Detect swiping in UICollectionView - iphone

Question

I need to perform a specific action when the user swipes the uicollectionview.
I built it in a way that each cell captures the full screen.
I tried those ways:
A. scrollViewDidEndDecelerating
# pragma UIScrollView
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
NSLog(#"detecting scroll");
for (UICollectionViewCell *cell in [_servingTimesCollectionView visibleCells]) {
NSIndexPath *indexPath = [_servingTimesCollectionView indexPathForCell:cell];
CGPoint scrollVelocity = [scrollView.panGestureRecognizer velocityInView:_servingTimesCollectionView];
if (scrollVelocity.x > 0.0f)
NSLog(#"going right");
else if (scrollVelocity.x < 0.0f)
NSLog(#"going left");
}
}
But the scrollVelocity returns null. The method is being called.
B. UISwipeGestureRecognizer
In ViewDidLoad of my UIViewController which delegates to UICollectionViewDataSource and UIGestureRecognizerDelegate I added:
UISwipeGestureRecognizer *swipeRight = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(didSwipeRight:)];
swipeRight.numberOfTouchesRequired = 1;
[swipeRight setDirection:UISwipeGestureRecognizerDirectionRight];
UISwipeGestureRecognizer *swipeLeft = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(didSwipeLeft:)];
swipeRight.numberOfTouchesRequired = 1;
[swipeRight setDirection:UISwipeGestureRecognizerDirectionRight];
[_servingTimesCollectionView addGestureRecognizer:swipeRight];
[_servingTimesCollectionView addGestureRecognizer:swipeLeft];
and the followings in the UiViewController:
#pragma mark - UISwipeGestureRecognizer Action
-(void)didSwipeRight: (UISwipeGestureRecognizer*) recognizer {
NSLog(#"Swiped Right");
}
-(void)didSwipeLeft: (UISwipeGestureRecognizer*) recognizer {
NSLog(#"Swiped Left");
}
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
NSLog(#"Asking permission");
return YES;
}
But none are called.
What is wrong? I am developing for ios7

Answer 1

You are not setting the delegate of the gestures:
UISwipeGestureRecognizer *swipeRight = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(didSwipeRight:)];
swipeRight.delegate = self;
swipeRight.numberOfTouchesRequired = 1;
[swipeRight setDirection:UISwipeGestureRecognizerDirectionRight];
UISwipeGestureRecognizer *swipeLeft = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(didSwipeLeft:)];
swipeLeft.delegate = self;
swipeLeft.numberOfTouchesRequired = 1;
[swipeLeft setDirection:UISwipeGestureRecognizerDirectionLeft];

Answer 2

i was trying to do same thing with you (by full size cell frames in a UICollectionView). Just delegating with self is not sufficient enought, because UICollectionView may has it's own gesture recognizer. So below trick was worked in may case.
override func viewDidLoad() {
super.viewDidLoad()
collectionView?.backgroundColor = .red
let leftGR = UISwipeGestureRecognizer(target: self, action: #selector(self.swipeHandler_Left(gestureRecognizer:)))
leftGR.numberOfTouchesRequired = 1
leftGR.direction = .left
leftGR.delegate = self
self.view.addGestureRecognizer(leftGR)
}
#objc func swipeHandler_Left(gestureRecognizer : UISwipeGestureRecognizer!) {
if gestureRecognizer.state == .ended {
// Perform action.
print("***Free to Delete Old Cell")
}
}
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
return true
}
sorry for my swifty answer, pls try to translate objc :)