The application I'm building has a full-screen MKMapView, with another UIView subclass placed over it, full-screen as well and completely transparent. I would like for the UIView subclass to handle single touch gestures, such as taps and single finger drags, and ignore anything else. This would allow the MKMapView to be interacted with using other means, especially panning/scrolling with two fingers by disabling 3D functions.
My issue here is that MKMapView does not use the touchesXXX:withEvent: methods for its user interaction. So, I can't detect touch count in those methods on the view and forward to the map. Likewise, the hitTest:withEvent: method can't be used to determine which view handles the touches, because the UIEvent object there returns an empty set of touches.
I've considered letting all touches forward through the view and using a gesture recognizer to handle events, but I really need the single touch/drag on the overlay view to have no effect on the map view.
Is there a way to accomplish this filtering based on the number of touches? Or a way to disable the single touch gestures on the map view?
The solution to this is actually very simple.
Give the map view a parent view that it fills completely
Give the parent view pan and tap gesture recognizers configured to only respond to one finger touches
On the MKMapView, set the scrollEnabled property to NO (the "Allows Scrolling" checkbox in IB)
The gesture recognizers allow you to get the gestures, and setting scrollEnabled to NO prevents the MapView from swallowing the pan gestures.
Sample project here: https://github.com/Linux-cpp-lisp/sample-no-gesture-mapview
Related
I'm trying to pass tap events to the superview but handle longpress events. I've added LongPressGestureRecognizer to the top view but the tap events aren't passed to the superview. I tried multiple approaches:
Overriding hitTest doesn't work since the longpress gesture recognizer handler doesn't get called
isUserInteractionEnabled - same as above
Overriding touchesBegan/Ended and calling them manually on the superview doesn't trigger the tap event
Handing complex tap interactions can be hard, and mixing different approaches can make it much much harder.
Generally, the best way to handle it is to have a single view that has multiple gesture recognisers on them. Implement the UIGestureRecognizerDelegate method gestureRecognizer(_:shouldRecognizeSimultaneouslyWith:) and gestureRecognizer(_:shouldRequireFailureOf:) to handle conflicts. When a touch event is recognised it can delegate the action to whatever other object needs to deal with it. Having different views all trying to deal with touches at the same time is not a good way to deal with the problem. Gestures are dependent on other gestures and cannot all be handled independently by different views.
This is a pretty hypothetical question just to understand proper design but lets say I have two custom UIViews.
One of them is essentially a container that I'll call a drawer. Its purpose is to hide and show content. It's a lot like the notification center on iOS where you swipe to pull it open and flick it back up to close it. It's a generic container than can contain any other UIView. It has a UIPanGestureRecognizer to track the finger that's pulling it open/closed. It might also have a UISwipeGestureRecognizer to detect a "flick".
The other view is a custom map widget that has UIPan/Rotation/Pinch GestureRecognizers.
I think the drawer view should be the UIGestureRecognizerDelegate for the Pan/Swipe GestureRecognizers so that it can prevent touches from being delivered unless the user is grabbing "the handle".
My first instinct is for the map to be the UIGestureRecognizerDelegate of the pan/rotation/pinch gestures so that it can allow them to all run simultaneously.
The problem I'm having is that, I really don't want the map to receive any touches or begin recognizing gestures until the drawer is completely open. I'd like to be able to enforce this behavior automatically in the drawer itself so that it works for all subviews right out of the box.
The only way that I can think to do this is to wire all of the gestures handlers to the ViewController and let it do everything, but to me that breaks encapsulation as now it has to know that the map gestures need to run simultaneously, that the drawer should only get touches on it's handle and that the map should only get touches when it's open.
What are some ways of doing this where the logic can stay in the Views where I think it belongs?
I would do something like this to make the subviews of the drawer disabled while panning. Essentially loop through the drawer's subviews and disbale interaction on them.
[self.subviews enumerateObjectsUsingBlock:^(UIView *subview, NSUInteger idx, BOOL *stop){
subview.userInteractionEnabled = NO;
}];
And something similar again for when you want to re-enable user interaction on the subviews.
This should already Just Work™. A gesture recogniser is attached to a view; when a continuous gesture is recognised, all subsequent touches associated with that gesture are associated with that view.
So in your case, when the drawer pan is recognised, no touches associated with that pan should ever cause behaviour in your map view's pan/pinch/rotation gestures (unless you explicitly specify that they should using the appropriate delegate methods).
Or do you mean that you want to prevent the user from, halfway through opening the drawer, using another finger (i.e. another gesture) to start scrolling the (half-visible) map? If so, you should just set userInteractionEnabled on the drawer's contentView (or equivalent) to NO at UIGestureRecognizerStateBegan/Changed and YES again at UIGestureRecognizerStateEnded/Cancelled.
