滚动时单元格显示不正确

我可以在收藏夹视图中选择图像。选择图像时，选择了错误的图像单元。一旦我向下滚动到该单元格之外，则不再选择该单元格。如何解决此问题？

imageView在情节提要中定义。资产在照片库中。

这是PhotoCell.h文件。

#import <UIKit/UIKit.h>
#import <AssetsLibrary/AssetsLibrary.h>

@interface PhotoCell : UICollectionViewCell

@property(nonatomic,strong) ALAsset * asset;
@property (nonatomic,weak) IBOutlet UIImageView * PhotoImageView;  

这是我的PhotoCell.m文件。

#import "PhotoCell.h"
@interface PhotoCell ()

@end

@implementation PhotoCell

#pragma mark - User Made Method 
- (void) setAsset:(ALAsset *)asset
{
    // 2
    _asset = asset;
    self.PhotoImageView.image = [UIImage imageWithCGImage:[asset thumbnail]];
}

#pragma mark - CollectionView Cell Method
-(void)prepareForReuse
{
}

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

PhotoCell *cell =(PhotoCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"PhotoCell" forIndexPath:indexPath];
ALAsset * asset = self.assets[indexPath.row];
cell.asset = asset;
cell.backgroundColor = [UIColor redColor];
}

#pragma mark - Collection View Delegate

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{

    //NSLog(@"%@ - %d", NSStringFromSelector(_cmd), indexPath.item);       
    PhotoCell *cell = (PhotoCell *)[collectionView cellForItemAtIndexPath:indexPath];
    chkboxBtn  = [UIButton buttonWithType:UIButtonTypeCustom];
    [chkboxBtn setFrame:CGRectMake(60, 60, 30, 30)];
    [chkboxBtn setTag:100];
    [chkboxBtn setImage:[UIImage imageNamed:@"success.png"] forState:UIControlStateNormal];
    [cell.contentView addSubview:chkboxBtn ];
}

-(void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath{

    // This removes the Check Box Button From the Cell After click it again
    PhotoCell *cell =(PhotoCell *)[collectionView cellForItemAtIndexPath:indexPath];
    [[cell.contentView viewWithTag:100] removeFromSuperview];

}