How to display video from ALAsset to UICollectionview ios - ios

Question

I tried below code to get all videos from photo library by using ALAsset. For now, i want to display all videos to a UICollectionview but it doesn't seem to display anything. Please give me some advice. Thanks in advance.
-ViewDidLoad() : get all videos from Photo Library
allVideos = [[NSMutableArray alloc] init];
ALAssetsLibrary *assetLibrary = [[ALAssetsLibrary alloc] init];
[assetLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop)
{
if (group)
{
[group setAssetsFilter:[ALAssetsFilter allVideos]];
[group enumerateAssetsUsingBlock:^(ALAsset *asset, NSUInteger index, BOOL *stop)
{
if (asset)
{
dic = [[NSMutableDictionary alloc] init];
ALAssetRepresentation *defaultRepresentation = [asset defaultRepresentation];
NSString *uti = [defaultRepresentation UTI];
NSURL *videoURL = [[asset valueForProperty:ALAssetPropertyURLs] valueForKey:uti];
NSString *title = [NSString stringWithFormat:#"video %d", arc4random()%100];
UIImage *image = [self imageFromVideoURL:videoURL];
[dic setValue:image forKey:#"image"];
[dic setValue:title forKey:#"name"];
[dic setValue:videoURL forKey:#"url"];
[allVideos addObject:dic];
[_collectionView reloadData];
}
}];
}
}
failureBlock:^(NSError *error)
{
NSLog(#"error enumerating AssetLibrary groups %#\n", error);
}];
-imageFromVideoURL():
- (UIImage *)imageFromVideoURL:(NSURL*)videoURL
{
// result
UIImage *image = nil;
// AVAssetImageGenerator
AVAsset *asset = [[AVURLAsset alloc] initWithURL:videoURL options:nil];;
AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
imageGenerator.appliesPreferredTrackTransform = YES;
// calc midpoint time of video
Float64 durationSeconds = CMTimeGetSeconds([asset duration]);
CMTime midpoint = CMTimeMakeWithSeconds(durationSeconds/2.0, 600);
// get the image from
NSError *error = nil;
CMTime actualTime;
CGImageRef halfWayImage = [imageGenerator copyCGImageAtTime:midpoint actualTime:&actualTime error:&error];
if (halfWayImage != NULL)
{
// CGImage to UIImage
image = [[UIImage alloc] initWithCGImage:halfWayImage];
[dic setValue:image forKey:#"name"];
NSLog(#"Values of dictionary==>%#", dic);
NSLog(#"Videos Are:%#",videoURL);
CGImageRelease(halfWayImage);
}
return image;
}
Start to display all thumbnails of video to UICollectionView:
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return allVideos.count;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
NSLog(#"allvideo %#", allVideos);
ALAsset *alasset = [allVideos objectAtIndex:indexPath.row];
return cell;
}

Answer 1

Replace this Line:-
[allVideos addObject:dic];
With
[allVideos addObject: asset];
And in this method:-
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell=[collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
NSLog(#"allvideo %#", allVideos);
ALAsset *alasset = [allVideos objectAtIndex:indexPath.row];
yourImageView.image = [UIImage imageWithCGImage:alasset.thumbnail];
}

Answer 2

First of all take the code [_collectionView reloadData] out of the ALAssetsGroupEnumerationResultsBlock (the block you passed to -enumerateAssetsUsingBlock:) as it'll call the -reloadData for all the AVAssets found.
There is a sample app "MyImagePicker" available from apple which does the exact thing you want to do. You can study the working from there.