这是一个关于在UICollectionView中显示“视频墙”的工作解决方案：
1）将所有单元格存储在NSMapTable中（从此以后，您只能从NSMapTable访问单元格对象）：
self.cellCache = [[NSMapTable alloc] initWithKeyOptions:NSPointerFunctionsWeakMemory valueOptions:NSPointerFunctionsStrongMemory capacity:AppDelegate.sharedAppDelegate.assetsFetchResults.count];
for (NSInteger i = 0; i < AppDelegate.sharedAppDelegate.assetsFetchResults.count; i++) {
[self.cellCache setObject:(AssetPickerCollectionViewCell *)[self.collectionView dequeueReusableCellWithReuseIdentifier:CellReuseIdentifier forIndexPath:[NSIndexPath indexPathForItem:i inSection:0]] forKey:[NSIndexPath indexPathForItem:i inSection:0]];
}
2) 将此方法添加到您的UICollectionViewCell子类中：
- (void)setupPlayer:(PHAsset *)phAsset {
typedef void (^player) (void);
player play = ^{
NSString __autoreleasing *serialDispatchCellQueueDescription = ([NSString stringWithFormat:@"%@ serial cell queue", self]);
dispatch_queue_t __autoreleasing serialDispatchCellQueue = dispatch_queue_create([serialDispatchCellQueueDescription UTF8String], DISPATCH_QUEUE_SERIAL);
dispatch_async(serialDispatchCellQueue, ^{
__weak typeof(self) weakSelf = self;
__weak typeof(PHAsset) *weakPhAsset = phAsset;
[[PHImageManager defaultManager] requestPlayerItemForVideo:weakPhAsset options:nil
resultHandler:^(AVPlayerItem * _Nullable playerItem, NSDictionary * _Nullable info) {
if(![[info objectForKey:PHImageResultIsInCloudKey] boolValue]) {
AVPlayer __autoreleasing *player = [AVPlayer playerWithPlayerItem:playerItem];
__block typeof(AVPlayerLayer) *weakPlayerLayer = [AVPlayerLayer playerLayerWithPlayer:player];
[weakPlayerLayer setFrame:weakSelf.contentView.bounds];
[weakPlayerLayer setVideoGravity:AVLayerVideoGravityResizeAspect];
[weakPlayerLayer setBorderWidth:0.25f];
[weakPlayerLayer setBorderColor:[UIColor whiteColor].CGColor];
[player play];
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf.contentView.layer addSublayer:weakPlayerLayer];
});
}
}];
});
}; play();
}
3) 从你的UICollectionView代理中以这种方式调用上述方法：
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
if ([[self.cellCache objectForKey:indexPath] isKindOfClass:[AssetPickerCollectionViewCell class]])
[self.cellCache setObject:(AssetPickerCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:CellReuseIdentifier forIndexPath:indexPath] forKey:indexPath];
dispatch_async(dispatch_get_global_queue(0, DISPATCH_QUEUE_PRIORITY_HIGH), ^{
NSInvocationOperation *invOp = [[NSInvocationOperation alloc]
initWithTarget:(AssetPickerCollectionViewCell *)[self.cellCache objectForKey:indexPath]
selector:@selector(setupPlayer:) object:AppDelegate.sharedAppDelegate.assetsFetchResults[indexPath.item]];
[[NSOperationQueue mainQueue] addOperation:invOp];
});
return (AssetPickerCollectionViewCell *)[self.cellCache objectForKey:indexPath];
}
顺便说一下，以下是如何使用PHFetchResult集合填充Photos应用程序中视频文件夹中的所有视频：
- (PHFetchResult *)assetsFetchResults {
__block PHFetchResult *i = self->_assetsFetchResults;
if (!i) {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
PHFetchResult *smartAlbums = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeSmartAlbum subtype:PHAssetCollectionSubtypeSmartAlbumVideos options:nil];
PHAssetCollection *collection = smartAlbums.firstObject;
if (![collection isKindOfClass:[PHAssetCollection class]]) collection = nil;
PHFetchOptions *allPhotosOptions = [[PHFetchOptions alloc] init];
allPhotosOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
i = [PHAsset fetchAssetsInAssetCollection:collection options:allPhotosOptions];
self->_assetsFetchResults = i;
});
}
NSLog(@"assetsFetchResults (%ld)", self->_assetsFetchResults.count);
return i;
}
如果您想要过滤本地视频（而不是iCloud中的视频），这是我假设的，因为您正在寻找平滑滚动：
- (NSArray *)phAssets {
NSMutableArray *assets = [NSMutableArray arrayWithCapacity:self.assetsFetchResults.count];
[[self assetsFetchResults] enumerateObjectsUsingBlock:^(PHAsset *asset, NSUInteger idx, BOOL *stop) {
if (asset.sourceType == PHAssetSourceTypeUserLibrary)
[assets addObject:asset];
}];
return [NSArray arrayWithArray:(NSArray *)assets];
}
AVPlayer没有性能解决方案。正如我在我的编辑部分所述，性能问题固有于AVFoundation的实现中，你无法对此做任何事情。如果你想在某种滚动视图中播放视频，并且不想丢失大量帧，则唯一真正的方法是从头开始构建自己的视频播放器，完全绕过AVPlayer。或者，你可以等待iOS 10并希望苹果公司到那时已经解决了这个问题。 - AntonioAVPlayerLayer有很多内部设置，在可能可见之前不会发生；也就是说，它必须存在于窗口内，即使只是一个运行循环。通过这样做，我们在快速添加/删除播放器时几乎没有主线程阻塞。 - CIFilter