Type safety improvements

app/src/main/java/no/nordicsemi/android/common/test/MainActivity.kt

@@ -35,8 +35,8 @@ import android.os.Bundle
 import androidx.activity.compose.setContent
 import dagger.hilt.android.AndroidEntryPoint
 import no.nordicsemi.android.common.navigation.NavigationView
-import no.nordicsemi.android.common.test.main.MainDestinations
-import no.nordicsemi.android.common.test.scanner.ScannerDestinations
+import no.nordicsemi.android.common.test.main.MainDestination
+import no.nordicsemi.android.common.test.scanner.ScannerDestination
 import no.nordicsemi.android.common.theme.NordicActivity
 import no.nordicsemi.android.common.theme.NordicTheme
 
@@ -48,7 +48,7 @@ class MainActivity : NordicActivity() {
 
         setContent {
             NordicTheme {
-                NavigationView(MainDestinations + ScannerDestinations)
+                NavigationView(MainDestination + ScannerDestination)
             }
         }
     }

app/src/main/java/no/nordicsemi/android/common/test/main/Main.kt

@@ -24,11 +24,9 @@ val Main = createSimpleDestination("main")
  *
  * Optionally, this can define a local Router for routing navigation within the module.
  */
-private val MainDestination = defineDestination(Main) {
-        MainScreen()
-    }
-
-val MainDestinations = MainDestination.asDestinations()
+val MainDestination = defineDestination(Main) {
+    MainScreen()
+}
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable

app/src/main/java/no/nordicsemi/android/common/test/main/page/BasicViewsPage.kt

@@ -21,9 +21,8 @@ import androidx.lifecycle.SavedStateHandle
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
-import kotlinx.coroutines.flow.launchIn
-import kotlinx.coroutines.flow.mapNotNull
-import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.flow.*
+import no.nordicsemi.android.common.navigation.NavigationResult
 import no.nordicsemi.android.common.navigation.Navigator
 import no.nordicsemi.android.common.test.R
 import no.nordicsemi.android.common.test.scanner.Scanner
@@ -58,7 +57,8 @@ class BasicPageViewModel @Inject constructor(
     init {
         navigator.resultFrom(Scanner)
             // Filter out results of cancelled navigation.
-            .mapNotNull { it }
+            .mapNotNull { it as? NavigationResult.Success }
+            .map { it.value }
             // Save the result in SavedStateHandle.
             .onEach { savedStateHandle[DEVICE_KEY] = it }
             // And finally, launch the flow in the ViewModelScope.

app/src/main/java/no/nordicsemi/android/common/test/scanner/Scanner.kt

@@ -1,44 +1,28 @@
 package no.nordicsemi.android.common.test.scanner
 
 import android.os.ParcelUuid
-import androidx.compose.runtime.collectAsState
-import androidx.compose.runtime.getValue
 import androidx.hilt.navigation.compose.hiltViewModel
-import androidx.lifecycle.SavedStateHandle
-import androidx.lifecycle.ViewModel
-import dagger.hilt.android.lifecycle.HiltViewModel
-import no.nordicsemi.android.common.navigation.*
+import no.nordicsemi.android.common.navigation.createDestination
+import no.nordicsemi.android.common.navigation.defineDestination
+import no.nordicsemi.android.common.navigation.viewmodel.SimpleNavigationViewModel
 import no.nordicsemi.android.common.ui.scanner.DeviceSelected
 import no.nordicsemi.android.common.ui.scanner.ScannerScreen
-import no.nordicsemi.android.common.ui.scanner.ScannerScreenResult
 import no.nordicsemi.android.common.ui.scanner.ScanningCancelled
 import no.nordicsemi.android.common.ui.scanner.model.DiscoveredBluetoothDevice
-import javax.inject.Inject
 
-val Scanner = createDestination<ParcelUuid, DiscoveredBluetoothDevice>("scanner")
+val Scanner = createDestination<ParcelUuid?, DiscoveredBluetoothDevice>("scanner")
 
-private val ScannerDestination = defineDestination(Scanner) {
-    val vm = hiltViewModel<ScannerViewModel>()
-    val uuid by vm.uuid.collectAsState()
+val ScannerDestination = defineDestination(Scanner) {
+    val vm: SimpleNavigationViewModel = hiltViewModel()
+    val uuid = vm.nullableParameterOf(Scanner)
 
