I have a UICollectionView which has UICollectionViewCells inside it. When a user touches the UICollectionView I want to be notified of this until they release their finger. I tried subclassing the UICollectionView like this:
final class MyCollectionView: UICollectionView {
var hasTouch = false
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesBegan(touches, with: event)
hasTouch = true
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesCancelled(touches, with: event)
hasTouch = false
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesEnded(touches, with: event)
hasTouch = false
}
}
But this doesn't work when there are cells in the way because they don't pass their touches on to the collection view. One way of solving this is to set userInteractionEnabled to false on the cells, but I can't do that because I do need userInteractionEnabled to be true on the cells. How can I solve this?
Redesign the interaction. You're trying to do two incompatible things with the collectionview, and swimming uphill against UIKit that way will only lead to tears. It also goes against the expectations of your users, who have seen a lot of collectionviews and expect them to act a certain way.
If you really insist on doing this, what you could do is:
set userInteractionEnabled to false on the cells.
on touch down, check to see if you touched down on a cell, using indexPathForItemAtPoint: (the point is where the touch was)
on touch up, use indexPathforItemAtPoint to see if you are in the same cell. Then, you could manually deal with "selecting a cell"
Then do whatever other stuff you are doing with the touches as well.
Basically, turn userInteractionEnabled off, and handle cell selection yourself.
Related
I'm trying to implement 3D touch on a UITableView. The following code inside a subclassed UITableView works:
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
let touch = touches.first!
if touch.force <= (touch.maximumPossibleForce / 2) {
super.touchesBegan(touches, with: event)
}
else {
print("force touch called !!!")
}
}
However, how I know what particular row within the table is force-touched?
The touch.view is identified as a "UITableViewCellContentView" object while debugging, but this class does not exist in the UIKit. Casting it causes a "Could not cast value of type 'UITableViewCellContentView' (0x107cbab80) to 'UITableViewCell' (0x107cbab30)." runtime error.
How to find out which particular row in a UITableView received a force-touch event? I'm using Swift 4.2 and iOS 12.1.
Thanks!
The content view is a view inside the cell, you can't simply cast it to a UITableViewCell as it is an unrelated type.
You can use indexPathForRow(at:) to convert a CGPoint into an IndexPath. You will need to convert the touch point in the table view's coordinate system, rather than the content view.
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
let touch = touches.first!
if touch.force <= (touch.maximumPossibleForce / 2) {
super.touchesBegan(touches, with: event)
}
else {
print("force touch called !!!")
let tablePoint = touch.location(in:self)
if let indexPath = self.indexPathForRow(at:tablePoint) {
print("\(indexPath.row) touched")
}
}
}
Depending what you are trying to do, you might find it easier to handle the force touch in your view controller via registerForPreviewing and UIViewControllerPreviewingDelegate
I have a custom UIGestureRecognizer for a two finger gesture that works perfectly except for it being very picky about how simultaneously the fingers have to touch the iOS-device for touchesBegan to be called with 2 touches. touchesBegan is often called with only one Touch even though I am trying to use two fingers.
Is there any way to make recognition for the number of Touches more forgiving in regards to how simultaneously you have to place your fingers on the touch screen?
I've noticed that a two finger tap is recognized even when you place first one finger and then another much later while still holding the first finger down.
Here is the code for my touchesBegan function:
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
if touches.count != 2 {
state = .failed
return
}
// Capture the first touch and store some information about it.
if trackedTouch == nil {
trackedTouch = touches.min { $0.location(in: self.view?.window).x < $1.location(in: self.view?.window).x }
strokePhase = .topSwipeStarted
topSwipeStartPoint = (trackedTouch?.location(in: view?.window))!
// Ignore the other touch that had a larger x-value
for touch in touches {
if touch != trackedTouch {
ignore(touch, for: event)
}
}
}
}
For two-finger gestures, touchesBegan is most likely going to be called twice: once you put the first finger on the screen, and once for the second one.
