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How to use Coroutines and Realtime Database For Firebase Authentication in Android

Firebase Authentication offers backend services, easy-to-use SDKs, and ready-to-use UI frameworks for authenticating users to your app. Firebase Realtime Database can be used to store the user details.  Since most Android developers don't wish to write their own backends, all of this makes their job easier.

In Android, while making network calls such as user authentication, sending, or querying data from the Firebase database, you shouldn't perform such tasks on the Main Thread. You should do such tasks on the Background Thread then update the UI accordingly.

Our code appears cleaner with no boilerplate when we use Coroutines to do Firebase operations, making it more legible/clear, and improving app productivity in the long term.

Prerequisites
Coroutines Recap
Create an Android Project
Setting Up the Project
Main Screens
Designing the User Interface
Creating the Model class
Utility Items
Repository Class
ViewModel Class
Registering Activity
Login Activity
Conclusion
References

Prerequisites

To follow along with this tutorial, you will need the following:

Android Studio installed on your computer.
A solid understanding of how to create and run Android apps.
The Kotlin programming language's fundamentals.
Basic knowledge of Kotlin Coroutines.
Knowledge of using Jetpack Components i.e Livedata, ViewModel and the Repository pattern.
An understanding of linking an Android project to Firebase: If not, take a look at this article Firebase Email and Password Authentication.
Understand how to use ViewBinding.

Coroutines recap

Kotlin Coroutines manages long-running operations that if they are run on the main thread, they will block it.

In this article, we are going to use the following features of Coroutines:

withContext - It uses a provided Coroutine context to call the specified suspending block, suspends until it completes, then returns the result. It executes the jobs sequentially rather than concurrently. Keep in mind that withContext is useful when you have a single job running in the background and wish to return to the task's outcome.
await - While an operation is running, the await waits until it completes without necessary blocking the thread.
viewModelScope - Defines a scope that is tied to the ViewModel. Once ViewModel is cleared, the scope will be cancelled.

To get a more understanding of Coroutines check out this article - Introduction to Kotlin Coroutines.

Let's get started. In this tutorial, we will be creating a simple app that has an authentication feature and stores the user's data in the Firebase Realtime database.

Make sure you have linked your project with Firebase and you have enabled ViewBinding.

Step 1 - Create an Android project

Open your Android Studio and create an empty project and give it the name of your choice.

Step 2 - Setting Up the project

In this step, we will do all the necessary setup for our project

In your ap-level build.gradle, add the following dependencies:

def lifecycle_version = "2.4.0-alpha03"
def coroutines_version = "1.3.9"

implementation platform('com.google.firebase:firebase-bom:28.4.1')

// Firebase Realtime Database
implementation 'com.google.firebase:firebase-database-ktx'

// Firebase Auth
implementation 'com.google.firebase:firebase-auth-ktx'

// ViewModel
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"

// Livedata
implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"

// Coroutines
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutines_version"
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-play-services:1.5.1'

Next, we will define the project structure.

Since our app will have several classes, it's good we come up with some directories that will try and separate them.

Right-click the main package and create the following directories: ui, repository, viewmodel, util, and model.

Step 3 - Main Screens

In this step, we will create two activities i.e LoginActivity and RegisterActivity. On the directories that you created, right-click on the ui directory and create these two activities.

Main

Step 4 - Designing the user interface

After creating the two activities, we will then define what their layout should look like.

The activity_register.xml should look as shown below. Feel free to add more fields depending on your use case.

demo

The activity_login.xml should look as shown below:

demo

Step 5 - Creating the model class

Let's define a model class for a user.

data class User(
    val name: String? = "",
    val email: String? = "",
    val phone: String? = ""
)

Step 6 - Utility items

Before we go any further, let's define two items in the util directory.

i). SafeCall function - This inline function will allow us to make safe network requests.

inline fun <T> safeCall(action: () -> Resource<T>): Resource<T> {
    return try {
        action()
    } catch (e: Exception) {
        Resource.Error(e.message ?: "An unknown Error Occurred")
    }
}

ii). Resource class - This sealed class will represent the three states of our network calls, either Loading, Success, or Error

sealed class Resource<T>(val data: T? = null, val message: String? = null) {
    class Success<T>(data: T) : Resource<T>(data)
    class Loading<T>(data: T? = null) : Resource<T>(data)
    class Error<T>(message: String, data: T? = null) : Resource<T>(data, message)
}

Step 7 - Repository class

In this step, we will define our business logic i.e code to register and login users.

In your repository directory, create a class named MainRepository.

