Dagger2+Kotlin:lateinit属性尚未初始化

Question

我试图将ViewModelFactory注入到活动中，但它总是抛出同样的错误：lateinit属性ViewModelFactory尚未初始化。我找不到我可能做错了什么。请参阅上面我的类中的代码

AppComponent.kt

@Component(modules = [(AppModule::class), (NetworkModule::class), (MainModule::class)])
interface AppComponent {

    fun inject(application: TweetSentimentsApplication)

    fun inject(mainActivity: MainActivity)

    fun context(): Context

    fun retrofit(): Retrofit
}

@Module
class MainModule {

    @Provides
    fun mainViewModelFactorty(repository: TweetRepository): MainViewModelFactory = MainViewModelFactory(repository)

    @Provides
    fun local(database: AppDatabase): TweetLocal = TweetLocal(database)

    @Provides
    fun remote(tweetService: TweetService): TweetRemote = TweetRemote(tweetService)

    @Provides
    fun tweetService(retrofit: Retrofit): TweetService = retrofit.create(TweetService::class.java)

    @Provides
    fun repository(local: TweetLocal, remote: TweetRemote): TweetRepository = TweetRepository(local, remote)

}

class MainActivity : AppCompatActivity() {

    @Inject lateinit var viewModelFactory: MainViewModelFactory

    private val viewModel: MainViewModel? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main_activity)

        ViewModelProviders.of(this, viewModelFactory).get(MainViewModel::class.java)

        viewModel?.init("guuilp")
        viewModel?.getTweetList()?.observe(this, Observer {
            Toast.makeText(this, it?.size.toString(), Toast.LENGTH_LONG).show()
        })
    }
}

TweetSentimentsApplication.kt

open class TweetSentimentsApplication: Application(){

    companion object {
        lateinit var appComponent: AppComponent
    }

    override fun onCreate() {
        super.onCreate()

        initDI()
    }

    private fun initDI() {
        appComponent = DaggerAppComponent.builder()
                .appModule(AppModule(this))
                .build()
    }
}

Answer 1

在初始化MainActivity时，必须调用在appcomponent中定义的inject(MainActivity:MainActivity)方法，Dagger实际上就是这样注入所需的依赖项的。

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.main_activity)

    // This is where the dependencies are injected
    TweetSentimentsApplication.appComponent.inject(this)

    ViewModelProviders.of(this, viewModelFactory).get(MainViewModel::class.java)

    ...
}