Jetpack Compose + ViewModel + Navigation + Hilt + AssistedInject

Jetpack Compose + ViewModel + Navigation + Hilt の ViewModel で AssistedInject を使う方法。


ViewModelExt.kt

view plainprint?

1. @Composable  
2. inline fun <reified VM : ViewModel> assistedViewModel(  
3.     viewModelStoreOwner: ViewModelStoreOwner = checkNotNull(LocalViewModelStoreOwner.current) {  
4.         "No ViewModelStoreOwner was provided via LocalViewModelStoreOwner"  
5.     },  
6.     crossinline viewModelProducer: (SavedStateHandle) -> VM  
7. ): VM {  
8.     val factory = if (viewModelStoreOwner is NavBackStackEntry) {  
9.         object : AbstractSavedStateViewModelFactory(viewModelStoreOwner, viewModelStoreOwner.arguments) {  
10.             @Suppress("UNCHECKED_CAST")  
11.             override fun <T : ViewModel?> create(key: String, modelClass: Class<T>, handle: SavedStateHandle): T {  
12.                 return viewModelProducer(handle) as T  
13.             }  
14.         }  
15.     } else {  
16.         // Use the default factory provided by the ViewModelStoreOwner  
17.         // and assume it is an @AndroidEntryPoint annotated fragment or activity  
18.         null  
19.     }  
20.     return viewModel(viewModelStoreOwner, factory = factory)  
21. }  
22.   
23. fun Context.extractActivity(): Activity {  
24.     var ctx = this  
25.     while (ctx is ContextWrapper) {  
26.         if (ctx is Activity) {  
27.             return ctx  
28.         }  
29.         ctx = ctx.baseContext  
30.     }  
31.     throw IllegalStateException(  
32.         "Expected an activity context for creating a HiltViewModelFactory for a " +  
33.                 "NavBackStackEntry but instead found: $ctx"  
34.     )  
35. }  

@Composable inline fun <reified VM : ViewModel> assistedViewModel( viewModelStoreOwner: ViewModelStoreOwner = checkNotNull(LocalViewModelStoreOwner.current) { "No ViewModelStoreOwner was provided via LocalViewModelStoreOwner" }, crossinline viewModelProducer: (SavedStateHandle) -> VM ): VM { val factory = if (viewModelStoreOwner is NavBackStackEntry) { object : AbstractSavedStateViewModelFactory(viewModelStoreOwner, viewModelStoreOwner.arguments) { @Suppress("UNCHECKED_CAST") override fun <T : ViewModel?> create(key: String, modelClass: Class<T>, handle: SavedStateHandle): T { return viewModelProducer(handle) as T } } } else { // Use the default factory provided by the ViewModelStoreOwner // and assume it is an @AndroidEntryPoint annotated fragment or activity null } return viewModel(viewModelStoreOwner, factory = factory) } fun Context.extractActivity(): Activity { var ctx = this while (ctx is ContextWrapper) { if (ctx is Activity) { return ctx } ctx = ctx.baseContext } throw IllegalStateException( "Expected an activity context for creating a HiltViewModelFactory for a " + "NavBackStackEntry but instead found: $ctx" ) } MainActivity.kt

view plainprint?

