Brtdku

I'm using MVVM structure with Data Binding in my project. Things get weird when it comes to GG/FB Sign In, because they need Context

googleApiClient = new GoogleApiClient.Builder(context)

            .enableAutoManage(this, this)

            .addApi(Auth.GOOGLE_SIGN_IN_API, gso)

            .build();

Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(googleApiClient);

startActivityForResult(signInIntent, GOOGLE_AUTH);

GoogleApiClient needs Context so I can't pass it to ViewModel, which receives DataBinding events.

class LoginViewModel(

    dataManager: DataManager,

    schedulerProvider: SchedulerProvider

) : BaseViewModel<LoginNavigator>(dataManager, schedulerProvider) {



    fun loginGoogle(){

        setIsLoading(true)

        //No idea what to write in here

    }

}

Is there any way to use Gg/FB Sign In with MVVM structure ? Or I just have to do the original way (do everything in Activity) ?

It is very simple thanks to @Erik Browne and Kotlin’s Function literals with receiver

Create SingleLiveEvent

Create LiveMessageEvent

class LiveMessageEvent<T> : SingleLiveEvent<(T.() -> Unit)?>() {



    fun setEventReceiver(owner: LifecycleOwner, receiver: T) {

        observe(owner, Observer { event ->

            if ( event != null ) {

                receiver.event()

            }

        })

    }



    fun sendEvent(event: (T.() -> Unit)?) {

        value = event

    }

}

Create interface

interface ActivityNavigation {

    fun startActivityForResult(intent: Intent?, requestCode: Int)

}

** Now it's time to implement! **

In your LoginViewModel

const val GOOGLE_SIGN_IN : Int = 9001



class LoginViewModel @Inject constructor(

    private val loginRepository: LoginRepository,

    private val googleSignInClient: GoogleSignInClient

): ViewModel() {



    val startActivityForResultEvent = LiveMessageEvent<ActivityNavigation>()

    ..



    //Called on google login button click

    fun googleSignUp() {

        val signInIntent = googleSignInClient.signInIntent

        startActivityForResultEvent.sendEvent { startActivityForResult(signInIntent, GOOGLE_SIGN_IN) }

    }



    //Called from Activity receving result

    fun onResultFromActivity(requestCode: Int, resultCode: Int, data: Intent?) {

        when(requestCode) {

            GOOGLE_SIGN_IN -> {

                val task = GoogleSignIn.getSignedInAccountFromIntent(data)

                googleSignInComplete(task)

            }

            ..

        }

    }



    private fun googleSignInComplete(completedTask: Task<GoogleSignInAccount>) {

        try {

            val account = completedTask.getResult(ApiException::class.java)

            account?.apply {

                // .. Store user details

                emitUiState(

                    showSuccess = Event(R.string.login_successful)

                )

            }

        }catch (e: ApiException) {

            emitUiState(

                showError = Event(R.string.login_failed)

            )

        }

    }

In your LoginActivty

//Called from onCreate once the ViewModel is initialized.

private fun subscribeUi() {

        //this sets the LifeCycler owner and receiver

        viewModel.startActivityForResultEvent.setEventReceiver(this, this)

        ..

}



public override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {

        viewModel.onResultFromActivity(requestCode,resultCode,data)

        super.onActivityResult(requestCode, resultCode, data)

}

# Following this approach ensures LoginViewModel acts a link between the view(LoginActivity) and model(GoogleSignInClient) and view is only responsible for displaying the UI events.