如果没有@Provides方法，则无法提供Dagger 2 Named [英] Dagger 2 Named cannot be provided without a @Provides method

问题描述

尝试使用Dagger 2并与命名提供者发生问题.我有一个简单的设置，如下所示:

Trying to grok Dagger 2 and having an issue with named providers. I have a simple setup as follows:

// Module
@Module
class AppModule(private val app: App) {
    @Provides @AppScope fun providesApp() = app

    @Provides @AppScope fun provideSharedPreferences(app: App) = PreferenceManager.getDefaultSharedPreferences(app)

    @Provides @AppScope @Named("Uri1") fun providesUri1() = Uri.Builder().scheme("https").authority("authory1").build()

    @Provides @AppScope @Named("Uri2") fun providesUri2() = Uri.Builder().scheme("https").authority("authory2").build()
}

// Component
@AppScope
@Component(modules = arrayOf(AppModule::class))
interface AppComponent {
    fun inject(target: MainActivity)
}

// MainActivity
@Inject @AppScope lateinit var preferences: SharedPreferences
@Inject @AppScope @Named("Uri1") lateinit var uri1: Uri
@Inject @AppScope @Named("Uri2") lateinit var uri2: Uri

在重建项目时，我会得到:

When rebuilding my project I am given:

Error:Gradle: android.net.Uri cannot be provided without an @Provides- or @Produces-annotated method.

我不明白为什么添加命名的限定词对我来说不起作用.如果删除这些，则可以毫无问题地获取SharedPreferences实例.

I don't understand why adding the Named qualifier doesn't work for me here. If I remove these I can get an instance of SharedPreferences without issue.

任何对我正在做错事的见解都将受到赞赏！

Any insight into what I'm doing wrong would be appreciated!

每个建议的更改具有与上述相同的结果.

Changes per suggestions with the same results as above.

// New module
@Module
class AppModule(private val app: App) {
    @Provides @AppScope fun providesApp() = app

    @Provides @AppScope fun provideSharedPreferences(app: App) = PreferenceManager.getDefaultSharedPreferences(app)

    @Provides @AppScope @Tag("Uri1") fun providesUri1(): Uri = Uri.Builder().scheme("https").authority("authority1").build()

    @Provides @AppScope @Tag("Uri2") fun providesUri2(): Uri = Uri.Builder().scheme("https").authority("authority2").build()
}

// Tag annotation
@Qualifier
@Retention(AnnotationRetention.RUNTIME)
annotation class Tag(val tag: String = "")

// MainActivity
@Inject @AppScope lateinit var preferences: SharedPreferences
@Inject @AppScope @Tag("Uri1") lateinit var uri1: Uri
@Inject @AppScope @Tag("Uri2") lateinit var uri2: Uri

项目仓库@ Github

推荐答案

我认为我发现了问题(至少我检查了您的项目并正确生成了dagger类).如果需要注入使用@Named或某些@Qualifier注释注释的字段，则必须使用这种语法:

I think I found the problem (at least I checked out your project and it generated dagger classes correctly). If you need to inject fields annotated with @Named or some @Qualifier annotation you have to use this kind of syntax:

class MainActivity : AppCompatActivity() {
    @Inject lateinit var preferences: SharedPreferences
    @Inject @field:[Named ("Uri1")] lateinit var uri1: Uri // for @Named annotation or...
    @Inject @field:Uri2 lateinit var uri2: Uri // ...for @Qualifier annotation

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

        app().component.inject(this)

        println(uri1)
        println(uri2)
    }
}

注意@Named/限定词注释如何进入@field:(本身没有@).

Notice how @Named / qualifier annotation goes inside @field: (without @ itself).

从此回购.

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