用KClass类型绑定到映射 [英] Binding Into Map With KClass Type
问题描述
我试图通过KClass
类型将ViewModel
的子类绑定到映射中:
I am trying to bind subclasses of ViewModel
into a map by their KClass
types:
@Module abstract class ViewModelModule {
@Binds @IntoMap @ViewModelKey(MyViewModel::class)
abstract fun bindsMyViewModel(viewModel: MyViewModel): ViewModel
@Binds abstract fun bindViewModelFactory(factory: ViewModelFactory): ViewModelProvider.Factory
}
但是我收到Dagger编译器错误:
But I am getting Dagger compiler error:
e: ~/Example/app/build/tmp/kapt3/stubs/debug/com/example/app/injection/AppComponent.java:5: error: [dagger.android.AndroidInjector.inject(T)] java.util.Map<kotlin.reflect.KClass<? extends android.arch.lifecycle.ViewModel>,? extends javax.inject.Provider<android.arch.lifecycle.ViewModel>> cannot be provided without an @Provides-annotated method.
e:
e: public abstract interface AppComponent {
e: ^
e: java.util.Map<kotlin.reflect.KClass<? extends android.arch.lifecycle.ViewModel>,? extends javax.inject.Provider<android.arch.lifecycle.ViewModel>> is injected at
e: com.example.app.ui.ViewModelFactory.<init>(creators)
e: com.example.app.ui.ViewModelFactory is injected at
e: com.example.app.injection.ViewModelModule.bindViewModelFactory(p0)
e: android.arch.lifecycle.ViewModelProvider.Factory is injected at
e: com.example.app.ui.MyFragment.setViewModelFactory(p0)
e: com.example.app.ui.MyFragment is injected at
e: dagger.android.AndroidInjector.inject(arg0)
上面的ViewModelModule
包含在我的AppModule
中,这是我的AppComponent
中的一个模块.因此Dagger应该能够提供我的ViewModelFactory
所需的Map<KClass<out ViewModel>, Provider<ViewModel>>
,但是我无法弄清楚为什么它崩溃了.
The above ViewModelModule
is included in my AppModule
, which is a module in my AppComponent
. So Dagger should be able to provide the Map<KClass<out ViewModel>, Provider<ViewModel>>
required by my ViewModelFactory
, but I cannot figure out why it is crashing.
我还尝试将ViewModelKey
注释类切换到Java,将Class
用作构造函数参数而不是KClass
.然后将我的ViewModelFactory
修改为依赖于Map<Class<out ViewModel>, Provider<ViewModel>>
,但是发生了相同的错误.
I also tried switching the ViewModelKey
annotation class over to Java, taking a Class
as a constructor parameter instead of a KClass
. Then modified my ViewModelFactory
to depend on a Map<Class<out ViewModel>, Provider<ViewModel>>
, but the same error occurred.
推荐答案
在注释中使用KClass
时,实际上已编译为Java的Class
.但是实际的问题是Kotlin编译器正在生成的java.util.Map<kotlin.reflect.KClass<? extends android.arch.lifecycle.ViewModel>,? extends javax.inject.Provider<android.arch.lifecycle.ViewModel>>
通配符.
When using KClass
in an annotation, it actually gets compiled to Java's Class
. But the actual issue is the wildcard in java.util.Map<kotlin.reflect.KClass<? extends android.arch.lifecycle.ViewModel>,? extends javax.inject.Provider<android.arch.lifecycle.ViewModel>>
that the Kotlin compiler is generating.
假设@ViewModelKey
被定义为
@MapKey
annotation class ViewModelKey(val value: KClass<out ViewModel>)
您需要将注射部位定义为
You'll need to define your injection site as
Map<Class<out ViewModel>, @JvmSuppressWildcards Provider<ViewModel>>
使用@JvmSuppressWildcards
将阻止编译器生成通配符.
Using @JvmSuppressWildcards
will prevent the compiler from generating wildcards.
我实际上不知道,为什么Dagger编译器不支持通配符.您可以在此处看到类似的问题:
I don't actually know, why wildcards are not supported by the Dagger compiler. You can see a similar issue here: Dagger 2: How to inject Map<Class<? extends Foo>, Provider<? extends Foo>>
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