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

Question

我怎样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 dagger 2，它运行良好。

下面是MyFirebaseMessagingService类：

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

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

下面是AppModuleDagger 2 的类

@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)
    }
}

是否可以为MyFirebaseMessagingService课堂提供数据库和 dao？

我尝试了上述方法来提供exampleOneDao给MyFirebaseMessagingService班级，但它抛出了以下内容Exception

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

谢谢你。

标签： androidfirebasekotlinfirebase-cloud-messagingdagger-2

Answer 1

终于从这个链接得到了解决方案：https ://github.com/googlesamples/android-architecture-components/issues/253

作为MyFirebaseMessagingService一个Service类，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项注入到 Service 类中。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）创建一个新模块来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) 在您的应用程序组件中注册您的新模块。

@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，覆盖添加 AndroidInjection.inject(this) 的服务的 onCreate 方法。

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)
    }


}