UIPanGestureRecognizer conflict with scrollview - ios

Question

I'm trying to add a pan gesture recognizer to a view containing a scrollview, but I guess I've problems with priorities.
My global UIView has a UIPanGestureRecognizer set like this:
_bottomPanGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(bottomPanGestureDetected:)];
_bottomPanGestureRecognizer.minimumNumberOfTouches = 2;
_bottomPanGestureRecognizer.maximumNumberOfTouches = 2;
_bottomPanGestureRecognizer.delaysTouchesBegan = NO;
_bottomPanGestureRecognizer.delaysTouchesEnded = NO;
I want to recognize this gesture to display another view from the bottom with some sort of pinch down-to-up.
The problem is that the scrollview is recognizing its own pan gesture before mine.
So I tried to delay it thanks to:
[_scrollView.panGestureRecognizer requireGestureRecognizerToFail:_bottomPanGestureRecognizer];
And it's working, the scrollview event is fired after my two finger down to up recognizer, but the problem is now when I only use one finger to scroll in the scrollview, the scroll works after a small delay.
I would like to have no delay for this event, is this possible? Any idea welcomed!
Cheers.
Cyril

Answer 1

In case it isn't solved yet, i solved the problem for me.
I added a UIPanGestureRecognizer to a UIScrollView to detect two finger pan gestures and the default UIScrollView behaviour (scrolling to something) still workes.
So what i did is to add the UIPanGestureReconizer to the UIScrollView:
UIPanGestureRecognizer *pangestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(displayReloadIndicator:)];
pangestureRecognizer.minimumNumberOfTouches = 2;
pangestureRecognizer.delegate = self;
[self.scrollView addGestureRecognizer:pangestureRecognizer];
[pangestureRecognizer release];
After this i added the code:
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
return YES;
}
After this, i implemented the pan gesture recognizers action method.
- (void) displayReloadIndicator:(UIPanGestureRecognizer*) panGestureRecognizer {
UIGestureRecognizerState gestureRecognizerState = gestureRecognizer.state;
CGPoint translation = [gestureRecognizer translationInView:self.scv_bibgesamt];
if (gestureRecognizerState == UIGestureRecognizerStateBegan) {
// create a UIView with all the Pull Refresh Headers and add to UIScrollView
// This is really much lines of code, but its simply creating a UIView (later you'll find a myRefreshHeaderView, which is my base view) and add UIElements e.g. UIActivityIndicatorView, a UILabel and a UIImageView on it
// In iOS 6 you will also have the possibility to add a UIRefreshControl to your UIScrollView
}
else if (gestureRecognizerState == UIGestureRecognizerStateEnded
|| gestureRecognizerState == UIGestureRecognizerStateCancelled) {
if (translation.y >= _myRefreshHeaderView.frame.size.height + 12) { // _myRefreshHeaderView is my baseview
//so the UIScrollView has been dragged down with two fingers over a specific point and have been release now, so we can refresh the content on the UIScrollView
[self refreshContent];
//animatly display the refresh view as the top content of the UIScrollView
[self.scrollView setContentOffset:CGPointMake(0, myRefreshHeaderView.frame.size.height) animated:YES];
}
else {
//the UIScrollView has not been dragged over a specific point so don't do anything (just scroll back to origin)
[self.scrollView setContentOffset:CGPointMake(0, 0) animated:YES];
//remove the view (because it's no longer needed)
[_myRefreshHeaderView removeFromSuperview];
}
}
UPDATE:
In case you may wish to integrate the swipe back functionality from your navigationcontroller, you should integrate following code:
- (void) viewDidLoad {
[super viewDidLoad];
if ([self.navigationController respondsToSelector:#selector(interactivePopGestureRecognizer)]) {
self.navigationController.interactivePopGestureRecognizer.enabled = YES;
self.navigationController.interactivePopGestureRecognizer.delegate = nil;
}
//setup view controller
}
and
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
if (gestureRecognizer == _panGestureRecognizer
&& [self.navigationController.viewControllers count] > 1) {
CGPoint point = [touch locationInView:self.view.window];
if (point.x < 20
|| point.x > self.view.window.frame.size.width - 20) {
return NO;
}
}
return YES;
}

Answer 2

Implement panRecognizer delegate to enable simultaneously recognize UIScrollView UIGestureRecognizer
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
if (_panRecognizer == gestureRecognizer) {
if ([otherGestureRecognizer.view isKindOfClass:UIScrollView.class]) {
UIScrollView *scrollView = (UIScrollView *)otherGestureRecognizer.view;
if (scrollView.contentOffset.x == 0) {
return YES;
}
}
}
return NO;
}

Answer 3

SWIFT 4
If using a scrollView you can use below, it is only a panGestureRecognizer when a scrollView is dragging at the very top:
translation.y > 0 means you are moving from top to bottom and
locationInScrollView.y < 500.0 means you end dragging at 500 or less (you can customize this) to prevent that the refresh is done in middle or bottom of the scroll.
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
let translation = scrollView.panGestureRecognizer.translation(in: scrollView.superview)
let locationInScrollView = scrollView.panGestureRecognizer.location(in: scrollView)
if translation.y > 0 && locationInScrollView.y < 500.0 {
print("scrollView refresh: Y: \(locationInScrollView.y)")
setupUI()
}
}