I am finally starting with Navigation but I am stu...

# compose

[Nat Strangerweather]

I am finally starting with Navigation but I am stuck with a basic problem:

Scaffold(
            scaffoldState = scaffoldState,
            drawerContent = {
                HomePageDrawer()
            },

For HomePageDrawer() I get : "No value passed for parameter 'navController'". What am I supposed to put for parameter navController? Whatever I try gives me a nullpointer... Basically I have some items in my drawer and I want to navigate to other screens from them...

[Ian Lake]

The Getting Started part of the guide (https://developer.android.com/jetpack/compose/navigation#getting-started) states that you should be using rememberNavController() outside of your Scaffold

[Ian Lake]

I.e., in a place where every Composable that needs to access it can access it

[Nat Strangerweather]

I'm using it in my navigation composable:

@Composable
fun ApplicationNavigation() {
    val navController = rememberNavController()
    androidx.navigation.compose.NavHost(
        navController = navController,
        startDestination = "homepage"
    ) {
        composable("homepage") {
            HomePage()
        }
        composable("drawer"){
            HomePageDrawer(navController)
        }
        composable("placeholder"){
            PlaceHolder()
        }
    }

But how can I refer to it in my HomePage Scaffold? I'm a bit confused.

[Nat Strangerweather]

Hmm, I'll try to do what you suggested and as the doc indicates, thanks.

[Ian Lake]

Just pass in navController

[Nikola Drljaca]

You could also consider passing a lambda instead of passing the navController, that way you can keep all navigation related code in one place and not pass the navController around

[Nat Strangerweather]

@Nikola Drljaca Thanks for this, I'm interested in your idea. Would you be able to show me how it would look, if you have the time? Maybe with my example above?

[Nikola Drljaca]

Well, here is a quick example of something thats similar to what I use. For your example, I think you can pass the lambda down your composable tree to wherever you need to call navigate(). Maybe the parent of the scaffold can have a lambda and pass it to the HomePageDrawer() . Anyway, here's a gist https://gist.github.com/nikolaDrljaca/06013137c325638ac6b71ca3ac76c681

[Nikola Drljaca]

Of course, this might not be the "proper" way to do it, but to me it seemed cleaner than passing the navController everywhere.

[Nat Strangerweather]

Thanks for this, really appreciate it

[Ian Lake]

Yep, that's actually the recommended practice to make your composables separately testable (from a bit farther down that exact same page I linked earlier): https://developer.android.com/jetpack/compose/navigation#testing

[Nat Strangerweather]

Oh excellent, thanks, I really need to start reading the doc more carefully! 😉