-    ScannerScreen(uuid = uuid) {
-        vm.onEvent(it)
-    }
-}
-
-val ScannerDestinations = ScannerDestination.asDestinations()
-
-@HiltViewModel
-private class ScannerViewModel @Inject constructor(
-    private val navigator: Navigator,
-    savedStateHandle: SavedStateHandle,
-) : ViewModel() {
-    val uuid = savedStateHandle.getStateFlow(Scanner, null)
-
-    fun onEvent(event: ScannerScreenResult) {
-        when (event) {
-            is DeviceSelected -> navigator.navigateUpWithResult(Scanner, event.device)
-            ScanningCancelled -> navigator.navigateUp()
+    ScannerScreen(
+        uuid = uuid,
+        onResult = { result ->
+            when (result) {
+                is DeviceSelected -> vm.navigateUpWithResult(Scanner, result.device)
+                is ScanningCancelled -> vm.navigateUp()
+            }
         }
-    }
+    )
 }

navigation/src/main/java/no/nordicsemi/android/common/navigation/NavigationDestination.kt

@@ -59,25 +59,12 @@ data class NavigationDestination(
     val content: @Composable () -> Unit
 ) {
 
-    operator fun plus(other: NavigationDestination): NavigationDestinations {
-        return listOf(this, other).asDestinations()
+    operator fun plus(other: NavigationDestination): List<NavigationDestination> {
+        return listOf(this, other)
     }
-}
 
-/**
- * A collection of destinations.
- *
- * @property values List of destinations within a component.
- */
-class NavigationDestinations(
-    val values: List<NavigationDestination>,
-) {
-    constructor(
-        destination: NavigationDestination,
-    ) : this(listOf(destination))
-
-    operator fun plus(other: NavigationDestinations): NavigationDestinations {
-        return NavigationDestinations(values + other.values)
+    operator fun plus(other: List<NavigationDestination>): List<NavigationDestination> {
+        return listOf(this) + other
     }
 }
 
@@ -102,23 +89,4 @@ fun createSimpleDestination(name: String): DestinationId<Unit, Unit> = Destinati
 fun defineDestination(
     id: DestinationId<*, *>,
     content: @Composable () -> Unit
-): NavigationDestination = NavigationDestination(id, content)
-
-/**
- * Helper method for creating a [NavigationDestinations].
- *
- * This destination can be routed using global router specified
- * in the [NavigationView].
- */
-fun List<NavigationDestination>.asDestinations() =
-    NavigationDestinations(this)
-
-/**
- * Helper method for creating a [NavigationDestinations]
- * from a single destination.
- *
- * This destination can be routed using global router specified
- * in the [NavigationView].
- */
-fun NavigationDestination.asDestinations() =
-    NavigationDestinations(this)
+): NavigationDestination = NavigationDestination(id, content)

navigation/src/main/java/no/nordicsemi/android/common/navigation/NavigationResult.kt

@@ -0,0 +1,11 @@
+package no.nordicsemi.android.common.navigation
+
+/**
+ * The navigation result.
+ */
+sealed class NavigationResult<R> {
+    /** Navigation was cancelled. */
+    class Cancelled<R> : NavigationResult<R>()
+    /** The navigation has returned a result. */
+    data class Success<R>(val value: R) : NavigationResult<R>()
+}

navigation/src/main/java/no/nordicsemi/android/common/navigation/NavigationView.kt

@@ -42,7 +42,10 @@ import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.rememberNavController
-import no.nordicsemi.android.common.navigation.internal.*
+import no.nordicsemi.android.common.navigation.internal.Cancelled
+import no.nordicsemi.android.common.navigation.internal.NavigationViewModel
+import no.nordicsemi.android.common.navigation.internal.NavigationViewModel.Event
+import no.nordicsemi.android.common.navigation.internal.navigate
 
 /**
  * A navigation view allows navigating between different destinations.
@@ -53,7 +56,7 @@ import no.nordicsemi.android.common.navigation.internal.*
  */
 @Composable
 fun NavigationView(
-    destinations: NavigationDestinations,
+    destinations: List<NavigationDestination>,
 ) {
     val navHostController = rememberNavController()
 
@@ -63,8 +66,8 @@ fun NavigationView(
     val event by navigation.events.collectAsState()
     event?.let { e ->
         when (e) {
-            is NavigateTo -> navHostController.navigate(e.route, e.args)
-            is NavigateUp -> {
+            is Event.NavigateTo -> navHostController.navigate(e.route, e.args)
+            is Event.NavigateUp -> {
                 val activity = LocalContext.current as Activity
                 // Navigate up to the previous destination, passing the result.
                 navHostController.currentBackStackEntry?.destination?.route?.let { route ->
@@ -84,9 +87,9 @@ fun NavigationView(
 
