如何使用Dagger Hilt在动态要素模块中创建ViewModel？

问题描述

尝试使用private val viewmodel: PostDetailviewmodel by viewmodels()在动态要素模块中创建viewmodel

片段

class PostDetailFragment : DynamicNavigationFragment<FragmentPostDetailBinding>() {

    private val viewmodel: PostDetailviewmodel by viewmodels()
    
    override fun getLayoutRes(): Int = R.layout.fragment_post_detail

    override fun bindViews() {
        // Get Post from navigation component arguments
        val post = arguments?.get("post") as Post
        dataBinding.item = post
        viewmodel.updatePostStatus(post)
        
    }

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

    private fun initCoreDependentInjection() {

        val coreModuleDependencies = EntryPointAccessors.fromApplication(
            requireActivity().applicationContext,DomainModuleDependencies::class.java
        )

        DaggerPostDetailComponent.factory().create(
            coreModuleDependencies,requireActivity().application
        )
            .inject(this)

    }
}

结果错误

Caused by: java.lang.InstantiationException: java.lang.class<com.x.post_detail.PostDetailviewmodel> has no zero argument constructor

它可以在应用模块中的任何片段中工作，但不能在动态功能模块中工作。将viewmodels添加到动态要素模块的正确方法是什么？我应该使用viewmodelFactory在应用模块中创建viewmodels并从应用模块中获取它们吗？

解决方法

基于此官方github帖子

现在可以在以下位置找到有关Hilt和DFM的文档 https://developer.android.com/training/dependency-injection/hilt-multi-module#dfm

通常，因为我们是基于子组件和 整体组件，您将无法使用标准的Hilt 带有DFM的@AndroidEntryPoint之类的机制。

不幸的是，没有。 @ViewModelInject使用击键 ActivityRetainedComponent是整体的，因此任何@ViewModelInject 您的DFM中的班级不会被识别。

到目前为止，似乎不可能仅在动态要素模块中使用@ViewModelInject和by viewModels()注入ViewModel。

基于格子应用程序，我将动态功能模块中的Dagger模块重建为

@InstallIn(FragmentComponent::class)
@Module
class PostDetailModule {

    @Provides
    fun providePostDetailViewModel(fragment: Fragment,factory: PostDetailViewModelFactory) =
        ViewModelProvider(fragment,factory).get(PostDetailViewModel::class.java)

    @Provides
    fun provideCoroutineScope() = CoroutineScope(Dispatchers.Main.immediate + SupervisorJob())

}

ViewModel和ViewModelFactory是

class PostDetailViewModel @ViewModelInject constructor(
    private val coroutineScope: CoroutineScope,private val getPostsUseCase: UseCase
) : ViewModel() {
 
    // Do other things
}

class PostDetailViewModelFactory @Inject constructor(
    private val coroutineScope: CoroutineScope,private val getPostsUseCase: UseCase
) : ViewModelProvider.Factory {

    @Suppress("UNCHECKED_CAST")
    override fun <T : ViewModel> create(modelClass: Class<T>): T {
        if (modelClass != PostDetailViewModel::class.java) {
            throw IllegalArgumentException("Unknown ViewModel class")
        }
        return PostDetailViewModel(
            coroutineScope,getPostsUseCase
        ) as T
    }
}

并注入到动态特征模块中的片段

class PostDetailFragment : Fragment() {

    @Inject
    lateinit var viewModel: PostDetailViewModel


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

    private fun initCoreDependentInjection() {

        val coreModuleDependencies = EntryPointAccessors.fromApplication(
            requireActivity().applicationContext,DomainModuleDependencies::class.java
        )

        DaggerPostDetailComponent.factory().create(
            dependentModule = coreModuleDependencies,fragment = this
        )
            .inject(this)
    }
}