uicollection view reusable cell images are reloading while scrolling

Question

hello am using UICollectionView for showing images in my iphone application but when i scrolling the view the loaded images are gone and loading images again this is because of "dequeueReusableCellWithReuseIdentifier" and this is my code

static NSString * const kCellReuseIdentifier = @"collectionViewCell";
[self.collectionViewPack registerNib:[UINib nibWithNibName:@"CollectionViewItem" bundle:nil] forCellWithReuseIdentifier:kCellReuseIdentifier];

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

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

        cell.layer.shouldRasterize = YES;
        cell.layer.rasterizationScale = [UIScreen mainScreen].scale;

        UILabel *titleLabel = (UILabel *)[cell viewWithTag:100];
        UIImageView *icon=(UIImageView *)[cell viewWithTag:101];
        //    [titleLabel setText:[NSString stringWithFormat:@"%d",indexPath.row]];
        [titleLabel setText:[NSString stringWithFormat:@"%@",[arrayImages objectAtIndex:indexPath.row]]];
        icon.image =[UIImage imageNamed:@"loading-1.png"];


        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            NSString *imagePath = [NSString stringWithFormat:@"%@", [test.arrImages objectAtIndex:indexPath.row]];
            NSURL *imageUrl     = [NSURL URLWithString:imagePath];
            NSData *imageData   = [NSData dataWithContentsOfURL:imageUrl];
            UIImage *image      = nil;
            if (imageData){

                image = [[UIImage alloc] initWithData:imageData];
                icon.image = image;

            }

            [image release];

        });



        return cell;


    }

please help me out from this.

Check [this answer](http://stackoverflow.com/a/9188019/1407017). It is for `UITableViewCell` lazy loading images but same can be applied for `UICollectionViewCell`. — Amar, Sep 12 '13 at 13:50

score 3 · Accepted Answer · answered Sep 12 '13 at 14:47

3

I guess you need to add some image cache to your code, I recommend you to use AFNetworking, you can easily do:

import "UIImageView+AFNetworking.h"

......

[cell.imageView setImageWithURL:imageUrl placeholderImage:[UIImage imageNamed:@"default"]];

And, it has an internal Cache that will help :D

and for your code... try by adding this in your block

dispatch_async(dispatch_get_main_queue(), ^{
    icon.image = image;
});

answered Sep 12 '13 at 14:47

Camo

1,778
14
12

You should really avoid using `dispatch_async` to fix issues in your code unless you're dealing with an Apple bug. Generally, this introduces technical debt and unnecessary complexity. – Zorayr Jan 06 '15 at 05:28

score 0 · Answer 2 · edited Mar 06 '14 at 18:08

0

change kCellReuseIdentifier to dynamic

static NSString * const kCellReuseIdentifier = @"collectionViewCell";

to

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

    NSString * kCellReuseIdentifier = 
      [NSString stringWithFormat:@"collectionViewCell%d",indexPath.row];

It may work

edited Mar 06 '14 at 18:08

Alex Cio

6,014
5
44
74

answered Sep 12 '13 at 13:37

sabeer

603
10
28

Abdullah Alhattami · Answer 3 · 2014-09-15T10:26:37.250

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

    // Setup cell identifier
    static NSString *cellIdentifier = @"put you viewController here";

    /* this block to use nib-based cells */
     UICollectionViewCell *cell = 
      [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier 
                                                  forIndexPath:indexPath];
    /* end of nib-based cell block */

    /* this block to use subclass-based cells */
  yourviewController *cell = 
  (CVCell *)[collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier 
                                                      forIndexPath:indexPath];

uicollection view reusable cell images are reloading while scrolling

3 Answers3