Kotlin 和 Dagger：我可以对一个对象使用 @Inject 仍然使它成为 nullable/optional 吗？

Question

由于某些设备上发生的运行时错误，我需要一些可以使我的 class nullable/optional 的东西。

这可能吗？

class MyFragment extends Fragment {
    @Inject
    var presenter: MyPresenter? = null
// Other codes here...
}

我想使用 presenter 作为一个选项，因为 SOME 的旧 Android 设备尤其会抛出此错误（这是在我删除之前惰性初始化）。

代码：

class MyFragment extends Fragment {
    @Inject
    lazyinit var presenter: MyPresenter? = null
// Other codes here...

     override fun onDestroy() {
        super.onDestroy()
        presenter.somecode()
    }
}

错误：

Fatal Exception: java.lang.RuntimeException: Unable to destroy activity {com.sample.MyActivity}: c.r: lateinit property presenter has not been initialized
       at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3497)
       at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3515)
       at android.app.ActivityThread.access00(ActivityThread.java:135)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1249)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:136)
       at android.app.ActivityThread.main(ActivityThread.java:5017)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:515)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
       at dalvik.system.NativeStart.main(NativeStart.java)
Caused by c.r: lateinit property presenter has not been initialized
       at com.sample.MyFragment.onDestroy(SourceFile:459)
       at android.support.v4.app.Fragment.performDestroy(SourceFile:2434)
       at android.support.v4.app.FragmentManagerImpl.moveToState(SourceFile:1442)
       at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(SourceFile:1528)
       at android.support.v4.app.FragmentManagerImpl.moveToState(SourceFile:1595)
       at android.support.v4.app.FragmentManagerImpl.dispatchDestroy(SourceFile:2951)
       at android.support.v4.app.FragmentController.dispatchDestroy(SourceFile:271)
       at android.support.v4.app.FragmentActivity.onDestroy(SourceFile:390)
       at android.support.v7.app.AppCompatActivity.onDestroy(SourceFile:209)
       at android.app.Activity.performDestroy(Activity.java:5403)
       at android.app.Instrumentation.callActivityOnDestroy(Instrumentation.java:1117)
       at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3484)
       at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3515)
       at android.app.ActivityThread.access00(ActivityThread.java:135)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1249)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:136)
       at android.app.ActivityThread.main(ActivityThread.java:5017)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:515)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
       at dalvik.system.NativeStart.main(NativeStart.java)

是否有针对这种情况的方法或解决方法？

Answer 1

我遇到了同样的问题，并这样解决了：

@Inject
@JvmField
var presenter: Presenter? = null

希望对您有所帮助。

Answer 2

如果您没有需要访问 presenter 字段的 Java 代码，则无需使用 @JvmField 对其进行注释。相反，您可以像这样声明您的字段：

@set:Inject
var presenter: Presenter? = null

Kotlin 和 Dagger：我可以对一个对象使用 @Inject 仍然使它成为 nullable/optional 吗？

Kotlin and Dagger: Can I use @Inject to an object still make it nullable/optional?

kotlin

dagger-2