I am using a UIPanGestureRecogniser to implement drag and drop. When the drag starts I need to identify the object that is being dragged. However the objects are relatively small. And if the user doesn't hit the object right in the centre of the object it isn't getting dragged.
The problem is that when the gesture handler is first called with the state UIGestureRecognizerStateBegan, the finger has already moved several pixels, and so [UIPanGestureRecognizer locationInView:] returns that point, which is not where the gesture truly started. That makes sense as it can only recognize a pan after a few pixels of movement. However, I need the absolute start of the gesture, not the position after the gesture has first been recognized.
I'm thinking that maybe I need to implement a tap gesture recognizer as well, purely to capture the first touch. But that seems like a hack for what is not an unusual requirement. Is there no other way of getting that first touch from within the pan gesture recognizer?
UIGestureRecognizerDelegate protocol provides methods gestureRecognizerShouldBegin: and gestureRecognizer:shouldReceiveTouch: that can help you evaluate the touches before the pan has transitioned to state UIPanGestureRecognizerStateBegan
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 tried setting up a view with a longpress gesture and a stepper configured for continuous updates. With the longpress, the continuous feature of the stepper does not occur. For now, I've disabled the longpress. I guess I don't need it. But for future reference, how would I allow for both to coexist?
Just to be clear, here is the way the screen was set up when I tried this.
App was set up with a simple view controller.
A subview was added to this view (could have been a controller, but I just made it a UIView).
Several labels and stepper were added to this subview.
The steppers were wired up as outlets and actions.
A longpress recognizer was added to the main view in IB.
For completeness, a tap gesture was also added to the main view in IB.
Taps on the main view function as expected. Taps on the steppers function as expected. Longpress on the main view functions as expected. Longpress on the stepper does not.
I modified the code called by the longpress to check for the frame of the subview and not act if the touch location was within that rectangle, but that didn't make a difference. I did not try getting the longpress to fail in that situation, but I suppose I'll try that next. EDIT: OK, maybe not. There doesn't seem to be an API for that. However, there is this kludge, that I'm not going to try.
Attached is a screen shot from profiler with an inverted call tree so you can see what each item is being called by.
darkStepped: is the IBAction that is called by the stepper. If the stepper were triggered by a gesture recognizer, wouldn't I expect to see the gesture recognizer in the call tree?
If the stepper were triggered by a gesture recognizer, wouldn't I expect to see the gesture recognizer in the call tree?
The stack trace reveals that the stepper's _updateCount method is dispatched through a timer.
This could be related to the fact that a stepper has an "autoIncrement" mode where, as long as your keep it pressed, it will update at a given (varying) rate. So, instead of simply calling _updateCount, the stepper sets up a timer to handle this behaviour.
For whatever reason the timer is used, the timer explains why you do not see the gesture recogniser in the stack trace.
In your case what happens is that the stepper gets the touches, handles them, and do not forward them to any gesture recognisers attached to it.
This can be explained as follows, although this snippet does not explicitly mention a long press recogniser in relation to a UIStepper control:
According to Apple Docs:
Interacting with Other User Interface Controls
In iOS 6.0 and later, default control actions prevent overlapping gesture recognizer behavior. For example, the default action for a button is a single tap. If you have a single tap gesture recognizer attached to a button’s parent view, and the user taps the button, then the button’s action method receives the touch event instead of the gesture recognizer. This applies only to gesture recognition that overlaps the default action for a control, which includes:
A single finger single tap on a UIButton, UISwitch, UIStepper, UISegmentedControl, and UIPageControl.
...
If you have a custom subclass of one of these controls and you want to change the default action, attach a gesture recognizer directly to the control instead of to the parent view. Then, the gesture recognizer receives the touch event first. As always, be sure to read the iOS Human Interface Guidelines to ensure that your app offers an intuitive user experience, especially when overriding the default behavior of a standard control.
So, it seems you can attach the gesture recogniser directly to the control (possibly you need to subclass UIStepper for this to work, I am not really sure how to interpret the last paragraph). Hopefully this will not disable the basic workings of the stepper (but maybe it will).
After carefully reviewing Apple's docs again, I've found the solution. I added the view controller as the delegate to the longpress gesture recognizer
self.longPress.delegate = self;
(and, of course, adding <UIGestureRecognizerDelegate> to the interface, and then added this method to the view controller:
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
// Determine if the touch is inside the custom subview
if (gestureRecognizer == self.longPress) {
CGPoint touchLocation = [touch locationInView:self.view];
if (CGRectContainsPoint(self.antControl.frame, touchLocation)) {
return NO;
}
}
return YES;
}
This way the gesture recognizer doesn't even get called when the longpress occurs within the frame of self.antControl, which is the subview mentioned in the question.