So i’m trying to use the “dialog” feature on the n...

# compose

[mattinger]

So i’m trying to use the “dialog” feature on the navigation component. I’ve got things working mostly as i want, except for the handling of the back button. The back button should basically dismiss the dialog, which it does. However, i also want to run some code to insert a log statement when that happens. You can do this with the normal “Dialog” composable, via the onDismissRequest parameter. However, that seems to be missing from the navComponent.

[Ian Lake]

There's really two separate layers to consider:
1. The layer that owns the creation and dismissal of the Dialog
2. The content that is hosted within the Dialog

[Ian Lake]

In the Navigation world, that first layer is what the NavHost is doing for you. Callbacks for when a destination is shown / popped should be looking at the NavController's state as the source of truth i.e.,

val navController = rememberNavController()
val currentBackStackEntry by navController.currentBackStackEntryAsState()
if (currentBackStackEntry != null) {
  LaunchedEffect(logger, currentBackStackEntry) {
    // Log whenever the current destination changes
    logger.logCurrentScreen(currentBackStackEntry.destination.route)
  }
}

[Ian Lake]

For the second case where you are providing the content of a Dialog, AnimatedContent, etc., you'd generally use a DisposableEffect and specifically its onDispose to tell when that content goes out of scope - i.e., your dialog is no longer visible.

dialog("dialogRoute") { backStackEntry ->
  // This is the content within the Dialog
  DisposableEffect(logger) {
    logger.logScreenVisible(backStackEntry.destination.route)
    onDispose {
      logger.logScreenDismised(backStackEntry.destination.route)
    }
  }
}