How to change UImage in UICollection UIImageView?

Question

I have a UICollectionView which contains a UIImageView and is only one row. I am trying to change the image to a selected image when tapped but the image will not update for some reason. The UIImage is set when the UICollectionView calls:

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

but it will not update when it calls:

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

Here is the code, as you can see I already tried setNeedsDisplay , reloadData, setImage and nullifying the UImageView itself, not setting it in the cellForItemAtIndexPath ... None of it has worked.

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

    UICollectionViewCell *cell;
    UIImage *curImage;

    static NSString *cellAvatarMediaIdentifier = @"cvAvatarCell";


    cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellAvatarMediaIdentifier forIndexPath:indexPath];

    Child *currentChild = [self.children objectAtIndex:indexPath.row];

    curImage = [UIImage imageNamed:@"male.png"];

    UIImageView *childSilhouetteView = (UIImageView *)[cell viewWithTag:300];

    if (curImage != nil)
    {
        // this WORKS !!!!
        [childSilhouetteView setImage:curImage];
    }

    return cell;
}

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

        Child *currentChild = [self.children objectAtIndex:indexPath.row];

        UIImageView *childSilhouetteView = (UIImageView *)[collectionView viewWithTag:300];

        selectedImage = [UIImage imageNamed:@"male_selected.png"];

        if (selectedImage != nil)
        {
                // This does NOT work, image is never updated
                NSLog(@"Before setting image");
                childSilhouetteView = nil;

                [childSilhouetteView setImage:selectedImage];
                [childSilhouetteView setNeedsDisplay];
                [collectionView reloadData];
        }
}

EDUsta EDUsta · Accepted Answer · 2017-05-07T20:43:04

You also need to find the corresponding child in didSelectItemAtIndexPath:, currently you're accessing the collectionView's view with tag.

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

        Child *currentChild = [self.children objectAtIndex:indexPath.row];

        UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];

        UIImageView *childSilhouetteView = (UIImageView *)[cell viewWithTag:300];

        selectedImage = [UIImage imageNamed:@"male_selected.png"];

        if (selectedImage != nil)
        {
                // This does NOT work, image is never updated
                NSLog(@"Before setting image");
              //  childSilhouetteView = nil;

                [childSilhouetteView setImage:selectedImage];
                [childSilhouetteView setNeedsDisplay];
               // [collectionView reloadData];
        }
}

If you call reloadData, your collectionView will be redrawn so you will see the default images on your views.

How to change UImage in UICollection UIImageView?

2 Answers