I was working on a project that shows videos from the Photo Library. However, each time I replaced the current video, the VideoPlayer turned black screen for a while.

I had no idea why this happened so I looked for what Photos app did for videos. It turned out that Photos showed a preview of the video first and then automatically played the video when the video data was loaded.

I did the same. First I fetched the preview image. When the preview was downloaded, I fetched the video.

The issue was the same. After some investigation, I found that the method of fetching video was called twice, which was not expected. Then I found that was because fetching preview may be called multiple times. Photo Library may provide a low quality image first then provide the full quality image. This issue was solved by read the info dictionary of the fetching preview result. But the black screen issue was still there.

Maybe the AVPlayer or PlayerItem was not ready?

if let video {
    player.replaceCurrentItem(with: video)
    
    Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { timer in
        if player.status == .readyToPlay {
            playerItem = video
            timer.invalidate()
        }
    }
}

The result was the same.

Maybe there was still some time between the player was ready and the player was really playing.

if let video {
    player.replaceCurrentItem(with: video)
    
    Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { timer in
        if player.status == .readyToPlay {
            player.play()
            
            if player.timeControlStatus == .playing {
                playerItem = video
                timer.invalidate()
            }
        }
    }
}

The issue solved.

Conclusion

1. Do not create another AVPlayer each time. Just create an empty player and replace the replaceCurrentItem.
2. There was time gap between player ready and player real playing. So you need to play the player first when player was ready and then updated the UI after the player was really playing.
3. I was using a timer instead of a notification as the former was more simple to use.