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我有一个应该处理所有通知并因此扩展 FirebaseMessagingService 的类：

class DefaultFCMHandler(): FirebaseMessagingService(), FCMHandler, KodeinAware {

    private val _kodein: Kodein by closestKodein()

    override val kodein = Kodein.lazy {
        extend(_kodein)
    }

    private val authenticator: Authenticator by instance()

    override fun onNewToken(token: String) {
        // ...
    }

    override fun onMessageReceived(remoteMessage: RemoteMessage) {
        // ...
    }
}

在应用程序类中，我将所有内容绑定如下：

class MyApplication : Application(), KodeinAware {

    override val kodein = Kodein.lazy {
        // ...
        bind<Authenticator>() with singleton {
            DefaultAuthenticator(
                instance(),
                instance(),
                instance()
            )
        }
        // ...
        bind<FCMHandler>() with singleton {
            DefaultFCMHandler()
        }
    }
}

问题是，无论我尝试什么，我总是会遇到以下异常：

java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法 'android.content.Context android.content.Context.getApplicationContext()'

我不明白，因为基于此它应该可以访问上下文（我将应用程序文件放入清单中）。

我在 github 上找到了这个，但推广的解决方案并没有解决问题。

我可能对 DI 的工作原理有一个普遍的误解。

完整的堆栈跟踪如下：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: de.gitlab.user, PID: 14300
    java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
        at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:118)
        at org.kodein.di.android.ClosestKt.kodein(closest.kt:25)
        at org.kodein.di.android.ClosestKt.access$kodein(closest.kt:1)
        at org.kodein.di.android.ContextKodeinPropertyDelegateProvider$provideDelegate$1.invoke(closest.kt:39)
        at org.kodein.di.android.ContextKodeinPropertyDelegateProvider$provideDelegate$1.invoke(closest.kt:38)
        at kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74)
        at de.gitlab.user.data.fcm.DefaultFCMHandler.get_kodein(Unknown Source:7)
        at de.gitlab.user.data.fcm.DefaultFCMHandler.access$get_kodein$p(DefaultFCMHandler.kt:16)
        at de.gitlab.user.data.fcm.DefaultFCMHandler$kodein$1.invoke(DefaultFCMHandler.kt:21)
        at de.gitlab.user.data.fcm.DefaultFCMHandler$kodein$1.invoke(DefaultFCMHandler.kt:16)
        at org.kodein.di.internal.KodeinImpl$Companion.newBuilder(KodeinImpl.kt:22)
        at org.kodein.di.internal.KodeinImpl$Companion.access$newBuilder(KodeinImpl.kt:21)
        at org.kodein.di.internal.KodeinImpl.<init>(KodeinImpl.kt:19)
        at org.kodein.di.Kodein$Companion$lazy$1.invoke(Kodein.kt:447)
        at org.kodein.di.Kodein$Companion$lazy$1.invoke(Kodein.kt:429)
        at kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74)
        at org.kodein.di.LazyKodein.getBaseKodein(Unknown Source:7)
        at org.kodein.di.LazyKodein.getContainer(lateinit.kt:31)
        at org.kodein.di.KodeinAwareKt$Instance$1.invoke(KodeinAware.kt:176)
        at org.kodein.di.KodeinAwareKt$Instance$1.invoke(Unknown Source:4)
        at org.kodein.di.KodeinProperty$provideDelegate$1.invoke(properties.kt:42)
        at kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74)
        at de.gitlab.user.data.fcm.DefaultFCMHandler.getAuthenticator(Unknown Source:7)
        at de.gitlab.user.data.fcm.DefaultFCMHandler.sendRegistrationToServer(DefaultFCMHandler.kt:74)
        at de.gitlab.user.data.fcm.DefaultFCMHandler.access$sendRegistrationToServer(DefaultFCMHandler.kt:16)
        at de.gitlab.user.data.fcm.DefaultFCMHandler$submitToken$1.onComplete(DefaultFCMHandler.kt:50)
        at com.google.android.gms.tasks.zzj.run(Unknown Source:4)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
4

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