Hello, `BackHandler` doesn't work inside `BottomSh...

# compose

[galex]

Hello, BackHandler doesn't work inside BottomSheetDialogFragment , how can I intercept it on the dialog and forward it myself to Compose which is the UI within BottomSheetDialog ?

[galex]

So if anyone is looking for the answer to this issue, it seems like the dialog is the one catching the onBackPressed event and dismisses the dialog.

To have Compose be connected to it, we have to do the following:

In your fragment, catches the dialog when created:

private lateinit var dialog: ComponentDialog

override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
    return BottomSheetDialog(requireContext(), theme).apply {
        fullyExpanded()
        notDraggable()
        withoutBackgroundDim()
    }.also { dialog = it }
}

Prepare the following extensions on `ComponentDialog`:

private val ComponentDialog.asBackPressedDispatcherOwner: OnBackPressedDispatcherOwner
        get() = object : OnBackPressedDispatcherOwner {
            override val lifecycle: Lifecycle
                get() = [e-mail]
            override val onBackPressedDispatcher: OnBackPressedDispatcher
                get() = [e-mail]
        }

And then the only missing piece is in your ComposeView to wrap the content with `CompositionLocalProvider`:

CompositionLocalProvider(
    LocalOnBackPressedDispatcherOwner provides dialog.asBackPressedDispatcherOwner
) {
    MainChatScreen(::dismiss)
}

Maybe @Ian Lake will tell me I missed something else, but in the meantime this seems to work 🤔

[Ian Lake]

ComponentDialog already implements OnBackPressedDispatcherOwner as of Activity 1.5.0: https://developer.android.com/jetpack/androidx/releases/activity#1.5.0

[Ian Lake]

And AppCompatDialog already extends from ComponentDialog as of AppCompat 1.5.0-alpha01: https://developer.android.com/jetpack/androidx/releases/appcompat#1.5.0-alpha01

[Ian Lake]

And with this change, AppCompatDialog already sets the correct ViewTreeOnBackPressedDispatcherOwner on the returned dialog so that LocalOnBackPressedDispatcherOwner picks it up

[Ian Lake]

And that change landed on March 16, so I'd expect it to be in the next AppCompat release (e.g., 1.7.0-alpha03)

[Ian Lake]

In the mean time, I'd probably just set the ViewTreeOnBackPressedDispatcherOwner on your Dialog window's decorView

[Ian Lake]

I assume you're already setting the ViewTreeLifecycleOwner and ViewTreeSavedStateRegistryOwner just to get your ComposeView to work in the BottomSheetDialog?

[galex]

No I wasn't, and that's actually much better (no need to retain the dialog):

override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
        return BottomSheetDialog(requireContext(), theme).apply {
            (...)
            initViewTreeOwners()
        }
    }

Here's it setting those itsefl:

private fun ComponentDialog.initViewTreeOwners() {
    window?.decorView?.let {
        it.setViewTreeLifecycleOwner(this)
        it.setViewTreeOnBackPressedDispatcherOwner(this)
        it.setViewTreeSavedStateRegistryOwner(this)
    }
}

Thanks for the whole explanation and update on AppCompat release, I will be able to remove this at some point!