In the state you keep, you should keep track of both touches (or for that matter, all current touches), and only start the gesture once both touches have been received and the gesture's start condition has been met.
public class TwoFingerGestureRecognizer: UIGestureRecognizer {
private var trackedTouches: Set<UITouch> = []
public override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
for touch in touches {
if self.trackedTouches.count < 2 {
self.trackedTouches.insert(touch)
}
else {
self.ignore(touch, for: event)
}
}
if self.trackedTouches.count == 2 {
// put your current logic here
}
}
public override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
}
public override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent) {
self.trackedTouches.subtract(touches)
}
public override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent) {
self.trackedTouches.subtract(touches)
}
public override func reset() {
super.reset()
self.trackedTouches = []
}
}
don't worry about touchesBegan:withEvent: instead use touchesEnded:withEvent: or touchesMoved:withEvent: if the end state does not contain both fingers, set it as .failed otherwise set it as .ended
tapping the screen with more than one finger simultaneously is impossible, so during touchesMoved:withEvent: you will find two fingers. I'm not sure about touchesEnded:withEvent: this one probably won't work since removing two fingers simultaneously is just as hard as applying two fingers simultaneously, but it's worth a try to see how it reacts.
I'd recommend making your code a little more forgiving. Although touchesBegan/Moved/Ended/Cancelled respond to events of "one or more touches" (as stated in the Apple docs) relying on the precision of a user to simultaneously touch the screen with 2 fingers is not ideal. This is assuming you have multi-touch enabled, which it sounds like you do.
Try tracking the touches yourself and executing your logic when you're collection of touches reaches 2. Obviously you'll also have to track when your touch amount becomes more or less and handle things accordingly, but I'd guess you're already handling this if you're gesture is meant to be for 2 fingers only (aside from the extra logic you'd have to add in touchesBegan).
Not sure why the other guys answering with using touchesMoved:withEvent did not answer your question, but maybe you need a github example.
Double touch move example.
Is touchesMoved an option in order for you to achieve the desire outcome? Also you could implement a counter before setting the state to failed
Don't forget to set isMultipleTouchEnabled = true
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
if touches.count != 2 {
print("we do NOT have two touches")
if counter > 100 { // 100 "more fogiven"
state = .failed
}
counter += 1
return
} else {
print("we have to two touches")
}
I am trying to make my interface feel more responsive. A UIView changes color on user touch and I want it to do so already when the View is touched.
I could implement a UITapGestureRecognizer but a tap is not what I am looking for, since it requires the touch to end before being recognized.
I imagine this to be quite simple. Or am I wrong?
Do I create a custom UIGestureRecognizer class?
Have you tried touchedBegan?
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first {
// ...
}
super.touchesBegan(touches, with: event)
}
I'm making a custom keyboard and I'm in a really weird situation.
I've noticed that when I catch the event touchesBegan at the rear left (about 20 pixels) of the UIView (inputView), I'll have some delay in here.
Any action I do in touchesBegan will be perform slower than other area.
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?)
{
self.keypop.hidden = false
}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
{
self.keypop.hidden = true
}
And this trouble affects my app's performance.
In this example, I will not see the keypop appears when I touched on the rear left because self.keypop.hidden was delayed in showing up.
I don't know why, or is this an error from iOS 9?
I've been stuck on this trouble for a week.
In my situation I was using touchBegan in a CollectionView and it was delaying touches when I tap
Its worked with me by simply added this code
In Swift,
self.collectionView.delaysContentTouches = false
/*delaysContentTouches applies to all UIScrollView instances.*/
The answer here seems to have fixed the same issue in our keyboard:
UISystemGateGestureRecognizer and delayed taps near bottom of screen
With the following code:
override func viewDidAppear(animated: Bool) {
let window = view.window!
let gr0 = window.gestureRecognizers![0] as UIGestureRecognizer
let gr1 = window.gestureRecognizers![1] as UIGestureRecognizer
gr0.delaysTouchesBegan = false
gr1.delaysTouchesBegan = false
}
My question: Is there a way to adjust the "sensitivity" of UIPanGestureRecognizer so that it turns on 'sooner', i.e. after moving a fewer number of 'pixels'?
I have a simple app with a UIImageView, and pinch and pan gesture recognizers tied to this so that the user can zoom in and draw on the image by hand. Works fine.
However, I notice the stock UIPanGestureRecognizer doesn't return a value of UIGestureRecognizerState.Changed until the user's gesture has moved about 10 pixels.
Example: Here's a screenshot showing several lines that I've attempted to draw shorter & shorter, and there is a noticeable finite length below which no line gets drawn because the pan gesture recognizer never changes state.
IllustrationOfProgressivelyShorterLines.png
...i.e., to the right of the yellow line, I was still trying to draw, and my touches were being recognized as touchesMoved events, but the UIPanGestureRecognizer wasn't firing its own "Moved" event and thus nothing was getting drawn.
