Support for predictive back animations on Android

[xxfast]

Hi 👋 First of all - thank you for the awesome library!

Is there support for predictive back animations? Something like this

predictive-back-2.mp4

[mainrs]

As far as I can tell, navigation actions inside the app do not work with predictive back. However, when you're at the "root" of your app, predictive navigation works. I.e., the whole activity screen minimizes and shows that you return to your home screen.

Some useful resources on how it is implemented in the official navigation library:

• Commit
• NavHost relevant code

[kevinvanmierlo]

Okay I've been working on this for longer than I care to admit, but I am using this right now in my app (still in testing phase, but almost ready for release). The problem is that the animations in Jetpack compose do not support setting the progress manually (I think it's internal or private). So you'll have to do that all by yourself unfortunately. Inside the Transition files you can edit the transition to your liking.

The gist is here: https://gist.github.com/kevinvanmierlo/8e051c96c84de9f5c921912d28414038. There a quite a few files since I also added the swipe to go back for iOS (using Compose Multiplatform). If Android is all you care about you can skip the iOS part and just use the commonMain and androidMain and put them in your Android project.

Let me know what you think! The code could probably be better at a few places, but it took a while to get this working solid. So feedback is welcome.

[brueggenthies-adesso]

@kevinvanmierlo maybe the newly introduced SeekableTransitionState is something to look into?
Can be found here in the AndroidX source code.

The AndroidX Navigation library used this to integrate the predictive back gesture.

[kevinvanmierlo]

@brueggenthies-ams That's exactly what I needed when I created this! I was looking for this for the exact same reason to use it for predictive back gesture haha. They just created it a little too late.

Thanks for letting me know! I'll take a look at it soon and hopefully this will simplify the code.

[ivaniskandar]

If anyone is interested this is what I use right now. It's not perfect but still as simple as it gets while fulfilling my own requirements.

https://gist.github.com/ivaniskandar/af98c91d20a3124c6592bd7a830c0334

[akhbulatov]

@DevSrSouza are there plans to add gesture support on iOS?

[kevinvanmierlo]

@brueggenthies-ams I was just looking at the SeekableTransitionState, but it looks like there is a SeekableTransitionState in Compose Multiplatform, but it is a different version. Probably an earlier version unfortunately. If I look at what the SeekableTransitionState can do right now, it's much more difficult than the new version. So I think we'll need to wait a little longer for the version to be the same as Android right now. I think I have found the issue here: JetBrains/compose-multiplatform#4659. They're saying they will look at it after the 1.6.10 release (where we are now).

[zhimbura]

Any update here?

[ydhnwb]

👀