The completion block from play(fromMarker:toMarker) does not get called in the background.

[denandreychuk]

I have an animation with continuePlaying as the background behavior, and important login to be called when the animation finishes playing.

In my context, the app does not get suspended in the background due to an active audio session with the audio playback background mode enabled. However, for some reason, I receive the completion block only when entering the foreground.

[calda]

Are you using the SwiftUI LottieView?

I can reproduce this in the sample app in this repo. The SwiftUI view relies on the animation being present in the AnimationCacheProvider, which is implemented using an NSCache. When the app is backgrounded, iOS always clears the contents of NSCaches. We'll need to migrate this off of NSCache.

[denandreychuk]

No, I'm using UIKit for this particular API

[calda]

Ok, thanks for the info.

Could you please share a sample project that demonstrates this issue?

Alternatively, could you check locally if changing this line of code in CoreAnimationLayer.swift fixes the issue:

// Remove the progress animation once complete so we know when the animation
// has finished playing (if it doesn't loop infinitely)
timedProgressAnimation.isRemovedOnCompletion = true

to:

timedProgressAnimation.isRemovedOnCompletion = false

[denandreychuk]

I investigated this a bit more and found out that the problem was not in the completion block itself, but rather that a new animation cannot be started in the background, which ended up with the completion code also not getting fired.

So basically what I want to achieve is not to resync animation that looping with some logic by markers with the sound after entering foreground.

Sample project:
https://github.com/denandreychuk/lottie-background

[calda]

What happens if you try to use the main thready rendering engine rather than the core animation rendering engine, by updating the LottieConfiguration on your LottieAnimationView?

[denandreychuk]

If I use the Core Animation engine, then when I enter background with a currently running animation, it eventually completes with false, but on the main engine, the completion block is not called at all.

As for the ability to start a new animation in the background for the main engine, it's the same: not able to start.

[calda]

I'm going to convert this issue into a discussion, since it's not totally obvious if starting animations in the background should be supported