android - Dagger-Hilt @ViewModelInject sharedViewModel 不注入(inject) fragment

Question

我正在尝试使用 Jetpack tutorial 在 fragment 和 Activity 之间创建共享注入(inject) View 模型.
共享 View 模型成功注入(inject)到父级 MyActivity 中，但是当渲染子级时，由于依赖注入(inject)失败，应用程序崩溃。我在下面提供了创建问题的代码。
提供 session 管理器:

@InstallIn(ApplicationComponent::class)
@Module
class AppModule {
    @Provides
    @Singleton
    fun provideSessionManager(
        networkClient: NetworkClient
    ): SessionManager {
        return SessionManager(networkClient)
    }
}

注入(inject)共享 View 模型:

class SharedViewModel @ViewModelInject constructor(
    private var sessionManager: SessionManager
) : ViewModel() {

    var name = MutableLiveData<String>("Shared View Model")
}

并且被父 Activity 和子 fragment 使用。

class MyActionFragment() : Fragment() {
    private val viewModel: SharedViewModel by viewModels()
    override fun onActivityCreated(savedInstanceState: Bundle?) {
       super.onActivityCreated(savedInstanceState)
       Timber.d("View Model Name 1: ${viewModel.name.value}") // This line crashes
    }
}

class MyActivity : AuthenticatedBaseActivity() {
    private val viewModel: SharedViewModel by viewModels()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Timber.d("View Model Name 2: ${viewModel.name.value}") // This line prints
    }
}

但是，当代码运行时，请注意 Activity 创建了 ViewModel 并访问了它的值，但是当 fragment 尝试这样做时，应用程序崩溃了:

**D/MyActivity: View Model Name 2: Shared View Model**
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.xxx.xxx, PID: 16630
    java.lang.RuntimeException: Cannot create an instance of class com.xxx.xxx.ui.main.SharedViewModel
        at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:221)
        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:278)
        at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
        at androidx.lifecycle.ViewModelLazy.getValue(ViewModelProvider.kt:54)
        at androidx.lifecycle.ViewModelLazy.getValue(ViewModelProvider.kt:41)
        at com.xxx.xxx.ui.main.MyActionFragment.getViewModel(Unknown Source:2)
        at com.xxx.xxx.ui.main.MyActionFragment.onActivityCreated(**MyActionFragment.kt:140**)
        at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2718)

此外，当我删除注入(inject)的 Hilt 依赖项 sessionManager fragment 和 View 模型的创建没有问题。
关注 this post没有运气。
非常感谢有关使用共享模型的 Hilt View 模型依赖注入(inject)的任何帮助!谢谢!

Answer 1

您可以在 中使用扩展功能 fragment :

class MyFragment: Fragment() {
    private val viewModel: SharedViewModel by activityViewModels()
}

在 Activity :

class MyActivity : Activity() {
    private val viewModel: SharedViewModel by viewModels()
}