(Note/clarification: That image takes up the entirety of my iPad's screen, so my finger is physically moving more than an inch even in the cases where no state change occurs to the recognizer. It's just that we're 'zoomed in' in terms of the tranformation generated by the pinch gesture recognizer, so a few 'pixels' of the image take up a significant amount of the screen.)
This is not what I want. Any ideas on how to fix it?
Maybe some 'internal' parameter of UIPanGestureRecognizer I could get at if I sub-classed it or some such? I thought I'd try to sub-class the recognizer in a manner such as...
class BetterPanGestureRecognizer: UIPanGestureRecognizer {
var initialTouchLocation: CGPoint!
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent) {
super.touchesBegan(touches, withEvent: event)
initialTouchLocation = touches.first!.locationInView(view)
print("pan: touch begin detected")
print(self.state.hashValue) // this lets me check the state
}
override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent) {
super.touchesMoved(touches, withEvent: event)
print("pan: touch move detected")
print(self.state.hashValue) // this remains at the "began" value until you get beyond about 10 pixels
let some_criterion = (touches.first!.isEqual(something) && event.isEqual(somethingElse))
if (some_criterion) {
self.state = UIGestureRecognizerState.Changed
}
}
}
...but I'm not sure what to use for some_criterion, etc.
Any suggestions?
.
Other alternatives that could work, but that I'd rather not have to do:
I could simply attach my UIPanGestureRecognizer to some parent,
non-zoomed view, and then use affine transforms & such to remap the
points of the pan touches onto the respective parts of the image.
So why am I not doing that? Because the code is written so that
lots of other objects hang off the image view and they all get the
same gesture recognizers and....everything works just great without
my having keep track of anything (e.g. affine transformations), and the problem only shows up if you're really-really zoomed in.
I could abandon UIPanGestureRecognizer, and effectively just write my own using touchesBegan and touchesMoved (which is kind of
what I'm doing), however I like how UIPanGestureRecognizer
differentiates itself from, say, pinch events, in a way that I don't
have to worry about coding up myself.
I could just specify some maximum zoom beyond which the user can't go. This fails to implement what I'm going for, i.e. I want to allow for fine-detail level of manipulation.
Thanks.
[Will choose your answer over mine (i.e., the following) if merited, so I won't 'accept' this answer just yet.]
Got it. The basic idea of the solution is to change the state whenever touches are moved, but use the delegate method regarding simultaneous gesture recognizers so as not to "lock" out any pinch (or rotation) gesture. This will allow for one- and/or multi-fingered panning, as you like, with no 'conflicts'.
This, then, is my code:
class BetterPanGestureRecognizer: UIPanGestureRecognizer, UIGestureRecognizerDelegate {
var initialTouchLocation: CGPoint!
override init(target: AnyObject?, action: Selector) {
super.init(target: target, action: action)
self.delegate = self
}
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent) {
super.touchesBegan(touches, withEvent: event)
initialTouchLocation = touches.first!.locationInView(view)
}
override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent) {
super.touchesMoved(touches, withEvent: event)
if UIGestureRecognizerState.Possible == self.state {
self.state = UIGestureRecognizerState.Changed
}
}
func gestureRecognizer(_: UIGestureRecognizer,
shouldRecognizeSimultaneouslyWithGestureRecognizer:UIGestureRecognizer) -> Bool {
if !(shouldRecognizeSimultaneouslyWithGestureRecognizer is UIPanGestureRecognizer) {
return true
} else {
return false
}
}
}
Generally setting that "shouldRecognizeSimultaneouslyWithGestureRecognizer" delegate to true always is what many people may want. I make the delegate return false if the other recognizer is another Pan, just because I was noticing that without that logic (i.e., and making the delegate return true no matter what), it was "passing through" Pan gestures to underlying views and I didn't want that. You may just want to have it return true no matter what. Cheers.
Swift 5 + small improvement
I had a case when accepted solution conflicted with basic taps on toolbar which also had this betterPanGesture so I added minimum horizontal offset parameter to trigger state changing to .changed
class BetterPanGestureRecognizer: UIPanGestureRecognizer {
private var initialTouchLocation: CGPoint?
private let minHorizontalOffset: CGFloat = 5
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
super.touchesBegan(touches, with: event)
self.initialTouchLocation = touches.first?.location(in: self.view)
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
super.touchesMoved(touches, with: event)
if self.state == .possible,
abs((touches.first?.location(in: self.view).x ?? 0) - (self.initialTouchLocation?.x ?? 0)) >= self.minHorizontalOffset {
self.state = .changed
}
}
}