How to reuse UICollectionViewCell with nested UIView for video - ios

Question

I am using a UICollectionViewController to display cells with content loaded from an external JSON api. To be specific, these cells include UILabels for the user that posted the video, the title of the video, etc.
In addition to the text labels, there is a large UIView in the middle of the cell to play video.
The following is the code for my UICollectionViewCell.
class PostCell : UICollectionViewCell {
var videoCell: VideoPlayerView
let storyTitleLabel: UILabel = {
let storyTitleLabel = UILabel()
storyTitleLabel.translatesAutoresizingMaskIntoConstraints = false
return storyTitleLabel
}()
let usernameLabel: UILabel = {
let usernameLabel = UILabel()
usernameLabel.translatesAutoresizingMaskIntoConstraints = false
return usernameLabel
}()
func prepare(post: ApiPost) {
self.usernameLabel.text = post.user?.username
self.postTitleLabel.text = post.title!
self.storyTitleLabel.text = post.story?.title
self.videoCell.prepare(post: post)
}
func focus() {
self.videoCell.focus()
}
func unfocus() {
self.videoCell.unfocus()
}
}
When a user is scrolling through the UICollectionView and the middle of the screen is over the visible UICollectionViewCell, the focus method is called.
This loads up the video corresponding to the ApiPost (api data wrapper) for that UICollectionViewCell.
I have also programmed my own subclass of UIView for the videoCell as you can see. The following is the source code of that class.
class VideoPlayerView: UIView {
func prepare(post: ApiPost) {
self.post = post
self.videoUrl = sharedConfig.apiUrl + "/stream/" + post.video!.uuid! + ".mp4"
if let url = URL(string: self.videoUrl!) {
let avPlayerItem = AVPlayerItem(url: url)
if (self.hasReceivedApiData) {
DispatchQueue.global(qos: .background).async {
print("inserting...")
self.player?.replaceCurrentItem(with: avPlayerItem)
print("done")
}
} else {
self.hasReceivedApiData = true
self.player = AVQueuePlayer.init()
self.player?.automaticallyWaitsToMinimizeStalling = false
self.player?.insert(avPlayerItem, after: nil)
self.player?.volume = 1
let playerLayer = AVPlayerLayer(player: self.player)
playerLayer.frame = CGRect(x: 0, y: -70, width: self.frame.width - 32, height: self.frame.height)
self.layer.addSublayer(playerLayer)
}
NotificationCenter.default.addObserver(forName: .AVPlayerItemDidPlayToEndTime, object: self.player?.currentItem, queue: nil, using: { (_) in
DispatchQueue.main.async {
self.player?.seek(to: kCMTimeZero)
self.player?.play()
}
})
}
}
func focus() {
self.player?.volume = 1.0
self.player?.play()
}
func unfocus() {
self.player?.seek(to: kCMTimeZero)
self.player?.pause()
}
}
The problem that I am having is that when I scroll over the UICollectionView, it lags really badly when prepare() is called on a reused UICollectionViewCell. It seems that calling self.player?.replaceCurrentItem(with: avPlayerItem) is slowing the UI down on scroll. I have verified this by putting the print calls between. It seems this is a slow operation that is lagging the UI, as you can see, I even tried putting that operation on a different thread, but no luck.
Am I displaying video properly in a UICollectionViewCell? Should I be doing this using some other method? The only way I could figure out to clear the old video is by using an AVQueuePlayer to clear out old AVPlayerItems, and insert the new AVPlayerItem when the cell is reused and prepared for the next video.
Any help on this would be greatly appreciated! Thanks in advance.