Using Dagger 2 to inject into service

Question

I have an app which is basically a service that runs all the time and alarms the user when something happens.

When the service creates the alarm, it needs to give it

Answer 1

I wrote the code from the top of my head, so there could be a typo or two.

You do it just the same as when injecting stuff into activities.

1. Declare a component,
2. add the inject method to that component,
3. add a module providing your service
4. create that components builder
5. add your module to the builder
6. inject your service with the component

Your module and component would look something like this (maybe add some scope)

@Module
class ServiceModule {

    MyService mService;

    ServiceModule(MyService service) {
        mService = service;
    }

    @Provides
    MyService provideMyService() {
        return mService;
    }
}

@Component(modules=ServiceModule.class)
interface MyServiceComponent {
    void inject(MyService service);
}

Then in onCreate just create your component and inject your alarm.

@Inject
private SomeAlarm alarm;

public void onCreate() {
    DaggerMyServiceComponent.builder()
            .serviceModule(new ServiceModule(this))
            .build()
            .inject(this);

    alarm.doStuff();
}

This is assuming that your alarm can be constructor injected by having an @Inject annotated constructor like this:

class SomeAlarm {
    @Inject
    SomeAlarm(MyService service) {
        /*constructor stuff*/
    }
}

Else you would just also add the alarm creation to your module.

Answer 2

I know this question already has an answer but there are an other way to do this

first make your application extend HasServiceInjector like this:

public class App extends Application implements HasActivityInjector, 
HasServiceInjector {

@Inject
DispatchingAndroidInjector<Activity> dispatchingActivityInjector;
@Inject
DispatchingAndroidInjector<Service> dispatchingServiceInjector;

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

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

@Override
public AndroidInjector<Service> serviceInjector() {
    return dispatchingServiceInjector;
}

}

then create a ServiceBuilderModule this will perform injection over services:

@Module
abstract class ServiceBuilderModule {

@ContributesAndroidInjector
abstract MyService contributeMyService();

}

then register the new module to your component

@Component(modules = {
    AndroidSupportInjectionModule.class,
    AppModule.class,
    ActivityBuilderModule.class,
    ServiceBuilderModule.class
 })
 @Singleton
 public interface AppComponent {

 @Component.Builder
 interface Builder {
    @BindsInstance
    Builder application(App application);

    AppComponent build();
 }

 void inject(App app);

 }

then override the onCreate method of your service and add AndroidInjection.inject(this) like below code :

public class MyService extends Service {

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

@Nullable
@Override
public IBinder onBind(Intent intent) {
    return null;
}

}

code in kotlin is exact conversion of the code above. hope this helps some coders from now on.