this is my first question so any suggestions on how to write better Questions on stackoverflow will also be appreciated!
Ok, so I have a UICollectionView with a bunch of cells, and let's say that on a device, the user touches the first cell and then glides over the other cells without lifting her finger. I'm trying to figure out how to call a function (that is specific to every cell) whenever the user's finger slides out of the current cell and into the area of another. From what I understand, I think it's like the TouchDragEnter event for UIButtons (maybe).
Right now, if a user drags her finger over the cells it simply fires the function associated to the first cell she touched, but none of the others. Please help and thanks in advance!
Controls, such as UIButton, respond to touch drag events only if the event starts in that control. From Apple's docs for touchDragEnter:
This event is delivered only if the touch originated inside the control's bounds, exited the bounds, and then entered the bounds again.
If you want to detect dragging from outside to inside of an object, you probably want to use touchesBegan / touchesMoved / touchesEnded or UIPanGestureRecognizer in the superview.
Here's a bit of example code that you may find useful: https://stackoverflow.com/a/52010135/6257435
Related
I'm rather confident [editable] UITextView's become firstResponder when a long press or tap gesture occurs within the scrollView. I want to identify where in the view this touch occured. Digging through the documentation and source code didn't yield me much. I might be going about this wrong. My concern is a race condition if I just add my own tap recognizer (how can I be sure it is called before the textView's delegate methods).
For practical clarification, I want to call two similar functions from a delegate function (editingDidBegin) but depending if they touched the left or right half of the text view, I want to call either of the two.
I'm having a bit of of a pain point in figuring something out.
I have a uitableviewcontroller, and each cell is static. Inside each cell is a textbox. When the user TAPS on a textbox, I'd like an event to fire.
So while I'd like my table to still scroll, i'd also like tap events to work when you tape the textbox.
Apparently in uitableviews, they add a delay to your tap so you have to hold your finger down for a second or so for 'tap' to register. I felt this was not intuitive to a user, so I did this to fix it:
for subview in self.tableView.subviews as [UIView]
{
if subview is UIScrollView
{
let scroll = subview as UIScrollView
scroll.delaysContentTouches = false
break
}
}
This works perfectly, and now when I tap my textbox, it instantly executes my tap event! The problem now, however, is some of my textboxes are positioned right where a user would naturally scroll. When they put their finger down (touch down event) to scroll, it's unfortunately being intercepted by the tap event, and prevents scrolling and instead executes my event.
What i'd really want is if the user puts their finger down, and then swipes, it doesn't execute the touch down event. I thought to be clever and switch touch down to touch up, but when I put my finger down and then pick it back up, it does nothing (touch up inside seems to do nothing). I read this was because it only works on buttons and things like that, and not textfields. So, yes, now I can scroll without my action, but when I tap the textbox and lift my finger up it doesn't execute that, either.
Any ideas on how to either
1) permit touch downs and scrolling to co-exist without having to hold my finger down for a second and deal with that delayContentTouches?
2) somehow get a tap up inside event to fire when I tap on a textbox?
I saw some info here but didn't seem to help much:
UIButton inside UITableViewCell steals touch from UITableView
Thanks!
Well, as luck would have it, I was able to figure this out. Would love some criticism/advice if something might not be ideal here, but what I did was add this to my subclassed textfield:
override func canBecomeFirstResponder() -> Bool {
performMyFunctionHere()
return false
}
So I am returning false on first responder which prevents any sort of keyboard appearing (which is what I wanted) and instead using performMyFunctionHere() I can do what I wanted to do (in my case, make an action sheet picker appear). I assign the action sheet picker in my view controller and assign it to each specific instance of my subclassed uitextfield. Nothing really complicated, to be honest. I'm surprised this works as well as it does.
By the way one thing that didn't seem extremely important was setting the delaysContentTouches as I mentioned above. I guess because now it's using the responder it will always work? It didn't seem to matter whether I removed it or not, but would love thoughts on whether it's better to leave it in or not.
Thanks!
