android 带有刀柄的 ViewModelFactory

Question

我首先尝试 android ViewModel 和 Hilt DI

据我了解 link，要在运行时使用值初始化 ViewModel，我应该使用 ViewModelFactory

//ViewModel
class ScoreViewModel(finalScore: Int) : ViewModel() {
   // The final score
   var score = finalScore
   init {
       Log.i("ScoreViewModel", "Final score is $finalScore")
   }
}

//ViewModelFactory
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
   if (modelClass.isAssignableFrom(ScoreViewModel::class.java)) {
       return ScoreViewModel(finalScore) as T
   }
   throw IllegalArgumentException("Unknown ViewModel class")
}


//Fragment
viewModelFactory = ScoreViewModelFactory(ScoreFragmentArgs.fromBundle(arguments!!).score)

要使用带刀柄的 ViewModel，我应该使用 @ViewModelInject，如下所述 link

Hilt and Jetpack integrations

//ViewModel
class ExampleViewModel @ViewModelInject constructor(
  private val repository: ExampleRepository,
  @Assisted private val savedStateHandle: SavedStateHandle
) : ViewModel() {
  ...
}

//Activity / Fragment
@AndroidEntryPoint
class ExampleActivity : AppCompatActivity() {
  private val exampleViewModel: ExampleViewModel by viewModels()
  ...
}

但是如何将 Hilt 与 ViewModelFactory 一起使用？

似乎答案在 @Assisted 中，但我不知道如何

如何告诉 hilt 我喜欢它向 ViewModel 注入存储库接口，同时仍然允许 ViewModelFactory 在运行时使用参数初始化 ViewModel？

Answer 1

将您的 ScoreViewModelFactory 传递到 viewModel 的内置 ktx 扩展中。您还可以通过将 SavedStateHandle 本身与 defaultViewModelProviderFactory 一起使用来使用 Activity/Fragment 个参数。

/*
Gradle Dependencies
def lifecycle_version = "2.2.0"
def hiltLifeVersion = "1.0.0-alpha01"
def hiltVersion = "2.28.1-alpha"
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
implementation "androidx.lifecycle:lifecycle-viewmodel-savedstate:$lifecycle_version"
implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
implementation "com.google.dagger:hilt-android:$hiltVersion"
implementation "androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha01"
implementation "androidx.hilt:hilt-work:$hiltLifeVersion"
implementation "androidx.hilt:hilt-common:1.0.0-alpha01"
kapt "com.google.dagger:hilt-android-compiler:$hiltVersion"
kapt "androidx.hilt:hilt-compiler:$hiltLifeVersion"
*/

import androidx.fragment.app.viewModels

@AndroidEntryPoint
class ExampleFragment : Fragment(R.layout.example_fragment) {

    //internally using defaultViewModelProviderFactory 
    private val viewModel : ExampleViewModel by viewModels()

    //or you own viewmodal factory instance --> scoreViewModelFactory
    private val viewModel : ExampleViewModel by viewModels { scoreViewModelFactory }

}

class ExampleViewModel @ViewModelInject constructor(
    private val repository: ExampleRepository,
    @Assisted override val savedStateHandle: SavedStateHandle
) : ViewModel() {

    //bundle args -> String, Int, Parcelable etc.. 
    private val arg1LiveData: MutableLiveData<String> = 
                         savedStateHandle.getLiveData("arg1", "")

}

在片段视图模型的内置 ktx 扩展中

@MainThread
inline fun <reified VM : ViewModel> Fragment.viewModels(
    noinline ownerProducer: () -> ViewModelStoreOwner = { this },
    noinline factoryProducer: (() -> Factory)? = null
) = createViewModelLazy(VM::class, { ownerProducer().viewModelStore }, factoryProducer)

Answer 2

感谢@Elye，接下来的文章帮了大忙。我推荐阅读。

Passing Activity Intent Data to ViewModel through Injection

Injecting ViewModel with Dagger Hilt

似乎不需要大部分工厂，因为大多数 viewmodel 初始参数取自先前的片段，可以通过 SavedStateHandle 访问，如果标记为 @Assisted[=21= 则自动注入]

为了设置刀柄，我使用了以下代码实验室教程

Using Hilt in your Android app

然后，viewModel 仅使用下一个代码自动完成注入

请注意，如 fabioCollini here, it seems savedStateHandle can also get values from safe args 所述，只需将参数名称作为键即可。事实上，这就是我在下面的例子中所做的。 ps：为了让安全参数更“安全”，我确实尝试用 ItemsFragmentArgs 替换 SavedStateHandle 希望它能工作，但应用程序没有编译。我希望它能在未来实现（如果已经实现，请告诉我）

//ItemFragment file
@AndroidEntryPoint
class ItemsFragment : Fragment() {

    private val viewModel: ItemsViewModel by viewModels()

    //use viewModel as you would. No need to initialize.
}

//Module file - if you have any repository, remember to bind it 
//or provide the exact implementation as noted in code-labs
@InstallIn(ApplicationComponent::class)
@Module
abstract class DatabaseModuleBinder {

    @Binds
    abstract fun bindGlistRepository(impl: FirestoreGlistRepository): GlistRepository

}


//ItemsViewModel file - lastly, anotate as follows and take your arguments 
//from savedStateHandle (for safe args, use variable name as key)
class ItemsViewModel @ViewModelInject constructor(private val glistRepo: GlistRepository,
                     @Assisted private val savedStateHandle: SavedStateHandle) : ViewModel() {

    private val glistLiveDate = glistRepo.getGlistLiveData(
        savedStateHandle.get<String>("listId")!!
    )

..
}

希望对ps任何人有所帮助，如果有任何错误，请告诉我

android 带有刀柄的 ViewModelFactory

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