     NavHost(
         navController = navHostController,
-        startDestination = destinations.values.first().id.name,
+        startDestination = destinations.first().id.name,
     ) {
-        destinations.values.forEach { destination ->
+        destinations.forEach { destination ->
             composable(
                 route = destination.id.name,
             ) {

navigation/src/main/java/no/nordicsemi/android/common/navigation/Navigator.kt

@@ -1,29 +1,31 @@
+@file:Suppress("unused")
+
 package no.nordicsemi.android.common.navigation
 
 import android.net.Uri
 import android.os.Bundle
 import androidx.lifecycle.SavedStateHandle
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.parcelize.RawValue
 
 interface Navigator {
 
     /**
      * Creates a flow that will emit the results of the navigation from the given destination.
      *
-     * Null is emitted when the navigation was cancelled.
-     *
      * @param from The origin destination to listen for results from.
      */
-    fun <R> resultFrom(from: DestinationId<*, R>): Flow<R?>
+    fun <R> resultFrom(from: DestinationId<*, R>): Flow<NavigationResult<R>>
 
     /**
      * Requests navigation to the given destination. An optional parameter can be passed.
      *
      * @param to The destination to navigate to.
-     * @param args An optional argument to pass to the destination.
+     * @param args An optional argument to pass to the destination. The argument will be saved
+     * in [SavedStateHandle], therefore it must be savable to a [Bundle].
      */
-    fun <A> navigateTo(to: DestinationId<A, *>, args: A? = null)
+    fun <A> navigateTo(to: DestinationId<A, *>, args: @RawValue A)
 
     /**
      * Navigates up to previous destination, or finishes the Activity.
@@ -35,10 +37,10 @@ interface Navigator {
      *
      * @param from The destination from which navigating up.
      * @param result The result, which will be passed to the previous destination.
-     * The returned type will be saved in [SavedStateHandle], therefore it must be
+     * The returned object will be saved in [SavedStateHandle], therefore it must be
      * savable to a [Bundle].
      */
-    fun <R> navigateUpWithResult(from: DestinationId<*, R>, result: R)
+    fun <R> navigateUpWithResult(from: DestinationId<*, R>, result: @RawValue R)
 
     /**
      * Opens the given link in a browser.
@@ -52,15 +54,20 @@ interface Navigator {
  * @param destination The current destination.
  */
 fun <A> SavedStateHandle.getStateFlow(destination: DestinationId<A, *>, initial: A?): StateFlow<A?> =
-    @Suppress("UNCHECKED_CAST")
-    getStateFlow<A?>(destination.name, initial)
+    getStateFlow(destination.name, initial)
+
+/**
+ * Returns the argument for the current destination.
+ *
+ * @param destination The current destination.
+ */
+fun <A> SavedStateHandle.getOrNull(destination: DestinationId<A?, *>): A? =
+    get(destination.name)
 
 /**
  * Returns the argument for the current destination.
  *
  * @param destination The current destination.
  */
-@Suppress("UNCHECKED_CAST")
-fun <A> SavedStateHandle.get(destination: DestinationId<A, *>): A? =
-    @Suppress("DEPRECATION")
-    get<Bundle?>(destination.name)?.get(destination.name) as? A
+fun <A> SavedStateHandle.get(destination: DestinationId<A & Any, *>): A =
+    get(destination.name) ?: error("Destination '${destination.name}' requires a non-nullable argument")

navigation/src/main/java/no/nordicsemi/android/common/navigation/internal/NavigationExecutor.kt

@@ -1,7 +1,33 @@
 package no.nordicsemi.android.common.navigation.internal
 
 import android.os.Bundle
+import android.os.Parcelable
+import androidx.core.os.bundleOf
 import androidx.lifecycle.SavedStateHandle
+import kotlinx.parcelize.Parcelize
+import kotlinx.parcelize.RawValue
+import no.nordicsemi.android.common.navigation.DestinationId
+
+/**
+ * Navigation target. This class wraps the destination and the parameter.
+ *
+ * @property destination The destination id.
+ * @property args Optional
+ */
+internal data class NavigationTarget<A>(
+    val destination: DestinationId<A, *>,
+    val args: @RawValue A
+) {
+    fun toBundle() = bundleOf(destination.name to args)
+}
+
+internal sealed class NavigationResultState
+@Parcelize
+internal object Initial : NavigationResultState(), Parcelable
+@Parcelize
+internal object Cancelled : NavigationResultState(), Parcelable
+@Parcelize
+internal data class Success<R>(val value: @RawValue R) : NavigationResultState(), Parcelable
 
 /**
  * A navigation executor that can be used to navigate to next destination, or back.
@@ -12,7 +38,7 @@ internal interface NavigationExecutor {
      *
      * @param target The target target with an optional parameter.
      */
-    fun navigate(target: NavigationTarget)
+    fun <A> navigate(target: NavigationTarget<A>)
 
     /**
      * Navigate up to the previous destination passing the given result.
@@ -21,5 +47,5 @@ internal interface NavigationExecutor {
      * The returned type will be saved in [SavedStateHandle], therefore it must be
      * savable to a [Bundle].
      */
-    fun navigateUpWithResult(result: NavigationResult)
+    fun navigateUpWithResult(result: NavigationResultState)
 }