Capture only UIView 2 finger UIPanGestureRecognizer - ios

Question

I have a couple of UIScrollViews in my view controller. I want to overlay a view that captures a 2 finger swipe via UIPanGestureRecognizer which will not record the UIScrollView swipe gestures.
When I put a transparent view over my content with a 2 finger pan gesture, my taps and 1 finger swipes are not detected. I tried overwriting the pointInside: method to return NO
but then it doesn't record my 2 finger swipe.
The effect is similar to the 4 finger swipe to change apps.

Answer 1

You don't need an overlay view.
First implement UIPanGestureRecognizer that will handle 2 finger pan and assign it to your view that contains UIScrollViews
UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc]
initWithTarget:self
action:#selector(handlePan:)];
panGestureRecognizer.delegate = self;
panGestureRecognizer.minimumNumberOfTouches = 2;
panGestureRecognizer.maximumNumberOfTouches = 2;
[self.view addGestureRecognizer:panGestureRecognizer];
Use UIGestureRecognizerDelegate to handle 2 finger pan with UIScrollView pan gesture
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
return YES;
}
And finally you are able to handle 2 fingers pan
- (void)handlePan:(UIPanGestureRecognizer *)gestureRecognizer
{
NSLog(#"pan");
}
If you want to stop scrolling UIScrollView when two finger pan is detected you can disable and enable UIScrollView pan recognizers
- (void)handlePan:(UIPanGestureRecognizer *)gestureRecognizer
{
if(gestureRecognizer.state == UIGestureRecognizerStateBegan)
{
_scrollView.panGestureRecognizer.enabled = NO;
}
if(gestureRecognizer.state == UIGestureRecognizerStateEnded)
{
_scrollView.panGestureRecognizer.enabled = YES;
}
NSLog(#"pan");
}

Answer 2

If you don't really need the overlay you can solve this with just gesture recognizers. I wrote this up as a test:
- (void)viewDidLoad {
[super viewDidLoad];
self.scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
_scrollView.contentSize = CGSizeMake(self.view.bounds.size.width * 2, self.view.bounds.size.height);
UIView *green = [[UIView alloc] initWithFrame:self.view.bounds];
[green setBackgroundColor:[UIColor greenColor]];
UIView *blue = [[UIView alloc] initWithFrame:CGRectOffset(self.view.bounds, self.view.bounds.size.width, 0)];
[blue setBackgroundColor:[UIColor blueColor]];
[_scrollView addSubview:green];
[_scrollView addSubview:blue];
UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(twoFingerPan:)];
[pan setMinimumNumberOfTouches:2];
[pan setMaximumNumberOfTouches:2];
[pan setDelaysTouchesBegan:YES];
[_scrollView addGestureRecognizer:pan];
[self.view addSubview:_scrollView];
}
- (void)twoFingerPan:(UIPanGestureRecognizer *)gesture {
switch (gesture.state) {
case UIGestureRecognizerStateBegan:
self.scrollView.scrollEnabled = NO;
break;
case UIGestureRecognizerStateCancelled:
case UIGestureRecognizerStateEnded:
case UIGestureRecognizerStateFailed:
self.scrollView.scrollEnabled = YES;
break;
default:
break;
}
NSLog(#"2 Fingers!");
}
I get the twoFingerPan: call back for when 2 fingers are used. The scroll view's panGestureRecognizer is still working at that point so I disable scrolling on the scroll view to handle the 2 finger pan. I've found this method work's pretty well. One sort of wonky thing is if the scroll view is decelerating the 2 finger gesture recognizer isn't called. Hope that helps!