Hello, I'm trying to pass a state to the navigation for me to use in the screen, i tried just passin...

# compose

[Felipe Passos]

Hello, I'm trying to pass a state to the navigation for me to use in the screen, i tried just passing the location to the navhost but it does not update when the variable does so i found it out about this hilt thing, but i'm getting a runtime error..

[Colton Idle]

@Felipe Passos can you edit your post to put the code in this thread please?

[Colton Idle]

https://kotlinlang.slack.com/archives/CJLTWPH7S/p1616265877303000

[Felipe Passos]

Oh, okay

[Felipe Passos]

I'm trying to pass a state to the navigation for me to use in the screen, i tried just passing the location to the navhost but it does not update when the variable does so i found it out about this hilt thing, so i added the dependencies
on the main build file

dependencies {
        classpath 'com.android.tools.build:gradle:7.0.0-alpha14'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.4.31"
        classpath "com.google.dagger:hilt-android-gradle-plugin:2.35"
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }

and in the app build file:

implementation "com.google.dagger:hilt-android:2.35"
    implementation "androidx.hilt:hilt-navigation-compose:1.0.0-alpha01"

Added this line to the main file:

@AndroidEntryPoint
class MainActivity : ComponentActivity() {
    private val _tag = "TAXI"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

and on the navHost :

@Composable
fun SearchNavigator(location: String) {
    val navController = rememberNavController()
    Log.d("LOCATION_IN_NAV", location)
    Column(
        modifier = Modifier
            .background(white)
            .padding(vertical = 10.dp)
            .fillMaxHeight()
            .fillMaxWidth()
    ) {

        NavHost(navController, startDestination = "MainSearch") {
            composable("MainSearch") { backStackEntry ->
                val viewModel = hiltNavGraphViewModel<LocationViewModel>(backStackEntry = backStackEntry)
                Log.d("LOCATION_IN_SEARCH", viewModel.name.hasObservers().toString())

                Form(location, navController)

But i'm getting a runtime error saying that the AndroidEntryPoint is not setted :

2021-04-27 07:52:57.310 10438-10438/com.gotootaxi E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.gotootaxi, PID: 10438
    java.lang.IllegalStateException: Given component holder class com.gotootaxi.MainActivity does not implement interface dagger.hilt.internal.GeneratedComponent or interface dagger.hilt.internal.GeneratedComponentManager
        at dagger.hilt.EntryPoints.get(EntryPoints.java:62)

What i'm doing wrong?

[Adam Powell]

Skipping the hilt and ViewModel stuff entirely, I think there's still an outstanding issue where the nav graph built by the NavHost composable does not update for recompositions, which in this case means the new lambda capture for a new parameter value of location won't be applied.

[Adam Powell]

You can work around this by doing val currentLocation by rememberUpdatedState(location) as the first line of the SearchNavigator function, then use currentLocation instead of location everywhere else in your snippet.

[Adam Powell]

cc @Jeremy Woods

[Felipe Passos]

Wow, that worked

[Felipe Passos]

I was trying to found something to make this work and could not find it and this simple solution worked, thank you very much!

[Adam Powell]

in your defense, the reasons the original code didn't work and why the workaround does are not simple 🙂 I think your original expectations were correct and our code isn't meeting those expectations today

[Jeremy Woods]

Yeah, we are taking a closer look at NavGraph in base navigation to see how best to handle this case. I think it could be a little more dynamic in general so these types of use cases just work.