Dagger2 将演示者注入 Kotlin Activity 错误

Question

我使用 dragger2 将演示器注入 Kotlin Activity，演示器为空，这是我的代码：

class CategoryDetailActivity : MvpActivity<ProductFilterView,ProductFilterPresenter>(), ProductFilterView {
private lateinit var presenter: ProductFilterPresenter
    @Inject set       


 override fun onCreate(savedInstanceState: Bundle?) {
        initialInjector()
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_category_detail)
        initData()
        initEvent()
    }
private fun initialInjector() {
    DaggerProductFilterComponent.builder()
            .applicationComponent(applicationComponent)
            .productFilterModule(ProductFilterModule())
            .build()
            .inject(this)
}
override fun getPresenter(): ProductFilterPresenter {
    return presenter!!
}

}

getPresenter()方法在MvpActivity的onCreate()中调用，MvpActivity是javaclass。初始演示者需要 ProductFilterModule 提供的一些实例，我猜也许演示者应该在组件注入后初始。当我运行时，它抛出 KotlinNullPointerException，演示者为 Null。

time: FATAL EXCEPTION: main
                                                                       Process: com.chiquedoll.chiquedoll, PID: 10617
                                                                       java.lang.RuntimeException: Unable to start activity ComponentInfo{com.chiquedoll.chiquedoll/com.chiquedoll.chiquedoll.view.activity.CategoryDetailActivity}: kotlin.KotlinNullPointerException
                                                                           at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                                                                           at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                                                                           at android.app.ActivityThread.-wrap11(ActivityThread.java)
                                                                           at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                                                                           at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                           at android.os.Looper.loop(Looper.java:148)
                                                                           at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                           at java.lang.reflect.Method.invoke(Native Method)
                                                                           at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                                        Caused by: kotlin.KotlinNullPointerException
                                                                           at com.chiquedoll.chiquedoll.view.activity.CategoryDetailActivity.getPresenter(CategoryDetailActivity.kt:281)
                                                                           at com.chiquedoll.chiquedoll.view.activity.CategoryDetailActivity.getPresenter(CategoryDetailActivity.kt:36)
                                                                           at com.chiquedoll.chiquedoll.view.activity.MvpActivity.onCreate(MvpActivity.java:19)
                                                                           at com.chiquedoll.chiquedoll.view.activity.CategoryDetailActivity.onCreate(CategoryDetailActivity.kt:65)
                                                                           at android.app.Activity.performCreate(Activity.java:6237)

如果我用java来做，没问题。

Answer 1

Dagger 2 不使用 setter 来注入字段，它直接分配值。因此，正确的版本是：

@Inject internal lateinit var presenter: ProductFilterPresenter

请注意，Dagger 2 要求可注入字段至少为 internal，private 将不起作用。

Dagger2 将演示者注入 Kotlin Activity 错误

Dagger2 inject a presenter into a Kotlin Activity error

android

kotlin

dagger-2

kotlin-android-extensions