to still move the view even while touching subviews, however if the subview also moves in this direction (left/right) I need my recognizer to cancel.
It seems like gestureRecognizerShouldBegin: might be somewhere to start, but in my case, I cannot account for all subviews.
Is it possible to make pan gesture recognizer cancel if the subview (i.e. another pan recognizer, UISlider, horizontal scrollview, etc.) touched needs to be moved in left/right directions without having to account for each subview individually?