如何使用 Dagger2 提供 GoogleSignInOptions？

Question

I am trying to make small Firebase login app using Dagger2, but I have a problem with GoogleSignInOptions. I want to set it in the AppModule, but.requestIdToken have an error with: (getString(R.string.default_web_client_id)) Is my approach with GoogleSignInOptions appropriate? Maybe it's the wrong way? Sorry for that, but I am little confused about injection of the Firebase stuff.

@Module
class AppModule {

@Provides
fun getApp(application: Application?): Boolean {
    return application == null
}

@Singleton
@Provides
fun provideFirebaseAuthInstance(): FirebaseAuth {
    return FirebaseAuth.getInstance()
}

@Singleton
@Provides
fun provideGoogleSignInClient() : GoogleSignInOptions {

   return GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
        .requestIdToken(getString(R.string.default_web_client_id)) //here is a problem
        .requestEmail()
        .build()
}

}

Answer 1

Pass application object as parameter and use it to get required string

@Singleton
@Provides
fun provideGoogleSignInClient(application: Application) : GoogleSignInOptions {

   return GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
        .requestIdToken(application.applicationContext.getString(R.string.default_web_client_id))
        .requestEmail()
        .build()
    }

Answer 2

You need to get a Context in order to use the getString() method.

One way to fix it would be to make the application context available there.

You would modify your Application subclass to add a application context reference:

class App : Application(),
        HasSupportFragmentInjector,
        HasActivityInjector {

    @Inject
    lateinit var activityInjector: DispatchingAndroidInjector<Activity>

    @Inject
    lateinit var supportfragmentInjector: DispatchingAndroidInjector<Fragment>

    override fun onCreate() {
        super.onCreate()
        appContext = this
        DaggerApplicationComponent
                .create()
                .inject(this)
    }

    override fun activityInjector(): AndroidInjector<Activity> = activityInjector

    override fun supportFragmentInjector(): AndroidInjector<Fragment> = supportfragmentInjector
}

lateinit var appContext: Context
    internal set

Then you can use that appContext reference in your dependency injection module:

@Singleton
@Provides
fun provideGoogleSignInClient() : GoogleSignInOptions {

    return GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
            .requestIdToken(appContext.getString(R.string.default_web_client_id))
            .requestEmail()
            .build()
}

Another option would be to use dependency injection to provide the application context, see here for more info: https://github.com/google/dagger/issues/832