Keeping multiple active child nodes in BackStack

[saket]

Hey folks, I'm trying to create a navigation system where at least two nodes are active at all times in BackStack. This is to mostly to support screens with transparent backgrounds. Is this something that's doable right now without rolling out my own NavModel?

[KovalevAndrey]

Hi @saket, BackStack implementation of NavModel doesn't allow to do that but we have a separate API for that. Check out ParentNode's PermanentChild. It allows you to keep associated Node in the PermanentNavModel alive as long as ParenNode is alive

[KovalevAndrey]

Wops, I even forgot it was sealed. You could play with it in your own fork to see if defining your own operations does the job for you. In the mean time you can submit a feature request for allowing clients to define their own operations

[saket]

I can try!

BackStackSlider depends on transition operations for calculating offset animations. What would this when block look like if BackStackOperation isn't sealed?

appyx/core/src/main/kotlin/com/bumble/appyx/navmodel/backstack/transitionhandler/BackStackSlider.kt

Line 50 in 6c9d75d

when (val operation = descriptor.operation as? BackStackOperation) {

[KovalevAndrey]

this means that we should add else branch for any other operations and define a behaviour for them. For instance, toOutsideRight(width). This is not a big deal as clients can easily create their own transition handlers

[zsoltk]

@saket It's sealed only for purposes of transition handling (exhaustive when) and we were considering keeping it open.

However we went this way, as a core concept of the library is that you can implement your own navigation models with whatever states you wish anyway.

We even had an example with a "card stack" having more than one ACTIVE state.

[KovalevAndrey]

#130 sealed interface is removed