ARCollectionViewMasonryLayout 2.2.0

ARCollectionViewMasonryLayout 2.2.0

TestsTested
LangLanguage Obj-CObjective C
License MIT
ReleasedLast Release Feb 2016

Maintained by Eloy Durán, Orta Therox, Ash Furrow, Laura Brown.


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  • By
  • Orta Therox and Ash Furrow

ARCollectionViewMasonryLayout is a UICollectionViewLayout subclass for creating flow-like layouts with dynamic widths or heights.

Screenshot

Usage

Create an instance of a ARCollectionViewMasonryLayout.

ARCollectionViewMasonryLayout *layout = [[ARCollectionViewMasonryLayout alloc] initWithDirection:ARCollectionViewMasonryLayoutDirectionVertical];

Create a collection view. Its delegate must conform to the ARCollectionViewMasonryLayoutDelegate protocol in order to retrieve the variable dimensions of the cells.

@interface ARCollectionViewController : UICollectionViewController

@end
@interface ARCollectionViewController () <ARCollectionViewMasonryLayoutDelegate>

@end

@implementation ARCollectionViewController

#pragma mark - UIViewController Lifecycle and Callbacks

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"Cell"];
}

#pragma mark - UICollectionViewDataSource Methods

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 10;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    CGFloat colorSeed = (indexPath.row * 3 % 255)/255.0f; // random-ish color
    cell.backgroundColor = [UIColor colorWithRed:colorSeed green:colorSeed blue:colorSeed alpha:1];
    return cell;
}

#pragma mark - ARCollectionViewMasonryLayoutDelegate Methods

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(ARCollectionViewMasonryLayout *)collectionViewLayout variableDimensionForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return (CGFloat)(indexPath.row * 10 % 30) + 40; // random-ish varying size
}

@end

Headers and Footers

The masonry layout supports a fixed height header and footer that scroll along with the contents of the view. These can be added by implementing the following delegate methods on the UIViewController.

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    // return a header and/or footer view, must be a UICollectionReusableView
    // kind is one of UICollectionElementKindSectionHeader or UICollectionElementKindSectionFooter
    UICollectionReusableView *view = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:kind forIndexPath:indexPath];
    view.backgroundColor = [UIColor whiteColor];
    return view;
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(ARCollectionViewMasonryLayout *)collectionViewLayout dimensionForHeaderAtIndexPath:(NSIndexPath *)indexPath
{
    return 20; // header length
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(ARCollectionViewMasonryLayout *)collectionViewLayout dimensionForFooterAtIndexPath:(NSIndexPath *)indexPath
{
    return 10; // footer length
}

Sticky Headers

The layout supports having a custom sticky header ( similar to the ones in a UITableView. ) It behaves simiar to how Headers and footers work. However it needs the layout delegate to support collectionView:layout:referenceSizeForStickyHeaderInSection:.

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    [..]
    } if ([kind isEqualToString:ARCollectionElementKindSectionStickyHeader]) {
        UICollectionReusableView *view = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:kind forIndexPath:indexPath];
        view.backgroundColor = [UIColor purpleColor];
        return view;

    }
    [..]
}


- (CGSize)collectionView:(UICollectionView *)collectionView layout:(ARCollectionViewMasonryLayout *)collectionViewLayout referenceSizeForStickyHeaderInSection:(NSInteger)section
{
    return self.stickyHeaderSize;
}

It also provides a callback incase you want to make transitions when the header is sticky or not:

- (void)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout stickyHeaderHasChangedStickyness:(BOOL)isAttachedToLeadingEdge
{
    NSLog(@"Attatched: %@", @(isAttachedToLeadingEdge));
}

Demo Project

This repository contains a demo project showing the use of the collection view layout. The view controller creates a number of ARModel instances which represent a color and dimension of a cell. These values are assigned from a collection of colors in viewDidLoad. When the collection view asks for a cell, the cell's background colour is set to the corresponding model's color. The layout queries the collection view's delegate for dimension information, and the corresponding model's dimension is returned.

License

Licensed under MIT.

Credits

Originally created by Orta for Artsy.