Hilt 2.52中AssistedInject ViewModel使用报错排查求助

报错信息：

java.lang.IllegalStateException: Found @HiltViewModel-annotated class UserProfileViewModel using @AssistedInject but no creation callback was provided in CreationExtras.

ViewModel定义 #

@HiltViewModel(assistedFactory = UserProfileViewModel.Factory::class)
class UserProfileViewModel @AssistedInject constructor(
    private val sharedPreferences: EngClubSharedPreferences,
    private val authRepository: AuthRepository,
    private val resourceRepo: FileResourceRepository,
    @ApplicationContext private val context: Context,
    @Assisted private val user: User?
): ViewModel() {
    @AssistedFactory
    interface Factory {
        fun create(user: User?): UserProfileViewModel
    }
}

Composable调用代码 #

@Composable
fun UserProfileScreen(
    modifier: Modifier = Modifier,
    isSessionUser: Boolean = true,
    user: User? = sessionUser,
    onNavigateUp: () -> Unit,
    onLogoutOrDeletedAccount: () -> Unit
) {
    val navController = rememberNavController()
    val viewModel: UserProfileViewModel = hiltViewModel(
        creationCallback = { factory: UserProfileViewModel.Factory -> factory.create(user) }
    )
    
    NavHost(
        modifier = modifier.fillMaxSize(),
        navController = navController,
        startDestination = ProfileViewingScreen.route
    ) {
        composable(route = ProfileViewingScreen.route) {
            UserProfileViewingScreen(
                isSessionUser = isSessionUser,
                viewModel = viewModel,
                onNavigateUp = onNavigateUp,
                navigateToEditScreen = { navController.navigate(EditProfileScreen.route) },
                onLogoutOrDeletedAccount = onLogoutOrDeletedAccount
            )
        }
     }
}

用户疑问：该错误的原因是什么？代码库其他地方类似配置能正常运行，是不是遗漏了什么？

其他正常运行的代码示例 #

composable(
   route = "${MessageClubRoute.path}?groupID={groupID}",
   arguments = listOf(navArgument("groupID") {
                 type = NavType.StringType
                 defaultValue = ""
               }
              )
 ) {
  val groupID = it.arguments?.getString("groupID")
  val messagingClubViewModel = hiltViewModel<MessageClubViewModel,MessageClubViewModel.Factory>(
        creationCallback = { factory -> factory.create(groupID = "$groupID") }
     )

  MessageClubRoomNavigation(viewModel = messagingClubViewModel)
}

错误原因：你在NavHost外部调用hiltViewModel创建ViewModel，而Hilt的hiltViewModel函数依赖Navigation的NavBackStackEntry上下文才能正确传递包含creationCallback的CreationExtras。

对比正常代码就能看到差异：正常代码是在composable的lambda内部创建ViewModel，这里会自动获取当前路由对应的NavBackStackEntry，能把creationCallback正确注入到Hilt的创建流程中；而你的用户资料页面代码在NavHost外初始化ViewModel，此时没有对应的导航栈上下文，导致Hilt找不到你提供的creationCallback，从而抛出异常。

修正方法：将ViewModel的创建逻辑移到composable的lambda内部，也就是UserProfileViewingScreen所在的代码块里：

@Composable
fun UserProfileScreen(
    modifier: Modifier = Modifier,
    isSessionUser: Boolean = true,
    user: User? = sessionUser,
    onNavigateUp: () -> Unit,
    onLogoutOrDeletedAccount: () -> Unit
) {
    val navController = rememberNavController()
    
    NavHost(
        modifier = modifier.fillMaxSize(),
        navController = navController,
        startDestination = ProfileViewingScreen.route
    ) {
        composable(route = ProfileViewingScreen.route) {
            // 移到此处创建ViewModel
            val viewModel: UserProfileViewModel = hiltViewModel(
                creationCallback = { factory: UserProfileViewModel.Factory -> factory.create(user) }
            )
            UserProfileViewingScreen(
                isSessionUser = isSessionUser,
                viewModel = viewModel,
                onNavigateUp = onNavigateUp,
                navigateToEditScreen = { navController.navigate(EditProfileScreen.route) },
                onLogoutOrDeletedAccount = onLogoutOrDeletedAccount
            )
        }
     }
}

这样hiltViewModel就能获取当前路由的NavBackStackEntry上下文，正确传递creationCallback给Hilt，解决崩溃问题。

内容的提问来源于stack exchange，提问作者Nnaoma miracle