Hijack "swipe to next page" in UIScrollView - objective-c

Question

i'd like to prevent scrolling on the 3rd page of my UIScrollview and "hijack the swipe" gesture to trigger sth. else. Afer this action I'd like to reactive scrolling.
This does not work.
- (void)scrollViewDidScroll:(UIScrollView *)sender
{
if(scrollView.contentOffset.x == self.view.frame.size.width * 2 ) {
// disable scrolling
scrollView.scrollEnabled = NO;
}
}
// hijack the next scrolling event
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
This delegate is not called when scrollEnabled = NO
Thanks for helping
EDIT EventHandler ist not called ;-(
- (void)viewDidLoad
{
[super viewDidLoad];
// Default background color
self.view.backgroundColor = [UIColor redColor];
// Create scroll view
scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
scrollView.pagingEnabled = YES;
scrollView.showsHorizontalScrollIndicator = NO;
scrollView.showsVerticalScrollIndicator = NO;
scrollView.scrollsToTop = NO;
scrollView.delegate = self;
UISwipeGestureRecognizer *recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(handleSwipeFrom:)];
recognizer.direction = UISwipeGestureRecognizerDirectionLeft;
[scrollView addGestureRecognizer:recognizer];
[recognizer release];
[scrollView delaysContentTouches];
// Create subviews (pages)
NSInteger numberOfViews = 4;
for (int i = 0; i < numberOfViews; i++) {
// x pos
CGFloat yOrigin = i * self.view.frame.size.width;
// Create subview and add to scrollView
UIView *pageView = [[UIView alloc] initWithFrame:CGRectMake(yOrigin, 0, self.view.frame.size.width, self.view.frame.size.height)];
pageView.backgroundColor = [UIColor colorWithRed:0.5/i green:0.5 blue:0.5 alpha:1];
[scrollView addSubview:pageView];
[pageView release];
}
// Set contentsize
scrollView.contentSize = CGSizeMake(self.view.frame.size.width * numberOfViews, self.view.frame.size.height);
// Add scrollView to view and release
[self.view addSubview:scrollView];
[scrollView release];
}
-(void)handleSwipeFrom:(UISwipeGestureRecognizer *)recognizer {
NSLog(#"swipe!!!!");
scrollView.scrollEnabled = YES;
}

Answer 1

If you disable the scroll view:
scrollView.scrollEnabled = NO;
it is unavoidable that the delegate method is not called, so you need an alternative way to handle the swipe while in hijack mode. One thing you could try is using an UISwipeGestureRecognizer: instead of simply disabling scrolling, you could associate a UISwipeGestureRecognizer to you view and handle the swipe from the handler method:
UISwipeGestureRecognizer *recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:#selector(handleSwipeFrom:)];
recognizer.direction = UISwipeGestureRecognizerDirectionRight;
[self.view addGestureRecognizer:recognizer];
and in handleSwipeFrom you would reenable scrolling:
-(void)handleSwipeFrom:(UISwipeGestureRecognizer *)recognizer {
// do your hijack here
scrollView.scrollEnabled = YES;
}