I'm working on an app where the user is expected to rapidly touch and swipe across multiple UIViews, each of which is supposed to do an action once the user's finger has reached it. I've got a lot of views and so the typical thing to do, where I'd iterate over each view to see if a touch is inside of its bounds, is a no-go - there's just too much lag. Is there any other way to get touch events from one view to another (that is beside the first one)? I thought maybe there is some way to cancel the touch event, but I've searched and so far have come up empty.
One of the big problems I have is that if I implement my touch handling in my view controller, touchesBegan only fires for the first touch - if the user touches something and then, without moving the first finger, taps on something else, that tap is not recorded in either touchesBegan or touchesMoved. But if I implement my touch handling in the UIViews themselves, once a view registers a touch, if the user does not lift their finger up and moves it, the views around the first view do not register the touch. Only if the user lifts his finger and then puts it back down will the surrounding views register the touch.
So my question is, lets say I have two views side by side, my touch handling code is implemented in the views, and I put my finger down on view 1. I then slide my finger over to view 2 - what do I need to do to make view 2 register that touch, which started in view 1 and never "ended"?
Set userInteractionEnabled property of UIView to NO.
view.userInteractionEnabled = NO;
UIView has the following property:
#property(nonatomic, getter=isUserInteractionEnabled) BOOL userInteractionEnabled
Ok, I figured out what was going on. Thing is, I have my views as subviews of a scrollview, which is itself a subview of my main view. With scrollEnabled = NO, I could touch my subviews - but apparently the scrollview was only forwarding me the initial touch event, and all subsequent touches were part of that initial event. Because of that, I had many weird problems such as touching two views one after the other, both would select and highlight, but if I took the first finger off the screen both views would de-select. This was not the desired behavior.
So what I did is I subclassed the scrollview and overrode the touch handling methods to send the events to its first responder, which is its superview, which is the view where I'm doing my touch handling. Now it works!
I know this has been probably asked before but I've seen many approaches and i don't know which is best for me, so plz don't send me a link to another post unless it addresses my problem directly.
I have a controller which has a uiview on the top (like a header) (this header is bigger than it seems because is partially hidden on top). on that view i have a uibutton which now with a touch up inside shows the entire header view and taping again returns it to its starting position (changing frame with animation). I want to also be able to drag the view but only changing position on the y axis(dragging up and down)... i was thinking of adding the dragInside/Outside event to the button but this doesn't give me the position of the finger... and also want to know when the user releases the drag so the view ends animation to any of its two possible states (showing or partially hidden). Is this a "touches began" , "touches moved" , "touches ended" thing? if it is please provide a code example. I also want to do this with another view but this is on the left side... same thing but this one moves on the X axis... any help is appreciated. or maybe it can be made with drag event if i only can save a CGpoint of last touch, maybe that's better, any other suggestions
Look at using a UIPanGestureRecognizer to detect the touch movements. Use the translationInView: of the gesture to set the view y position. The translation is the total movement since the start of the gesture so you don't need to remember and accumulate the offset position yourself.
The main thing to worry about while implementing this is bounding the y position of the view so that no matter how far the user drags the view won't go too high or low on the screen.
Use a UIPanGestureRecognizer, that's a class dedicated to handling such drag/pan gestures.
Everything is described here in Apple's documentation, including examples, so you should find your answer here.
There is also some sample code in Apple Developer Library that shows you how to use Gesture Recognizers if needed.
I have a situation where I apply an effect to a UIView when a touch begins and reverse that effect when that touch ends. So basically I am tracking touchesbegan, touchesEnded and touchesCancelled methods of UIView.
But the problem is that when the view goes out of the screen, i.e. when it or one of its parents gets removed from superview, it does not get any more touch events. Is there any way to give this "last" touchesended event to the view? Maybe if the UIView gets notified about being invisible, I can also use this event for that purpose.
Ok I am going to move the answers in comments to original question to make a good summary of important points.
The reason I am tracking touch events is that I want to apply some
nice effects such as glowing on touch start and remove those effects
on touch ending.
The reason why I can not simulate touchesEnded on removing those
views is that I do not directly remove them. Instead I remove one of
the ancestor views of them. I can not keep track of ancestor views
all the way to UIWindow, it is technically impossible I think.
Instead, framework should provide this to as an event I think.
I solved my problem by overriding -(void)willMoveToWindow:(UIWindow *)newWindow method and checking if newWindow is nil.