I have created this infinite collectionView loop with 13 icons, however it's not working properly on 320 x 568 resolution devices. The issue is with calculating appropriate image contentOffset when scrolling (it's an animation - it's not touchable) and it's not centered after a while. Those images are equally spaced between as I want to show 3 icons on screen at once. When 3 icons passes previousContentOffset is x = 319.5 and it should be x = 320.0 Any suggestions of workaround for this particular case? Perhaps iterate by single icon? Results I am getting after 1 icon slide:
previousContentOffset = (CGPoint)(x = 106.5, y = 0),
width = (double)106.66666666666667,
currentContentOffset = (CGPoint)(x = 213.16666666666669, y = 0)
// Infinite loop
- (void)setupDataForCollectionView {
NSArray *originalArray = self.arrayImages;
NSMutableArray *workingArray = [originalArray mutableCopy];
self.dataArray = [workingArray mutableCopy];
}
// Implementation of infinite loop
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
// calculate width for every device
double contentOffsetWhenFullyScrolledRight = self.collectionViewHorizontal.contentSize.width - self.collectionViewHorizontal.frame.size.width;
if (scrollView.contentOffset.x == contentOffsetWhenFullyScrolledRight) {
NSIndexPath *newIndexPath = [NSIndexPath indexPathForItem:1 inSection:0];
[self.collectionViewHorizontal scrollToItemAtIndexPath:newIndexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:NO];
} else if (scrollView.contentOffset.x == 0) {
NSIndexPath *newIndexPath = [NSIndexPath indexPathForItem:([self.dataArray count] -2) inSection:0];
[self.collectionViewHorizontal scrollToItemAtIndexPath:newIndexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:NO];
}
}
// TimeInterval for animation
- (void)timerAction:(NSTimer *)timer {
//previous icon content offset
CGPoint previousContentOffSet = self.collectionViewHorizontal.contentOffset;
//next icon width
double width = self.collectionViewHorizontal.frame.size.width / 3;
// NSUInteger index = (int)(floor(self.collectionViewHorizontal.contentOffset.x / width) + 1);
// animate icons scroll view
CGPoint currentContentOffset = CGPointMake(previousContentOffSet.x + width, previousContentOffSet.y);
NSIndexPath *indexPath = [self.collectionViewHorizontal indexPathForItemAtPoint:currentContentOffset];
if (indexPath.row > self.dataArray.count - 4) {
// add elements and reload
[self.dataArray addObjectsFromArray:[self.arrayImages copy]];
[self.collectionViewHorizontal reloadData];
}
// sliding animation
[UIView animateWithDuration:.3 delay:.0 usingSpringWithDamping:0.5 initialSpringVelocity:.0 options:kNilOptions animations:^{
self.collectionViewHorizontal.contentOffset = currentContentOffset;
} completion:^(BOOL finished) {
[self scrollViewDidEndDecelerating:self.collectionViewHorizontal];
}];
}
I have implemented a workaround a while back, so I thought I should share. I decided to iterate with indexes of current icon instead of contentOffset. I have created a NSInteger property currentIndex and added in timer method.
- (void)timerAction:(NSTimer *)timer {
self.currentIndex++;
//next icon width
double width = self.collectionViewHorizontal.frame.size.width / 3;
// animate icons scroll view
CGPoint currentContentOffset = CGPointMake(self.currentIndex * width, 0.0);
NSIndexPath *indexPath = [self.collectionViewHorizontal indexPathForItemAtPoint:currentContentOffset];
if (indexPath.row > (self.dataArray.count /2) {
// add elements and reload
[self.dataArray addObjectsFromArray:[self.arrayImages copy]];
[self.collectionViewHorizontal reloadData];
}
// sliding animation
[UIView animateWithDuration:.3 delay:.0 usingSpringWithDamping:0.5 initialSpringVelocity:.0 options:kNilOptions animations:^{
self.collectionViewHorizontal.contentOffset = currentContentOffset;
} completion:^(BOOL finished) {
[self scrollViewDidEndDecelerating:self.collectionViewHorizontal];
}];
}