I know we have `BackHandler` in CMP now. But how c...

# multiplatform

[Karen Frangulyan]

I know we have BackHandler in CMP now. But how can I call the back press handler manually, for example, on a button click?
On Android I can simply use LocalOnBackPressedDispatcherOwner.current and I can be sure that the correct back press logic will work, like calling a BackHandler if someone installed it, or falling back to nav controller if not (I’m on Nav2). Is there something similar in CMP?

[Vilgot Fredenberg]

You should migrate to navigationevent and use LocalNavigationEventDispatcherOwner. I've created a helper function and then call DirectNavigationEventInput::backCompleted to go back.

@Composable
fun rememberNavigationEventInput(): DirectNavigationEventInput {
    val input = remember { DirectNavigationEventInput() }
    LocalNavigationEventDispatcherOwner.current?.navigationEventDispatcher?.let { dispatcher ->
        DisposableEffect(dispatcher) {
            dispatcher.addInput(input)
            onDispose { dispatcher.removeInput(input) }
        }
    }
    return input
}

[Karen Frangulyan]

@Vilgot Fredenberg thanks! Couple of questions:
• I assume navigationevent doesn’t depend on navigation library version? Can I use it with navigation 2?
• Do I need to provide navigation event dispatcher or is it coming out of the box with CMP? seems like I need to add an extra dependency at least.

[Vilgot Fredenberg]

• I don't know exactly how it's all wired up with nav 2 and CMP (I target Android and use nav3), but LocalOnBackPressedDispatcherOwner, for example, just forwards stuff to LocalNavigationEventDispatcherOwner. Briefly looking through compose-multiplatform-core, I can see a lot of references to it as well.
• It should be set up by compose for you (ComponentActivity in the case of Android) and you should therefore already (transitively) depend upon it