dotLottie support

[lennartstolz]

Hey all!

I personally think built-in .lottie support for airbnb/lottie-ios would be beneficial and could make working with Lottie animations even easier.

Motivation

.lottie are a great addition to working with Lottie and I'd love to see the lottie-ios project being able to open them.
I'm citing the key benefits mentioned at dotlottie.io:

Establishing an identity

[...] changing the file extension from .json to .lottie avoids confusion and brings a lot of ease for designers and developers dealing with Lottie animations regularly.

Archiving

Storing, distributing and consuming a Lottie with its dependent assets is challenging for designers and developers, in terms of storing them on file systems and integrating into apps and websites.

Compression

[...] The use of archiving with compression allows all the assets required by an animation to be grouped together and the total file size to be dramatically reduced.

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Additional Information

• The airbnb/lottie-android library already does support .lottie files.

• There is no high-level built-in Swift/iOS/macOS framework to unpack the dotLottie ZIP archive.

  • We could make use of some of the great community ZIP frameworks:
    • ZIP by marmelroy - based on minizip
    • ZIPFoundation by weichsel built on top of Apples Compression framework
  • As the animation player would only need a fraction of the functionality those frameworks are providing and lottie-ios currently have no external dependencies, it could also be an option to implement the unzipping of the archives with Compression (which is available on macOS, iOS, tvOS, watchOS)

🙇 Looking forward to your replies!

[calda]

It would be great for this repo to support .lottie files by default. Definitely interested in having this functionality available.

One of the first hurdles, as you mentioned, is finding a way to unzip these files. I like the look of the ZIPFoundation project in particular, since it is built on top of Apple's Compression framework.

Lottie currently doesn't include any third-party dependencies though, and I'm not sure how feasible it is to add one. I expect this will be easy for Swift Package Manager. I'm not sure how this works for Cocoapods though, and I think it may be difficult or impossible to do this for Carthage. I think a good first step here would be attempting to integrate ZIPFoundation into the repo and make sure that SPM, Cocoapods, and Carthage all still work correctly.

[rasberik]

Thank you for adding built in.lottie support.
I'd like to try to use it as soon as it will be released in next version as it helps to drastically reduce the bundle resources, but currently there is an issue that might result on missing animation for locally loaded .lottie view.

Any ideas on best approaches on how to handle it, desirably with least (or none) code change on view lifecycle after switching from .json to .lottie?

The PR above would be somewhat acceptable for my use case, at least as temporary workaround, but would nice to hear opinions on this.