PMCircularCollectionView is a subclass of UICollectionView that scrolls infinitely in the horizontal or vertical direction. PMCircularCollectionView also includes a subclass which automatically centers the cell nearest to the middle of the collection view after scrolling.

Requirements & Notes

• PMCircularCollectionView was built for iOS and requires a minimum iOS target of iOS 7.
• Thorough commenting of header files is currently in progress. (6/11/14).
• PMCircularCollectionView is currently lacking unit tests.

How To Get Started

• Check out the documentation (coming soon).

Podfile

platform :ios, '7.0'
pod "PMCircularCollectionView"

Usage

Creating a PMCircularCollectionView

PMCenteredCollectionViewFlowLayout *layout = [UICollectionViewFlowLayout new];
layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
layout.minimumLineSpacing = 10; 
layout.minimumInteritemSpacing = 0;

PMCenteredCircularCollectionView *collectionView = [PMCircularCollectionView collectionViewWithFrame:self.view.bounds collectionViewLayout:layout];
collectionView.delegate = self;
collectionView.dataSource = self;

UICollectionViewDataSource

- (UICollectionViewCell *) collectionView:(PMCenteredCircularCollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:PMCellReuseIdentifier forIndexPath:indexPath];
    NSInteger normalizedIndex = [collectionView normalizeIndex:indexPath.item];
    /*
    * Configure cell based on indexPath.section and normalizedIndex.
    */
}

Discussion

• To achieve infinite scrolling, PMCircularCollectionView employes a technique described in this blog post which multiplies the content size and consequently the number of index paths. Thus, it is possible for dataSource and delegate methods to pass an index path with item == 15, when less than 16 items were returned to the -collectionView:numberOfItemsInSection: delegate method. As seen in the examples above, call -normalizeIndex: to change the item index to the correct value.
• -numberOfSectionsInCollectionView: will never be called. PMCircularCollectionView only supports 1 section.

Creating a PMCenteredCircularCollectionView

PMCenteredCollectionViewFlowLayout *layout = [PMCenteredCollectionViewFlowLayout new];
layout.centeringDisabled = NO;
layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
layout.minimumLineSpacing = 10; 
layout.minimumInteritemSpacing = 0;

PMCenteredCircularCollectionView *collectionView = [PMCenteredCircularCollectionView collectionViewWithFrame:self.view.bounds collectionViewLayout:layout];
collectionView.delegate = self;
collectionView.dataSource = self;

PMCenteredCircularCollectionViewDelegate

- (void) collectionView:(PMCenteredCircularCollectionView *)collectionView didCenterItemAtIndex:(NSUInteger)index
{
    NSUInteger normalizedIndex = [collectionView normalizeIndex:index];
    NSLog(@"Collection View: %@\nDid center item at index %d", collectionView, normalizedIndex);
}

Communication

• If you need help, use Stack Overflow. (Tag 'PMCircularCollectionView')
• If you'd like to ask a general question, use Stack Overflow.
• If you found a bug, open an issue.
• If you have a feature request, open an issue.
• If you want to contribute, submit a pull request.

Author

• Peter Meyers

License

PMCircularCollectionView is available under the MIT license. See the LICENSE file for more info.