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POUICollectionViewCell subclass containing UIImageView outlet not displaying image
 

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  1. POUICollectionViewCell subclass containing UIImageView outlet not displaying image
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    <p>I have a <code>UICollectionViewCell</code> subclass called <code>AlbumCVC</code> that contains a single <code>IBOutlet</code> --- a <code>UIImageView</code> called <code>cellView</code>. I'm setting the value of <code>cellView</code> for each cell inside the following method:</p> <pre><code>- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{ UICollectionViewCell *cell; cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"albumPhotoCell" forIndexPath:indexPath]; cell.backgroundColor = [UIColor blueColor]; if ([cell isKindOfClass:[AlbumCVC class]]){ AlbumCVC *albumCVC = (AlbumCVC *)cell; ALAsset *thisImage = [self.albumPhotos objectAtIndex:indexPath.item]; albumCVC.imageView.frame = albumCVC.contentView.frame; albumCVC.contentView.contentMode = UIViewContentModeScaleAspectFit; albumCVC.imageView.image = [UIImage imageWithCGImage:[thisImage aspectRatioThumbnail]]; } } return cell; } </code></pre> <p>where <code>albumPhotos</code> is an NSMutableArray of <code>ALAsset</code>s. I'm sure that the property is getting set correctly because I get sensible results when I log the <code>albumCVC.cellImage.image.bounds.size</code>. Cells are also sized properly as the frames are visible when I set the background color. But for some reason, <code>cellImage</code> won't display. Is there another method call I need to make inside <code>collectionView:cellForItemAtIndexPath:</code> in order to get the image to show up?</p> <p><strong>Update:</strong> On the advice of a very smart friend, I tried moving the <code>UIImageView</code> out of the cell, putting it elsewhere in the main view, and everything worked lovely. The problem appears to have something to do with the frame / bounds of the <code>UIImageView</code>. I think there's a method call I need to make so that the cell's subview expands to fit the newly-resized cell following the call to <code>collectionView:layout:sizeForItemAtIndexPath:</code>. The problem now is that <code>UIImageView.image.size</code> is a read-only property, so I can't resize it directly.</p> <p><strong>Update 2:</strong> On another piece of advice I looked at the frame and bounds of the cell's <code>contentView</code> and <code>cellImage</code> and found that they weren't matching up. Added another method call to make them equal, and even changed <code>contentMode</code> to <code>UIViewContentModeScaleAspectFit</code> in order to try and get the cell to render the thumbnail properly. Unfortunately, I'm still getting tiny thumbnails inside huge cells. Any idea why? Updated code above and below.</p> <p>For the sake of completeness, here's the entire class implementation:</p> <pre><code>#import "AlbumViewController.h" #import "AlbumCVC.h" #import &lt;AssetsLibrary/AssetsLibrary.h&gt; @interface AlbumViewController () @end @implementation AlbumViewController #pragma constants const int IPHONE_WIDTH = 320; #pragma delegate methods - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{ // Get the count of photos in album at index albumIndex in the PhotoHandler NSInteger numCells = [self.group numberOfAssets]; return numCells; } - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{ UICollectionViewCell *cell; cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"albumPhotoCell" forIndexPath:indexPath]; cell.backgroundColor = [UIColor blueColor]; if ([cell isKindOfClass:[AlbumCVC class]]){ AlbumCVC *albumCVC = (AlbumCVC *)cell; ALAsset *thisImage = [self.albumPhotos objectAtIndex:indexPath.item]; } albumCVC.imageView.frame = albumCVC.contentView.frame; albumCVC.contentView.contentMode = UIViewContentModeScaleAspectFit; albumCVC.imageView.image = [UIImage imageWithCGImage:[thisImage aspectRatioThumbnail]]; } return cell; } - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{ //Copy a pointer to an asset from the album ALAsset *thisImage = [self.albumPhotos objectAtIndex:indexPath.item]; //Zen - are you sure thisImage represents a valid image? //Copy that asset's size and create a new size struct CGSize thisSize = thisImage.defaultRepresentation.dimensions; CGSize returnSize; // force all previews to be full width returnSize.width = IPHONE_WIDTH; returnSize.height = IPHONE_WIDTH * thisSize.height / thisSize.width; return returnSize; } #pragma lifecycle methods - (void)viewWillAppear:(BOOL)animated{ [self.albumPhotos removeAllObjects]; //"handler" is a class that manages calls to the ALAssetLibrary. self.albumIndex is an integer that gets set on segue. As far as I can tell, everything in the below method is working fine --- cells are sized properly. self.group = self.albumDelegate.handler.groups[self.albumIndex]; [self.group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) { if (result) { NSLog(@"Just added an object to albumPhotos."); [self.albumPhotos addObject:result]; NSLog(@"The item in albumPhotos is class %@", [self.albumPhotos[0] class]); } }]; } #pragma instantiation - (ALAssetsGroup *)group{ if (!_group) { _group = [[ALAssetsGroup alloc]init]; } return _group; } - (NSMutableArray *)albumPhotos{ if (!_albumPhotos) { _albumPhotos = [[NSMutableArray alloc]init]; } return _albumPhotos; } @end </code></pre> <p><strong>Update 3:</strong> I can't be certain what the problem was initially, but I know that it now works with the following <code>cellForItem</code> implementation:</p> <pre><code>- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{ UICollectionViewCell *cell; cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"albumPhotoCell" forIndexPath:indexPath]; if ([cell isKindOfClass:[AlbumCVC class]]) { AlbumCVC *albumCVC = (AlbumCVC *)cell; albumCVC.albumImageView.image = [[UIImage alloc] initWithCGImage:[self.albumAssets[[self reverseAlbumIndexForIndex:indexPath.item]] thumbnail]]; } cell.alpha = [self alphaForSelected:self.selectedItems[@(indexPath.item)]]; return cell; } </code></pre> <p>There's no screwing around with frames or bounds anywhere, everything just works. Maybe it's the difference between <code>[[UIImage alloc]initWithCGImage]</code> and <code>[UIImage imageWithCGImage]</code>?</p>
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    1. USjefflovejapan
    1. USjefflovejapan
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    1. CODo you use storyboard?How can you register cell?
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      1. POUICollectionViewCell subclass containing UIImageView outlet not displaying image
      1. USLE SANG
    2. COYeah, I use a storyboard. The cell is registered `albumPhotoCell`.
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      1. POUICollectionViewCell subclass containing UIImageView outlet not displaying image
      1. USjefflovejapan
    3. COHave you checked that the execution goes into the `if ([cell isKindOfClass:[AlbumCVC class]]){ ... }` block? - Have you checked that `albumCVC.cellImage` is not `nil`?
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      1. POUICollectionViewCell subclass containing UIImageView outlet not displaying image
      1. USMartin R
 

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