Dagger2 缺少绑定无法提供视图模型密钥

Question

我正在尝试使用具有多重绑定的 Dagger2 创建我的 ViewModel 的依赖注入，但我收到此错误并且无法使其工作，我尝试了几个答案(如下(，但没有一个帮助我。

这是我收到的错误：

SaveMyHeroApplicationComponent.java:8: error: [Dagger/MissingBinding] java.util.Map<java.lang.Class<? extends androidx.lifecycle.ViewModel>,javax.inject.Provider<androidx.lifecycle.ViewModel>> cannot be provided without an @Provides-annotated method.

---

这是我的代码

class SaveMyHeroApplication : DaggerApplication() {
override fun applicationInjector(): AndroidInjector<out DaggerApplication> {
return DaggerSaveMyHeroApplicationComponent.factory().create(this)
}
}

@Singleton
@Component(modules = [AndroidInjectionModule::class, MainActivityModule::class])
interface SaveMyHeroApplicationComponent : AndroidInjector<SaveMyHeroApplication> {
@Component.Factory
interface Factory {
fun create(@BindsInstance context: Context): SaveMyHeroApplicationComponent
}
}

@Module(includes = [NetworkModule::class, HomeModule::class])
class MainActivityModule {
@Provides
fun provideViewModelFactoryProviders(
providers: Map<Class<out ViewModel>, @JvmSuppressWildcards Provider<ViewModel>>
): ViewModelProvider.Factory = SaveMyHeroViewModelFactory(providers)
}

class SaveMyHeroViewModelFactory(
private val providers: Map<Class<out ViewModel>, Provider<ViewModel>>
) : ViewModelProvider.Factory {
override fun <T : ViewModel> create(modelClass: Class<T>): T =
requireNotNull(getProvider(modelClass).get()) {
"Provider for $modelClass returned null"
}

private fun <T : ViewModel> getProvider(modelClass: Class<T>): Provider<T> =
try {
requireNotNull(providers[modelClass] as Provider<T>) {
"No ViewModel provider is bound for class $modelClass"
}
} catch (error: ClassCastException) {
error("Wrong provider type registered for ViewModel type $error")
}
}

@Module(includes = [HomeModule.ProvideViewModel::class])
abstract class HomeModule {
@ContributesAndroidInjector(modules = [InjectViewModel::class])
abstract fun bind(): HomeFragment
@Module
class ProvideViewModel {
@Provides
@IntoMap
@ViewModelKey(HomeViewModel::class)
fun provideHomeViewModel() = HomeViewModel()
}
@Module
class InjectViewModel {
@Provides
fun provideHomeViewModel(
factory: ViewModelProvider.Factory,
target: HomeFragment
) = ViewModelProvider(target, factory).get(HomeViewModel::class.java)
}
}

@MustBeDocumented
@Target(
AnnotationTarget.FUNCTION,
AnnotationTarget.PROPERTY_GETTER,
AnnotationTarget.PROPERTY_SETTER
)
@Retention(AnnotationRetention.RUNTIME)
@MapKey
annotation class ViewModelKey(val value: KClass<out ViewModel>)

另外，这些是我的应用程序依赖项版本：

kotlin_version = ‘1.3.72'
dagger_version = ‘2.27’
gradle:3.6.3

我知道这个问题有几个问题，但我尝试了其中的几个，但没有一个对我有用。

这是我尝试阅读和检查的解决方案链接：

https://github.com/android/architecture-components-samples/tree/master/GithubBrowserSample

https://github.com/google/dagger/issues/1478

Dagger/MissingBinding java.util.Map<？>，Provider> 如果没有@Provides注释的方法，则无法提供

https://github.com/google/dagger/issues/1478

错误 [Dagger/MissingBinding] androidx.lifecycle.ViewModelProvider.Factory 无法在没有@Provides注释方法的情况下提供

https://medium.com/chili-labs/android-viewmodel-injection-with-dagger-f0061d3402ff

https://github.com/ChiliLabs/viewmodel-dagger-example

Answer 1

尝试使用架构蓝图示例(dagger-安卓分支(作为示例。

daggerAndroid本身就是一团糟，重要的是要遵循一些模板，以免走错路。也许您的方法也可以修复，但我建议您尝试更改您的架构：

1. 自定义视图模型工厂应在构造函数中具有@Inject：

class SaveMyHeroViewModelFactory @Inject constructor(
private val creators:  @JvmSuppressWildcards Map<Class<out ViewModel>, Provider<ViewModel>>
) : ViewModelProvider.Factory {
.......

2. 您应该添加辅助模块 ViewModelBuilderModule，该模块为 ViewModelProvider.Factory(您注入到所有活动和片段中(和自定义 ViewModel.Factory：

@Module
abstract class ViewModelBuilderModule {
@Binds
abstract fun bindViewModelFactory(factory: SaveMyHeroViewModelFactory): ViewModelProvider.Factory
}

3. 对于所有配对 - Activitiy/ViewModel 和 Fragment/ViewModel，您应该像这样添加模块(但您可以为所有模块制作单个模块，这取决于您(：

@Module
abstract class HomeModule {
@ContributesAndroidInjector(modules = [ViewModelBuilderModule::class])
internal abstract fun bind(): HomeFragment
@Binds
@IntoMap
@ViewModelKey(HomeViewModel::class)
internal abstract fun provideHomeViewModel(viewModel: HomeViewModel): ViewModel
}

4. 在 Dagger 组件中，您应该使用步骤 3 中的所有模块：

@Singleton
@Component(modules = [AndroidSupportInjectionModule::class, HomeModule::class, ...])
interface SaveMyHeroApplicationComponent : AndroidInjector<SaveMyHeroApplication> {
@Component.Factory
interface Factory {
fun create(@BindsInstance context: Context): SaveMyHeroApplicationComponent
}
}