为片段定义注入器时，MVVM 工厂中的 Dagger2 编译错误

Question

我有一个下一个根组件：

@Singleton
@Component(modules = [AndroidInjectionModule::class,
        AndroidSupportInjectionModule::class, 
        ActivityBuilderModule::class])
interface RootComponent : AndroidInjector<DaggerApplication> {
    fun inject(myApplication: MyApplication)
    override fun inject(photoPartyApplication: DaggerApplication)

    @Component.Builder
    interface Builder {
        @BindsInstance
        fun application(application: Application): Builder
        fun build(): RootComponent
    }
}

在 ActivityBuilderModule 中：

@Module
abstract class ActivityBuilderModule {

    @ContributesAndroidInjector(modules = [MainActivityModule::class,
            ViewModelModule::class])
    @ActivityScope
    abstract fun bindMainActivity(): MainActivity

    @ContributesAndroidInjector(modules = [SecondaryActivityModule::class,
            ViewModelModule::class,
            FragmentBuilderModule::class])
    @ActivityScope
    abstract fun bindSecondaryActivity(): SecondaryActivity

}

ViewModelModule 是一个简单的模块，可帮助在 ViewModel 类中进行构造函数注入，由特定实例之间的 @Binds 和 ViewModel 类型组成。

MainActivityModule 和SecondaryActivityModule 为相应的活动定义了具体的依赖关系。

关键是当我添加这个 FragmentBuilderModule - 编译开始发出错误。堆栈跟踪是下一个：

错误：[Dagger/MissingBinding] some_package.SpecificDependency 不能在没有@Inject 构造函数或@Provides-annotated 方法的情况下提供。

公共抽象接口 RootComponent 扩展 dagger.android.AndroidInjector {

^

组件中存在具有匹配键的绑定：some_package.ActivityBuilderModule_BindMainActivity.MainActivitySubcomponent

some_package.SpecificDependency 被注入到 some_package.MainViewModel(specificDependency, …)

some_package.MainViewModel 在 some_package.ViewModelModule.mainViewModel(viewModel) 注入

Map<Class<? extends ViewModel>, Provider<ViewModel>> is injected at
      some_package.ViewModelFactory(viewModelProviders)

some_package.ViewModelFactory 在 some_package.ViewModelModule.bindViewModelFactory(factory) 注入

android.arch.lifecycle.ViewModelProvider.Factory 在 some_package.MyFragment.viewModelFactory 注入

some_package.MyFragment 在 dagger.android.AndroidInjector.inject(T) 处注入

[some_package.RootComponent → some_package.ActivityBuilderModule_BindSecondaryActivity.SecondaryActivitySubcomponent → some_package.FragmentBuilderModule_ProvideMyFragmentFactoryMyFragmentSubcomponent]

据我所知，Dagger 假设必须为Class<? extends ViewModel> -> Provider<ViewModel> 的map 正确构建整个依赖关系图，如果某些ViewModels 落入factory，并且factory 是注入到组件中，然后如果组件将要求 any viewmodel，必须交付。为了交付所有viewmodels，再次，所有依赖项都必须可用（这是不正确的，因为MainViewModel 的特定依赖项只能从MainModule 获得，这就是dagger 在堆栈跟踪之前所说的)。

是否有一种解决方法可以按需提供对Class<? extends ViewModel> -> Provider<ViewModel> 的map 的依赖关系，而不是在编译时构建整个图（这会导致编译时错误）

Answer 1

首先在RootComponent处添加ViewModelModule

 @Singleton
 @Component(modules = [AndroidInjectionModule::class,
            AndroidSupportInjectionModule::class, 
            ActivityBuilderModule::class,
            ViewModelModule::class])                 // add this so you don't have to add for every activity
    interface RootComponent : AndroidInjector<DaggerApplication> {
        fun inject(myApplication: MyApplication)
        override fun inject(photoPartyApplication: DaggerApplication)

        @Component.Builder
        interface Builder {
            @BindsInstance
            fun application(application: Application): Builder
            fun build(): RootComponent
        }
    }

现在在 ActivityBuilderModule 中只添加活动

 @Module
 abstract class ActivityBuilderModule {

    @ContributesAndroidInjector
    @ActivityScope
    abstract fun bindMainActivity(): MainActivity
 }

现在在 ViewModelModule 中添加所有 ViewModel

 @Module
 abstract class ViewModelModule {

    @Binds
    @IntoMap
    @ViewModelKey(MainActivityModule::class)
    abstract fun bindMainActivityViewModel(mainActivityViewModel: MainActivityModule): ViewModel
}

添加 ViewModelKey

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

和 ViewModelFactory

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

    @Suppress("UNCHECKED_CAST")
    override fun <T : ViewModel> create(modelClass: Class<T>): T {
        var creator: Provider<out ViewModel>? = creators[modelClass]
        if (creator == null) {
            for ((key, value) in creators) {
                if (modelClass.isAssignableFrom(key)) {
                    creator = value
                    break
                }
            }
        }
        if (creator == null) {
            throw IllegalArgumentException("unknown model class $modelClass")
        }
        try {
            Timber.d(creator.toString())
            return creator.get() as T
        } catch (e: Exception) {
            throw RuntimeException(e)
        }
    }
}