关于android：Dagger2将演示者注入Kotlin活动错误

Dagger2 inject a presenter into a Kotlin Activity error

我使用dragger2将演示者注入Kotlin活动中，演示者为null，这是我的代码：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

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!!
}

} ??

在MvpActivity的onCreate()中调用方法getPresenter()，并且MvpActivity是一个Java类。最初，演示者需要由ProductFilterModule提供的某些实例，也许我应该在组件注入后演示者是初始的。当我运行时，抛出KotlinNullPointerException，演示者为Null。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

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)

如果我使用Java来做，那没问题。

Dagger 2不使用setter来注入字段，而是直接分配值。因此，正确的版本将是：

1	@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。