如何使用Dagger 2向MyFirebaseMessagingService提供数据库,以便我可以在android中本地存储fcm消息

Question

如何才能将数据库实例传递给MyFirebaseMessagingService扩展的类,FirebaseMessagingService以便我可以data在本地保存有效负载？

注意:我已经在我的应用程序中设置了匕首2,它运行正常.

以下是MyFirebaseMessagingService课程:

class MyFirebaseMessagingService @Inject constructor(exampleOneDao: ExampleOneDao?) : FirebaseMessagingService() {

    override fun onMessageReceived(remoteMessage: RemoteMessage?) {
    //need db instance to store data payload locally (Room)
    }
}

以下是AppModuleDagger 2 的等级

@Module(includes = arrayOf(ViewModelModule::class))
class AppModule() {

    // --- DATABASE INJECTION ---
    @Provides
    @Singleton
    internal fun provideDatabase(application: Application): MyDatabase {
        return Room.databaseBuilder(application,
               MyDatabase::class.java, "MyDatabase.db")
              .build()
    }

    @Provides
    @Singleton
    internal fun provideExampleOneDao(database: MyDatabase): ExampleOneDao {
        return database.exampleOneDao()
    }

    @Provides
    @Singleton
    internal fun provideMyFirebaseMessagingService(exampleOneDao: 
        ExampleOneDao): MyFirebaseMessagingService {
           return MyFirebaseMessagingService(exampleOneDao)
    }
}

是否可以向类提供数据库和dao MyFirebaseMessagingService？

我试过上面的方法提供exampleOneDao给MyFirebaseMessagingService类,但它抛出以下内容Exception

MyFirebaseMessagingService: java.lang.InstantiationException: java.lang.Class<com.example.user.app.firebase.messaging.MyFirebaseMessagingService> has no zero argument constructor

谢谢.

Answer 1

最后通过以下链接获得解决方案:https://github.com/googlesamples/android-architecture-components/issues/253

作为MyFirebaseMessagingService一个Service类,因此对于类中的注入Service,Dagger提供了一种方法,通过它我们可以将依赖注入Service类.以下是在服务类中启用注入的步骤:

1)使Application实现HasServiceInjector并为服务注入DispatchingAndroidInjector.

public class App extends Application implements HasActivityInjector, HasServiceInjector {

    @Inject
    DispatchingAndroidInjector<Activity> dispatchingActivityInjector;

    // Add this line
    @Inject
    DispatchingAndroidInjector<Service> dispatchingServiceInjector;

    @Override
    public void onCreate() {
        super.onCreate();
        AppInjector.init(this);
    }

    @Override
    public AndroidInjector<Activity> activityInjector() {
        return dispatchingActivityInjector;
    }

    // override this method after implementing HasServiceInjector
    @Override
    public AndroidInjector<Service> serviceInjector() {
        return dispatchingServiceInjector;
    }

}

2)创建一个新模块以对您的服务执行注入.

@Module
abstract class ServiceBuilderModule {

    // for my case, the service class which needs injection is MyFirebaseMessagingService
    @ContributesAndroidInjector
    abstract MyFirebaseMessagingService contributeMyFirebaseMessagingService();

}

3)在应用程序的组件中注册新模块.

@Component(modules = {
        AndroidSupportInjectionModule.class,
        AppModule.class,
        ActivityBuilderModule.class,
        // Need to define previously created module class here
        ServiceBuilderModule.class
})
@Singleton
public interface AppComponent {
    @Component.Builder
    interface Builder {
        @BindsInstance
        Builder application(App application);
        AppComponent build();
    }
    void inject(App app);
}

4)最后,重写方法onCreate添加AndroidInjection.inject(this)的服务.

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    //So now we are able to inject here same as we do in Activity. No need for constructor injection
    @Inject ExampleOneDao exampleOneDao

    // Override this method first
    @Override
    public void onCreate() {
        AndroidInjection.inject(this);
        super.onCreate();
    }

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        // use your dao here to store remoteMessage data payload into your database, e.g exampleOneDao.save(somethingHere)
    }


}