Instances of UICollectionViewCell showing behind other instances of UICollectionView - ios

Question

To preface, I have some experience with iOS development, but this is my first app that I am going to publish to the AppStore, and also my first experience utilizing UICollectionView.
Here is a summary of what I am doing in my app:
I have a paged UICollectionView which contains several fullscreen UICollectionViewCells. Within each of these cells is another UICollectionView ('subCollectionView'), containing UICollectionViewCells ('subCollectionViewCells') which currently have their label set to "Test Text". When scrolling to the second collectionViewCell, the subCollectionViewCells of the first collectionViewCell are visible behind the second collectionViewCell's subCollectionView. I have linked the images to what is happening here.
The CollectionViewCell that includes the subCollectionView:
[VLCategoryCollectionViewCell.h]
#import <UIKit/UIKit.h>
#interface VLCategoryCollectionViewCell : UICollectionViewCell
#property (nonatomic, strong) NSString *imageName;
#property (strong, nonatomic) IBOutlet UIView *moduleSubview;
- (void)updateCell;
#end
[VLCategoryCollectionViewCell.m]
#import "VLCategoryCollectionViewCell.h"
#import "VLModuleViewController.h"
#interface VLCategoryCollectionViewCell()
#property (strong, nonatomic) IBOutlet UIImageView *imageView;
#property (strong, nonatomic) IBOutlet UILabel *categoryName;
#property (strong, nonatomic) VLModuleViewController *moduleViewController;
#end
#implementation VLCategoryCollectionViewCell
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
NSArray *arrayOfViews = [[NSBundle mainBundle]
loadNibNamed:#"VLCategoryCollectionViewCell" owner:self options:nil];
if ([arrayOfViews count] < 1) {
return nil;
}
if (![[arrayOfViews objectAtIndex:0] isKindOfClass:[UICollectionViewCell class]]) {
return nil;
}
self = [arrayOfViews objectAtIndex:0];
}
return self;
}
-(void)updateCell {
_moduleViewController = [[VLModuleViewController alloc] initWithNibName:#"VLModuleViewController" bundle:nil];
_moduleViewController.view.frame = self.moduleSubview.bounds;
[self.moduleSubview addSubview:_moduleViewController.view];
NSString *sourcePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"Assets"];
NSString *filename = [NSString stringWithFormat:#"%#/%#", sourcePath, self.imageName];
UIImage *image = [UIImage imageWithContentsOfFile:filename];
NSString *fileTitle = [[filename lastPathComponent] stringByDeletingPathExtension];
[self.categoryName setFont:[UIFont fontWithName:#"OpenSans-ExtraBold" size:72.0]];
[self.categoryName setText:fileTitle];
[self.imageView setImage:image];
[self.imageView setContentMode:UIViewContentModeScaleAspectFit];
}
#end
[VLModuleViewController.h]
#import <UIKit/UIKit.h>
#interface VLModuleViewController : UIViewController <UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout>
#end
[VLModuleViewController.m]
#import "VLModuleViewController.h"
#import "VLModuleCollectionViewCell.h"
#interface VLModuleViewController ()
#property (nonatomic, strong) IBOutlet UICollectionView *moduleView;
#property (nonatomic, strong) NSArray *moduleArray;
#property (nonatomic) int currentIndex;
#property (nonatomic) NSString *cellIdentifier;
#end
#implementation VLModuleViewController
- (void)loadView {
[super loadView];
NSArray *moduleArray = [[NSBundle mainBundle] pathsForResourcesOfType:#"png" inDirectory:#"Module_Tests"];
NSMutableArray *moduleImageArray = [[NSMutableArray alloc] initWithCapacity:[moduleArray count]];
for (NSString *path in moduleArray) {
[moduleImageArray addObject:[UIImage imageWithContentsOfFile:path]];
}
self.moduleArray = [NSArray arrayWithArray:moduleArray];
}
- (void)viewDidLoad {
[super viewDidLoad];
[self setupCollectionView];
UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
[flowLayout setScrollDirection:UICollectionViewScrollDirectionHorizontal];
[self.moduleView setPagingEnabled:YES];
[self.moduleView setCollectionViewLayout:flowLayout];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
#pragma mark -
#pragma mark UICollectionView methods
- (void)setupCollectionView {
[self.moduleView registerClass:[VLModuleCollectionViewCell class] forCellWithReuseIdentifier:#"VLModuleCollectionViewCell"];
UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
[flowLayout setScrollDirection:UICollectionViewScrollDirectionHorizontal];
[self.moduleView setCollectionViewLayout:flowLayout];
}
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return [self.moduleArray count];
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
VLModuleCollectionViewCell *cell = (VLModuleCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:#"VLModuleCollectionViewCell" forIndexPath:indexPath];
cell.titleLabel.text = #"Module Title Goes Here";
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return CGSizeMake(235, 147);
}
#end

Answer 1

I had a similar issue with labels overwriting themselves in collectionView, try calling your updateCell method in awakeFromNib, this did the trick for me.