[Idea] [Navigation Animation] Animations between destinations with and without Scaffold

In general, it is advised to only use a single (Animated)NavHost. However, as of now, nice transitions between screens with Scaffold and screens without Scaffold are not possible with a single NavHost. Consider this example:

https://user-images.githubusercontent.com/6752601/133760459-819151c3-bd23-4785-9124-699be273dbbc.mp4

I need to wrap the NavHost for the two bottom bar destinations in a common Scaffold to properly animate the BottomBar. With this configuration, the transition to the image screen above the bottom bar (in z-direction) is only possible by adding a second NavHost, which contains the image screen and the main NavHost.

I see two options here:

• Make it possible to lay out some NavHost destinations above the top and bottom bar of the Scaffold. I don’t think this is currently possible in Compose, so this might be very difficult to implement.
• Add a NavGraphBuilder function which adds wrapping composables to certain destinations. In this case, both bottom bar destinations would be wrapped in such a function, which would add the Scaffold to these screens.

Probably, there are more options. Personally, I would favor the second option. I know, this is not really in scope of Accompanist, but since Accompanist Navigation currently contains the next-gen NavHost implementation, I wanted to start here.

What are your opinions on this?

[ianhanniballake]

FWIW, we’ll be continuing to look at this as part of the explorations into shared elements (part of the Jetpack Compose Roadmap and their integration into Navigation, which would be the mechanism you’d want to use share an element across multiple (but perhaps not all) screens.

That kind of solution would still only use a single NavHost though.

[fschuetz04]

By the way, a bare-bones implementation of the second approach: https://github.com/fschuetz04/compose-navigation-test.