iOS: UICollectionView repeat NSMutableArray value in circular way - ios

Question

How can I repeat NSMutableArray value in UICollectionView and scroll automatically from top to bottom for gaming like effect?
For example if I have array with 10 elements and wants to repeat all 10 value in UICollectionView with 4 cells in a row and scroll from top to bottom continuously.
Currently I am adding 200 values statically in NSMutableArray and than applying NSTimer on that. But I want to repeat 10 values again and again.
How can I do that?
code given below is to call on NSTimer for scrolling
[collectionview setUserInteractionEnabled:NO];
CGFloat h = collectionview.contentOffset.y;
h += 10;
CGFloat h2 = 10;
h2 += 10;
CGPoint bottomOffset = CGPointMake(0, h - h2);
[collectionview setContentOffset:bottomOffset animated:YES];
int dd = collectionview.contentOffset.y;
NSLog(#"dd timer....%d" ,dd);
if (dd <= 0) {
}

Answer 1

I have a similar situation where I continuously scroll a collection of images. What I did was in collectionView:numberOfItemsInSection: was return INT_MAX. Then in collectionView:cellForItemAtIndexPath:, just mod the row by the size of your NSMutableArray and use that as the index into your array to create the UICollectionViewCell. It doesn't scroll backwards from the top of the list, and it isn't exactly "infinite", but it sure does provied a LOT of cells. I suppose if you wanted to start in the middle and allow scrolling backwards, you could just scroll the collection view to some cell that makes sense in the middle of the collection.
Example implementation:
#interface CollectionViewController ()
#property (nonatomic, strong) NSArray<NSString*>* objects;
#end
#implementation CollectionViewController
static NSString * const reuseIdentifier = #"Cell";
- (void)viewDidLoad
{
[super viewDidLoad];
_objects = #[#"One", #"Two", #"Three", #"Four", #"Five", #"Six", #"Seven", #"Eight", #"Nine", #"Ten"];
}
#pragma mark <UICollectionViewDataSource>
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return INT_MAX;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
CollectionViewCell* cell = (CollectionViewCell*)[collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];
NSInteger index = indexPath.row % self.objects.count;
NSString* str = self.objects[index];
[cell.label setText:str];
return cell;
}
#end
I don't know for sure what the performance impact of this is, but since UICollectionView only loads as many cells as it needs, I don't believe it to be too impactful. It works well for me.
If true circular scrolling is important, you could try an open-source solution (ex. https://cocoapods.org/pods/PMCircularCollectionView)

Answer 2

You can try this:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView_
{
CGFloat actualPosition = scrollView_.contentOffset.y;
CGFloat contentHeight = scrollView_.contentSize.height - (someArbitraryNumber);
if (actualPosition >= contentHeight) {
[yourMutableArray addObjectsFromArray: yourMutableArray];
[yourCollectionView reloadData];
}
}