Scrolling goes to wrong direction in iCarouselTypeLinear

[ramrcram]

Hi Nick, am developing an iPad application using iCarousel. first of all thanks for the wonderful component . Am facing a problem with ITEM_SPACING = 860, wrap = YES,carousel.type =iCarouselTypeLinear,ignorePerpendicularSwipes = YES. some time when we scroll from left to right or other way the item move to the wrong direction. This is what i done on viewForItemAtIndex

- (UIView *)carousel:(iCarousel *)carousel viewForItemAtIndex:(NSUInteger)index reusingView:(UIView *)view
{
    NSString* ImageName = @"Sample.jpg";
    UIButton *button = (UIButton *)view;
    if (button == nil)
    {
        UIImage *image = [UIImage imageNamed:ImageName];
        button = [UIButton buttonWithType:UIButtonTypeCustom];
        button.frame = (UIDeviceOrientationIsPortrait(self.interfaceOrientation) ?CGRectMake(0,0,610,456) : CGRectMake(0,0,830,620));
        [button setBackgroundImage:image forState:UIControlStateNormal];
        [button addTarget:self action:@selector(categoryImageClicked:) forControlEvents:UIControlEventTouchUpInside];
    }    
    return button;

}

please help me to fix this problem Thanks in advance.

[nicklockwood]

Are all of your carousel images the same? Because if not, the code above won't work as you are recycling the same view for multiple items.

[ramrcram]

No ,the images are different , for the easy understand i added the like that, the actual code is getting from nsdictionary. NSString* ImageName = [carouselDic objectForKey:@"imageName"];

[nicklockwood]

Okay, so then your code needs to look this this:

- (UIView *)carousel:(iCarousel *)carousel viewForItemAtIndex:(NSUInteger)index reusingView:(UIView *)view
{
    NSString* ImageName = @"Sample.jpg";
    UIButton *button = (UIButton *)view;
    if (button == nil)
    {
        button = [UIButton buttonWithType:UIButtonTypeCustom];
        button.frame = (UIDeviceOrientationIsPortrait(self.interfaceOrientation) ?CGRectMake(0,0,610,456) : CGRectMake(0,0,830,620));
        [button addTarget:self action:@selector(categoryImageClicked:) forControlEvents:UIControlEventTouchUpInside];
    }

    UIImage *image = [UIImage imageNamed:ImageName];
    [button setBackgroundImage:image forState:UIControlStateNormal];

    return button;
}

Views are recycled like in a tableview, so you need to set the image property each time regardless of whether there is a view available to re-use as the reusable view may have previously been set with the image for a different item in the carousel.

[ramrcram]

Hi Nick, i found the issue what wrong. While am scrolling it's triggering on the event

• (void)didPan:(UIPanGestureRecognizer *)panGesture. I checked the panGesture.state, for the normal scroll the state (Correct direction) is coming with UIGestureRecognizerStateChanged, but while wrong scroll (wrong direction)the state UIGestureRecognizerStateChanged not happing.

so that what i done for the fix is, just removed the default section from the switch case on didPan function and moved out side of switch now my didPan function is like :

- (void)didPan:(UIPanGestureRecognizer *)panGesture
{
if (scrollEnabled)
    {
    switch (panGesture.state)
    {
        case UIGestureRecognizerStateBegan:
        {
            dragging = YES;
            scrolling = NO;
            decelerating = NO;
            previousTranslation = vertical? [panGesture translationInView:self].y: [panGesture translationInView:self].x;
            if ([delegate respondsToSelector:@selector(carouselWillBeginDragging:)])
            {
                [delegate carouselWillBeginDragging:self];
            }
            break;
        }
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled:
        {
            dragging = NO;
            didDrag = YES;
            if ([self shouldDecelerate])
            {
                didDrag = NO;
                [self startDecelerating];
            }
            if ([delegate respondsToSelector:@selector(carouselDidEndDragging:willDecelerate:)])
            {
                [delegate carouselDidEndDragging:self willDecelerate:decelerating];
            }
            if (!decelerating && (scrollToItemBoundary || (scrollOffset - [self clampedOffset:scrollOffset]) != 0.0f))
            {
                if (fabsf(scrollOffset/itemWidth - self.currentItemIndex) < 0.01f)
                {
                    //call scroll to trigger events for legacy support reasons
                    //even though technically we don't need to scroll at all
                    [self scrollToItemAtIndex:self.currentItemIndex duration:0.01];
                }
                else if ([self shouldScroll])
                {
                    NSInteger direction = (int)(startVelocity / fabsf(startVelocity));
                    [self scrollToItemAtIndex:self.currentItemIndex + direction animated:YES];
                }
                else
                {
                    [self scrollToItemAtIndex:self.currentItemIndex animated:YES];
                }
            }
            else if ([delegate respondsToSelector:@selector(carouselWillBeginDecelerating:)])
            {
                [delegate carouselWillBeginDecelerating:self];
            }
            break;
        }
        default:
        {}
       }
        CGFloat translation = (vertical? [panGesture translationInView:self].y: [panGesture translationInView:self].x) - previousTranslation;
        CGFloat factor = 1.0f;
        if (!shouldWrap && bounces)
        {
            factor = 1.0f - fminf(fabsf(scrollOffset - [self clampedOffset:scrollOffset]) / itemWidth, bounceDistance) / bounceDistance;
        }
        previousTranslation = vertical? [panGesture translationInView:self].y: [panGesture translationInView:self].x;
        startVelocity = -(vertical? [panGesture velocityInView:self].y: [panGesture velocityInView:self].x) * factor * scrollSpeed;
        scrollOffset -= translation * factor * offsetMultiplier;
        [self didScroll];   
    }
}

please let me know is anything wrong on my updated function ?

Thanks in advance Ramesh

[nicklockwood]

I'm not really sure why this would cause the carousel to go backwards. I'll have to check and see if I can work out if this fix has any other side effects.

[ramrcram]

Thanks Nick.