1. @HiltAndroidApp  
2. class MyApplication : Application()  
3.   
4. @AndroidEntryPoint  
5. class MainActivity : ComponentActivity() {  
6.     override fun onCreate(savedInstanceState: Bundle?) {  
7.         super.onCreate(savedInstanceState)  
8.         setContent {  
9.             MaterialTheme {  
10.                 Surface(color = MaterialTheme.colors.background) {  
11.                     MyApp()  
12.                 }  
13.             }  
14.         }  
15.     }  
16. }  
17.   
18. @Composable  
19. fun MyApp() {  
20.     val navController = rememberNavController()  
21.   
22.     NavHost(navController, startDestination = "Screen1") {  
23.   
24.         composable("Screen1") {  
25.             LazyColumn(modifier = Modifier.fillMaxSize()) {  
26.                 items(20) {  
27.                     Text(  
28.                         text = "Item : $it",  
29.                         modifier = Modifier  
30.                             .fillMaxWidth()  
31.                             .clickable {  
32.                                 navController.navigate("Screen2/$it")  
33.                             }  
34.                             .padding(16.dp)  
35.                     )  
36.                 }  
37.             }  
38.         }  
39.   
40.         composable(  
41.             route = "Screen2/{id}",  
42.             arguments = listOf(  
43.                 navArgument("id") { type = NavType.IntType },  
44.             )  
45.         ) {  
46.             val arguments = requireNotNull(it.arguments)  
47.             val id = arguments.getInt("id")  
48.             val viewModel = assistedViewModel { savedStateHandle ->  
49.                 Screen2ViewModel.provideFactory(LocalContext.current)  
50.                     .create(savedStateHandle, id)  
51.             }  
52.   
53.             Screen2(viewModel)  
54.         }  
55.     }  
56. }  
57.   
58. @Composable  
59. fun Screen2(viewModel: Screen2ViewModel) {  
60.     Text(  
61.         text = viewModel.greet(),  
62.         modifier = Modifier.padding(24.dp)  
63.     )  
64. }  
65.   
66. class Screen2ViewModel @AssistedInject constructor(  
67.     private val nameProvider: NameProvider,  
68.     @Assisted private val savedStateHandle: SavedStateHandle,  
69.     @Assisted private val id: Int  
70. ) : ViewModel() {  
71.   
72.     @AssistedFactory  
73.     interface Factory {  
74.         fun create(savedStateHandle: SavedStateHandle, id: Int): Screen2ViewModel  
75.     }  
76.   
77.     @EntryPoint  
78.     @InstallIn(ActivityComponent::class)  
79.     interface ActivityCreatorEntryPoint {  
80.         fun getScreen2ViewModelFactory(): Factory  
81.     }  
82.   
83.     companion object {  
84.         fun provideFactory(context: Context): Factory {  
85.             val activity = context.extractActivity()  
86.             return EntryPoints.get(activity, ActivityCreatorEntryPoint::class.java)  
87.                 .getScreen2ViewModelFactory()  
88.         }  
89.     }  
90.   
91.     fun greet(): String {  
92.         return "Hello ${nameProvider.name()} : id = $id"  
93.     }  
94. }  
95.   
96. @Singleton  
97. class NameProvider @Inject constructor() {  
98.   
99.     fun name(): String {  
100.         return "Android"  
101.     }  
102. }  

@HiltAndroidApp class MyApplication : Application() @AndroidEntryPoint class MainActivity : ComponentActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContent { MaterialTheme { Surface(color = MaterialTheme.colors.background) { MyApp() } } } } } @Composable fun MyApp() { val navController = rememberNavController() NavHost(navController, startDestination = "Screen1") { composable("Screen1") { LazyColumn(modifier = Modifier.fillMaxSize()) { items(20) { Text( text = "Item : $it", modifier = Modifier .fillMaxWidth() .clickable { navController.navigate("Screen2/$it") } .padding(16.dp) ) } } } composable( route = "Screen2/{id}", arguments = listOf( navArgument("id") { type = NavType.IntType }, ) ) { val arguments = requireNotNull(it.arguments) val id = arguments.getInt("id") val viewModel = assistedViewModel { savedStateHandle -> Screen2ViewModel.provideFactory(LocalContext.current) .create(savedStateHandle, id) } Screen2(viewModel) } } } @Composable fun Screen2(viewModel: Screen2ViewModel) { Text( text = viewModel.greet(), modifier = Modifier.padding(24.dp) ) } class Screen2ViewModel @AssistedInject constructor( private val nameProvider: NameProvider, @Assisted private val savedStateHandle: SavedStateHandle, @Assisted private val id: Int ) : ViewModel() { @AssistedFactory interface Factory { fun create(savedStateHandle: SavedStateHandle, id: Int): Screen2ViewModel } @EntryPoint @InstallIn(ActivityComponent::class) interface ActivityCreatorEntryPoint { fun getScreen2ViewModelFactory(): Factory } companion object { fun provideFactory(context: Context): Factory { val activity = context.extractActivity() return EntryPoints.get(activity, ActivityCreatorEntryPoint::class.java) .getScreen2ViewModelFactory() } } fun greet(): String { return "Hello ${nameProvider.name()} : id = $id" } } @Singleton class NameProvider @Inject constructor() { fun name(): String { return "Android" } } Issue (https://github.com/google/dagger/issues/2287)　は 1月からあるけど、進んでなさそう。