[FIXED] How to handle Flow Coroutines Asynchronous Behaviour while using API

Issue

I am trying to get The liveStatus of authStateListener using Flow Coroutines .But everytime it returns False. Below is the code with which I tried to implement the following.It follows the MVVM pattern.

Code -> FirebaseUserFlow

open class FirebaseUserFlow() {

    private val firebaseAuth = FirebaseAuth.getInstance()

    private var auth: FirebaseUser? = null


    @ExperimentalCoroutinesApi
    fun getUserInfo(): Flow<FirebaseUser?> =
        callbackFlow {
            val authStateListener = FirebaseAuth.AuthStateListener {
                auth = it.currentUser
            }
            offer(auth)
            firebaseAuth.addAuthStateListener(authStateListener)
            awaitClose {
                firebaseAuth.removeAuthStateListener(authStateListener)
            }
        }

}

ViewModel

class AuthViewModel : ViewModel() {


    enum class AuthenticationClass {
        AUTHENTICATED,
        UNAUTHENTICATED
    }

    @ExperimentalCoroutinesApi
    val authenticationState = FirebaseUserFlow().getUserInfo().map {
        Log.d("Tag","The value of the user is $it")
        if (it != null) {
            AuthenticationClass.AUTHENTICATED
        } else {
            AuthenticationClass.UNAUTHENTICATED
        }
    }.asLiveData()


}

The log above always returns false

Fragment

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)

            viewModel.authenticationState.observe(viewLifecycleOwner, Observer {authenticationstate ->
                when (authenticationstate) {

                    AuthViewModel.AuthenticationClass.AUTHENTICATED -> {
                        findNavController().navigate(R.id.action_loginFragmentUser_to_homeFragment)

                        Log.d("TAG","Authenticated")
                    }
                    else ->    Log.d("TAG","Else")

                }

        })

    }

In the above fragment , In the onActivityCreated the liveData is observed and based on the state it navigates to the Home Fragment .

Solution

Your error is here

FirebaseAuth.AuthStateListener {
    auth = it.currentUser
}
trySendBlocking(auth)

You should call offer() inside the callback.

open class FirebaseUserFlow() {

    private val firebaseAuth = FirebaseAuth.getInstance()

    @ExperimentalCoroutinesApi
    fun getUserInfo(): Flow<FirebaseUser?> =
        callbackFlow {
            val authStateListener = FirebaseAuth.AuthStateListener {
                trySendBlocking(it.currentUser)
            }
            firebaseAuth.addAuthStateListener(authStateListener)
            awaitClose {
                firebaseAuth.removeAuthStateListener(authStateListener)
            }
        }

}

Answered By - Sinner of the System
Answer Checked By - Terry (JavaFixing Volunteer)