UIPanGestureRecognizer interfering with scroll - ios

Question

I have a scroll view with 3 view controllers that I want to swipe between. However, one of my view controllers has a UIPanGestureRecognizer and this stops the scrollview from working. This is the code for the pan:
- (void)pan:(UIPanGestureRecognizer *)aPan; // When pan guesture is recognised
{
CGPoint location = [aPan locationInView:self.view]; // Location of finger on screen
CGRect secondRect = CGRectMake(210.0, 45.0, 70.0, 325.0); // Rectangles of maximimum bar area
CGRect minuteRect = CGRectMake(125.0, 45.0, 70.0, 325.0);
CGRect hourRect = CGRectMake(41.0, 45.0, 70.0, 325.0);
if (CGRectContainsPoint(secondRect, location)) { // If finger is inside the 'second' rectangle
CGPoint currentPoint = [aPan locationInView:self.view];
currentPoint.y -= 80; // Make sure animation doesn't go outside the bars' rectangle
if (currentPoint.y < 0) {
currentPoint.y = 0;
}
else if (currentPoint.y > 239) {
currentPoint.y = 239;
}
currentPoint.y = 239.0 - currentPoint.y;
CGFloat pointy = currentPoint.y - fmod(currentPoint.y, 4.0);
[UIView animateWithDuration:0.01f // Animate the bars to rise as the finger moves up and down
animations:^{
CGRect oldFrame = secondBar.frame;
secondBar.frame = CGRectMake(oldFrame.origin.x, (oldFrame.origin.y - (pointy - secondBar.frame.size.height)), oldFrame.size.width, (pointy));
}];
CGFloat result = secondBar.frame.size.height - fmod(secondBar.frame.size.height, 4.0);
secondInt = (result / 4.0); // Update labels with new time
self->secondLabel.text = [NSString stringWithFormat:#"%02d", secondInt];
}
}
Basically, this code allows the user to drag their finger up and down the screen, and change the height of a uiview. Therefore, I only need the up/down pan gesture for this and only the left/right pan gestures for the scroll view.
Does anyone have any idea how I can do this?

Answer 1

Your scrollview has a property called panGestureRecognizer. You can create a delegate for your own UIPanGestureRecognizer, and implement this method:
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
if(otherGestureRecognizer == myScrollView.panGestureRecognizer) {
return YES;
} else {
return NO;
}
}

Answer 2

UIPanGestureRecognizer contains a delegate method - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch that you can return YES or NO to let/prevent the pan gesture from receiving the touch.
Within that method, you could write something like:
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
CGPoint velocity = [gestureRecognizer velocityInView:yourView];
if(velocity.x > 0)
{
NSLog(#"gesture went right"); // return NO
}
else if (velocity.x < 0)
{
NSLog(#"gesture went left"); // return NO
}
if (velocity.y > 0)
{
NSLog(#"gesture went down"); // return YES
}
else if (velocity.y < 0)
{
NSLog(#"gesture went up"); // return YES
}
}
Admittedly, that probably isn't the cleanest implementation. You're leaving an open door for mixed gestures. So just make sure to watch for that.