I'm making a drawing app and I would like it to accept pictures that are bigger than the screen. For this, I put an image view in a scroll view. However, when the drawing tool is enabled I want to disable the detection of touch events on the scroll view so that I can use the touchesBegan, touchesMoved and touchesEnded methods for drawing. It seems that even if the scroll view has scroll disabled, these methods are not getting called. How can I go about doing this?
Try turning userInteractionEnabled to NO. Maybe it helps.. :)
Related
My ImageView rotates but while it rotates it doesn't recognize touches on itself.
Do you think it's okay if I create a button via code that's over the ImageView that recognizes the touch?
When an animation is applied on any UIView or any subclass object of a UIView like UIImageView, UIButton etc then it does not detect touch events because when an animation is applied to a view, the animated property changes to its end value right away. what you are actually seeing on screen is the presentation layer of your views layer.
To answer your question, Yes, you can make a UIButton that covers up the area of the UIImageView to detect touch events on it. That sounds like the easiest to implement option in this case.
Apart from that, this link may also help you in the process. Hit testing animating layers
I have been trying to create a scrollable view using UIScrollView. I want this view to be a scratchpad where I can do rough work with touch gestures.
But, doing a drag gesture makes the UIScrollView move the page.
This is why I want to disable scrolling on gesture and enable scrolling only when I drag the scroll bars on the screen.
I have tried Googling, but haven't found any result so far.
It would be great if you could guide me to a solution or help me with some pointers.
Not sure you can or that it would be usable.
How about enabling scrolling only with 2 fingers? By setting the scroll view pan gesture minimumNumberOfTouches To 2.
Otherwise, think about acting as the delegate of the scroll view pan gesture, specifically for gestureRecognizer:shouldReceiveTouch: so that you can examine the touch position and only allow the gesture to start of significantly close to the edge of the view.
I world recommend using this library: https://github.com/BasheerSience/BRScrollBar
1- Use instance method to add the scrollBar
2- in your UIViewController add these lines of code
// First intit by using the instance method
_brScrollBarController = [BRScrollBarController initForScrollView:self.scrollView
inPosition:kIntBRScrollBarPositionRight
delegate:self];
// show the scrollBar always, do not hide
_brScrollBarController.scrollBar.hideScrollBar = NO;
// disable scrolling for your scrollView
self.scrollView.scrollEnabled = NO;
3- now your scrollView will not respond to gestures, and you will use BRScrollView to scroll by dragging the bar
let me know if you have any questions
Think of a UIScrollView with embedded (subview) UIViews, arranged in a column. In iOS6 and previously, the scroll view could be configured so that when you flick it with your finger, the embedded views do not receive touch events even if the initial touch is on one of the subviews; but if you touch a subview without flicking, the scroll view decides this is not a scroll action and forwards the touch events to the embedded views. This was very convenient behavior if you wanted to be able to drag/drop the embedded UIViews within the UIScrollView.
In iOS 7 the documentation indicates that setting the UIScrollView property delaysContentTouches will cause touch-down events to be delayed until the UIScrollView decides whether it's being scrolled. But in fact, this simply does not appear to work. The subview immediately receives touch events and responds to them if the scrolling touch-down event is on one of the subviews. Thus if the subview is programmed for drag/drop it starts dragging while the scroll view also scrolls.
It appears that the model for this behavior has been changed, since iOS 5/6 both did suppress touch events while deciding whether this is a scroll action. Some new methods are now available to cancel the touch-down events after the UIScrollView decides it is scrolling. But obviously this is not useful if the drag/drop code has also started moving the subview.
My question: Is there any way to prevent iOS 7 UIScrollViews from invoking low-level touch-down events on its subviews, when you initiate a scrolling action by stroking a subview?
When I say "low-level", I mean actual touch events as opposed to using gesture recognizers. I am convinced that simply setting the delaysContentTouches property to YES does not work.
This problem has totally busted some quite complex code that worked smoothly and beautifully in iOS 5 and 6; and, so far I have discovered no way to tell the UIScrollView to suppress events to its subviews until it determines whether or not it is being scrolled. The events go through, then a cancellation touch event is triggered later, after the scroll view determines it is scrolling. It looks like the underlying model has been redefined for the worse, or this is a bug. Any insights will be greatly appreciated.
Are you sure it was working on iOS5/6? Based on my experience and posts like UIScrollview delaysContentTouches issue it doesn't work.
Maybe a sample code which shows it working on iOS5/6 but not on iOS7 will help to answer your question.
This works for me:
[scrollView setCanCancelContentTouches:YES];
[scrollView setDelaysContentTouches:YES];
I have been looking to all the other similar topics here, using UIGestureRecognizers, using hitTest:withEvent, pointInside:withEvent: etc. but nothing seems to be ok for what I need to achieve.
Basically I have a main view (self.view of a common UIViewController) and a small rectangular UIScrollView attached onto it at the bottom: the scrollView is filled with some UIImageViews and the user can scroll it as usual.
But the user should also be able to drag one UIImageView (or a copy of it) from the UIScrollView to the main view, and, this is what I am finding really difficult, with the SAME dragging gesture, hence I need a way to:
1) Distinguish between normal horizontal scrolling gesture, which should be handled by the UIScrollView the usual way and a dragging gesture over the image view.
2) Once identified a dragging gesture, should propagate the touch to the superview, which will host a copy of the UIImageView and WITH the SAME dragging gesture continue the dragging over the main view even out of the bounds of the UIScrollView.
Please note that I know that if the UIScrollView has userInteractionEnabled = NO the touch is propagated to the subviews, but 1) I want to propagate it to the superview not the subviews, 2) the userInteractionEnabled property apparently becomes active only once the initial gesture is terminated, while I need to use a single dragging gesture.
Thank you very much for any help.
So, so far I have ended up implementing the touchesShouldBegin:withEvent:inContentView: method of my UIScrollView subclass but with delayContentTouches set to YES (default) instead of NO as #nhahtdh was suggesting.
Strangely enough even only implementing the method was sufficient for my subviews to intercept the dragging, and still my scrollview is scrolling properly, while with delayContentTouches set to NO I was not able to scroll it as all the subviews were starting to move around.
Really the credit for this is #nhahtdh, so man, if you post an answer I will accept it, thank you very much for your help.
I have two views that flip based on a button press within the view. The view has two CAGradientLayers as sublayers. If I flip immediately after the action method fires, the button is in the process of changing the opacity of the gradients and so you see stuttering (the UIVIew flip animation is having to accommodate the button that is itself changing.)
I can hack a solution by doing a performWithSelection:withObject:afterDelay:0.1f, but it feels like such a hack. I tried setting the layer's needsDisplay property and testing for when it was clears, but probably this is insufficient to tell me the screen itself has redrawn.
Dav
In the end this has no solution. I have since found that when animating a view there are severe performance implication if you also try to animate the super views. You can see this in many iOS apps where the app animates an image in a scrolling list - the scrolling stumbles.
So what I learned is either animate something, or it's view, but not both!