iOS iPhone - UICollectionView reloading wrong UICollectionViewCell at indexPath

Question

I have a custom UICollectionView subclass and custom UICollectionViewCells. Problem is that When I scroll the collection view, it changes the position of the items like this:

Before scroll -

After scroll down and then back to top - (notice how Modesto and Rebecka changed postions)

The UICollectionView subclass is pretty clear :

#import "MyCustomCollectionViewController.h"

@interface MyCustomCollectionViewController ()

@end

@implementation MyCustomCollectionViewController

static NSString * const reuseIdentifier = @"cell";


-(id)initWithPins:(NSArray*)someArrayOfStuff {

    self = [super initWithNibName:@"MyCustomCollectionViewController" bundle:nil];

    if (self) {

        if (myArray) {
            myArray = [[NSMutableArray alloc] initWithArray:someArrayOfStuff];
        }


    }

    return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];

    [self.collectionView registerClass:[MyCustomCollectionViewCell class] forCellWithReuseIdentifier:reuseIdentifier];

    [self.collectionView reloadData];

}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}



#pragma mark <UICollectionViewDataSource>

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}


- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return myArray.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {


    MyCustomCollectionViewCell *cell = (MyCustomCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];


    MyCustomObject *obj = (MyCustomObject*)[myArray objectAtIndex:indexPath.row];
    [cell setObject:obj];


    return cell;

}

#pragma mark <UICollectionViewDelegateFlowLayout>

- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(UICollectionViewLayout *)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath {

    CGSize cellSize = CGSizeMake(self.view.frame.size.width/2, self.view.frame.size.width/2);

    return cellSize;
}

and here is my custom UICollectionViewCell

#import "MyCustomCollectionViewCell.h"


@implementation MyCustomCollectionViewCell
@synthesize theObject;
@synthesize mediaView;

- (void)awakeFromNib {

    mediaView = [[UIImageView alloc] initWithFrame:self.contentView.frame];
    mediaView.backgroundColor = self.backgroundColor;
    [self.contentView addSubview:mediaView];

}

-(id)initWithFrame:(CGRect)frame {

    NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"MyCustomCollectionViewCell" owner:nil options:nil];
    self = [topLevelObjects objectAtIndex:0];

    if (self) {

        self.frame = frame;


    }

    return self;

}

-(void)prepareForReuse {

    [mediaView setMediaWithObject:theObject];

}

-(void)setObject:(MyCustomObject*)obj {

    if (!theObject) {
        theObject = obj;
        [mediaView setMediaWithObject:obj];
    }

}

@end

I'm sure there is something obvious I am missing but can't figure out what. Thanks.

Answer 1

I think you have to implement the false condition of if (!theObject) { theObject = obj; [mediaView setMediaWithObject:obj]; } else { [mediaView setMediaWithObject:theObject] } in MyCustomCollectionViewCell.m

Good Luck

Answer 2

Try this :

-(void) prepareForReuse {

    [super prepareForReuse];
    [mediaView setMediaWithObject:nil];
}