Is it impossible to preview a custom view that emb...

# compose

[louiscad]

Is it impossible to preview a custom view that embeds a ComposeView from Android Studio? It complains about missing ViewTreeLifecycleOwner, and ViewTressSavedStateRegistryOwner 😕

Also, does it mean it's impossible to have a compose view outisde of an Activity? I'm thinking about the few WindowManager use cases.

[Adam Powell]

File the former issue and no, you can create, configure, and drive both of those dependencies outside of an activity

[louiscad]

Are you sure about that?
From the interop APIs doc that I just checked out:

You must attach the ComposeView to a ViewTreeLifecycleOwner.

Getting a standalone ViewTreeLifecycleOwner instance for use in the WindowManager is not really possible, so I'm wondering how it's supposed to work 🤔

[Adam Powell]

Why do you think it's not possible?

[Adam Powell]

LifecycleOwner is just an interface and LifecycleRegistry is public

[louiscad]

There's also the non documented ViewTressSavedStateRegistryOwner that you can't fake

[louiscad]

When you use WindowManager, you don't have a Lifecycle. Making a custom one doesn't seem so great to me.

[Adam Powell]

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:savedsta[…]va/androidx/savedstate/SavedStateRegistryController.java;l=83

[Zach Klippenstein (he/him) [MOD]]

Making a custom lifecycle for this case is kind of like making a custom coroutine scope imo - ideally something the infrastructure does for you, but sometimes that infrastructure isn’t there (yet)

[Adam Powell]

right, and directly managing windows outside the scope of an activity is niche enough that paving this dirt road isn't likely to be a priority for a while.

[louiscad]

That "dirty road" which for now is only previewing via a View in the IDE, could be making an accessibility service, be it to customize the device, bring special features, or provide accessibility features. In any cases, I think it can be more… accessible 🙂

So I wrote all of this boilerplate:

val lifecycleOwner = object : LifecycleOwner {
            private val lifecycle = LifecycleRegistry(this)
            init {
                lifecycle.currentState = Lifecycle.State.STARTED
            }
            override fun getLifecycle(): Lifecycle = lifecycle
        }
        val savedStateRegistryOwner = object : SavedStateRegistryOwner {

            private val controller = SavedStateRegistryController.create(this)
            override fun getLifecycle() = lifecycleOwner.lifecycle
            override fun getSavedStateRegistry(): SavedStateRegistry = controller.savedStateRegistry
        }

ViewTreeLifecycleOwner.set(it.root, lifecycleOwner)
            ViewTreeSavedStateRegistryOwner.set(it.root, savedStateRegistryOwner)

But I still get an error:

java.lang.IllegalStateException: ViewTreeLifecycleOwner not found from com.android.layoutlib.bridge.impl.Layout{3feb6b45 V.E...... ......ID 0,0-0,0}   at androidx.compose.ui.platform.WindowRecomposer_androidKt.createLifecycleAwareViewTreeRecomposer(…)
…

[louiscad]

Created the issue: https://issuetracker.google.com/issues/187339385