Reused cells in a UICollectionView show multiple UIImageViews when they should only show one

Question

Im having a problem with my UICollectionView. Initially it displays fine, showing a grid of cells, each cell with a single UIImageView. These

Answer 1

for (UIView *prevSubview in cell.contentView.subviews) {
    [prevSubview removeFromSuperview];
}

Answer 2

This is for removing duplicate text from label in uicollectionviewcell.

// Viewdidload
[_collectionView registerClass:[UICollectionviewcell class]     forCellWithReuseIdentifier:@"cellIdentifier"];



//in this method create label like this
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
  {
     UICollectionViewCell *cell=[collectionView   dequeueReusableCellWithReuseIdentifier:@"cellidentifier" forIndexPath:indexPath];
     for (UILabel *lbl in cell.contentView.subviews)
        {
            if ([lbl isKindOfClass:[UILabel class]])
            {
                [lbl removeFromSuperview];
            }
        }
     UILabel *nameLbl=[[UILabel alloc] initWithFrame:CGRectMake(0, 10, 50, 20)];
     nameLbl.text=[Array objectAtIndex:indexpath.row];                                                                                                                                  
     nameLbl.textColor=[UIColor whiteColor];
     [cell.contentView addSubview:nameLbl];
     return cell;

   }

Answer 3

Right after

UICollectionViewCell * cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];

Just add this line,

[[[cell contentView] subviews] makeObjectsPerformSelector:@selector(removeFromSuperview)];

Answer 4

The problem is that you keep adding views to the UICollectionViewCell as they are being reused automagically by the UICollectionView. So the old UIImageView's are still on the cell as you are adding one more as the cellForItemAtIndexPath: is called.

DO NOT USE addSubview:!

Instead you could make a custom cell with all the views you want already in them. So that when the cellForItemAtIndexPath: is called you only need to set the contents of this CustomCollectionViewCell instead.

This way it will certainly stop being corrupted.

---

How to build a CustomCell.

Step1: Create the .h & .m class.

CustomCell.h

#import <UIKit/UIKit.h>

@interface CustomCell : UICollectionViewCell
{
    UIImageView *imageView;
}

@property (nonatomic, retain) UIImageView *imageView; //this imageview is the only thing we need right now.

@end

CustomCell.m

#import "CustomCell.h"

@implementation CustomCell

@synthesize imageView;

- (id)initWithFrame:(CGRect)aRect
{
    if (self = [super initWithFrame:aRect])
    {
         //we create the UIImageView in this overwritten init so that we always have it at hand.
         imageView = [UIImageView alloc] init];
         //set specs and special wants for the imageView here.
         [self addSubview:imageView]; //the only place we want to do this addSubview: is here!

         //You wanted the imageView to react to touches and gestures. We can do that here too.
         UITapGestureRecognizer * tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onButtonTapped:)];
        [tap setNumberOfTapsRequired:1];
        [self addGestureRecognizer:tap];


        //We can also prepare views with additional contents here!
        //just add more labels/views/whatever you want.
    }
    return self;
}

-(void)onButtonTapped:(id)sender
{
    //the response to the gesture.
    //mind that this is done in the cell. If you don't want things to happen from this cell.
    //then you can still activate this the way you did in your question.

}

Step2: Import it! Now that we created the CustomCell we can import it in the class we want to use it in.

Step3: Use it in action!

// creates the individual cells to go in the menu view
- (CustomCell*) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

    // create collection view cell
    CustomCell *cell = (CustomCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"CustomCell" forIndexPath:indexPath]; //this is the place where the CustomCell does his magic.
    //Make sure to use the CustomCellReuseId that you register in the viewdidload/loadview (step4)

    // add a button image
    NSString * buttonPath=[[NSBundle mainBundle] pathForResource:@"button" ofType:@"png" inDirectory:[[buttons objectAtIndex:indexPath.row] objectForKey:@"name"]];

    cell.imageView.image = [UIImage imageWithContentsOfFile:buttonPath]; //place the image on the CustemCell.imageView as we prepared.

    // set tag to the indexPath.row so we can access it later
    [cell setTag:indexPath.row]; //we don't need this to access the cell but I left this in for your personal want.

/*
 * we can now do this from the CustomCell as well!
 *
    // add interactivity
    UITapGestureRecognizer * tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onButtonTapped:)];
    [tap setNumberOfTapsRequired:1];
    [cell addGestureRecognizer:tap];
*/
    // return the cell
    return cell;

}

Step4: Register the cell to the collectionView

in the viewDidLoad / loadView add this line:

[_collectionView registerClass:[CustomCell class] forCellWithReuseIdentifier:@"CustomCell"];

Step5: Enjoy! Your CustomCell is done. Now do whatever you like and don't forget to get some coffee too.

Answer 5

For those who are looking for a Swifty answer, add this function to your CustomCell class:

override func prepareForReuse() {
    contentView.subviews.forEach({ $0.removeFromSuperview() })
    // replace contentView with the superview of the repeating content.
}

Answer 6

For anyone who is adding UICollectionView programmatically and have a custom cell, in other words no XIB file, then you have to add this line to viewDidLoad

[_collectionView registerClass:[CustomCell class] forCellWithReuseIdentifier:@"cellIdentifier"];