First define the following variables:

private val firebaseAuth = FirebaseAuth.getInstance()
private val databaseReference = FirebaseDatabase.getInstance().getReference("users")

Registering a user

Let's create a function that will have the logic to register users and store their details in the Firebase database.

suspend fun createUser(userName: String, userEmailAddress: String, userPhoneNum: String, userLoginPassword: String): Resource<AuthResult> {
    return withContext(Dispatchers.IO) {
        safeCall {
            val registrationResult = firebaseAuth.createUserWithEmailAndPassword(userEmailAddress, userLoginPassword).await()

            val userId = registrationResult.user?.uid!!
            val newUser = User(userName, userEmailAddress, userPhoneNum)
            databaseReference.child(userId).setValue(newUser).await()
            Resource.Success(registrationResult)
        }
    }
}

Explanation

The createUser function is a suspend function that has a return type of AuthResult which is wrapped in the Resource class that we created earlier. Inside this function, we make use of coroutine's withContext and make sure that our coroutine runs in the Dispatchers.IO.

We then use the inline function - safeCall that we created in the util directory.

Inside the inline function:

We invoke firebaseAuth.createUserWithEmailAndPassword(email, password) and make sure we add the await() at the end. The result of the execution is stored in the variable result.
Next, we extract the uid of the newly created user and then create an object of the class User with all the respective arguments.
We then invoke databaseReference.child(uid).setValue(user).await() to store the user in Firebase Realtime database.
Lastly, we return a successful result.

Logging in a User

We also define another suspeding function for logging in a user:

suspend fun login(email: String, password: String): Resource<AuthResult> {
    return withContext(Dispatchers.IO) {
        safeCall {
            val result = firebaseAuth.signInWithEmailAndPassword(email, password).await()
            Resource.Success(result)
        }
    }
}

Explanation

Similar to the register function, in the login function we make sure that we add the await() at the end of firebaseAuth.signInWithEmailAndPassword(email, password).

Step 8 - ViewModel class

Once you are done working on the MainRepository, right-click on the viewmodel directory and create a new class called MainViewModel.

Inside the ViewModel we will define some variables to represent the status of creating and logging in a user and also an instance of our Repository.

private val _userRegistrationStatus = MutableLiveData<Resource<AuthResult>>()
val userRegistrationStatus: LiveData<Resource<AuthResult>> = _userRegistrationStatus

private val _userSignUpStatus = MutableLiveData<Resource<AuthResult>>()
val userSignUpStatus: LiveData<Resource<AuthResult>> = _userSignUpStatus

private val mainRepository = MainRepository()

We then define two functions corresponding to login and register functions as defined in the Repository.

fun createUser(userName: String, userEmailAddress: String, userPhoneNum: String, userLoginPassword: String) {
    var error =
        if (userEmailAddress.isEmpty() || userName.isEmpty() || userLoginPassword.isEmpty() || userPhoneNum.isEmpty()) {
            "Empty Strings"
        } else if (!Patterns.EMAIL_ADDRESS.matcher(userEmailAddress).matches()) {
            "Not a valid Email"
        } else null

    error?.let {
        _userRegistrationStatus.postValue(Resource.Error(it))
        return
    }
    _userRegistrationStatus.postValue(Resource.Loading())

    viewModelScope.launch(Dispatchers.Main) {
        val registerResult = mainRepository.createUser(userName = userName, userEmailAddress = userEmailAddress, userPhoneNum = userPhoneNum, userLoginPassword = userLoginPassword)
        _userRegistrationStatus.postValue(registerResult)
    }
}

fun signInUser(userEmailAddress: String, userLoginPassword: String) {
    if (userEmailAddress.isEmpty() || userLoginPassword.isEmpty()) {
        _userSignUpStatus.postValue(Resource.Error("Empty Strings"))
    } else {
        _userSignUpStatus.postValue(Resource.Loading())
        viewModelScope.launch(Dispatchers.Main) {
            val loginResult = mainRepository.login(userEmailAddress, userLoginPassword)
            _userSignUpStatus.postValue(loginResult)
        }
    }
}

Explanation

In both functions, we call the Repository functions inside a viewModelScope and make sure we use Dispatchers.Main in the launch function.

Step 9 - Registering activity

Once a user clicks on the register button, we call the registerUser function in the ViewModel passing the necessary parameters. We also observe the status of login as either loading, error, or success.

binding.userRegisterButton.setOnClickListener {
    // the ids might differ based on how you've named your views
    viewModel.createUser(
        binding.edxtUserName.editText?.text.toString(),
        binding.edxtEmailAddress.editText?.text.toString(),
        binding.edxtPhoneNum.editText?.text.toString(),
        binding.edxtPassword.editText?.text.toString()
    )
}

Also, we will define an observer to observe the state of the registration:

viewModel.registerStatus.observe(this, Observer {
    when (it) {
        is Resource.Loading -> {
            binding.registerProgress.isVisible = true
        }
        is Resource.Success -> {
            binding.registerProgress.isVisible = false
            Toast.makeText(applicationContext, "Registered Successfully", Toast.LENGTH_SHORT).show()
        }
        is Resource.Error -> {
            binding.registerProgress.isVisible = false
            Toast.makeText(applicationContext, it.message, Toast.LENGTH_SHORT).show()
        }
    }
})

Once a user clicks on the login button, we call the loginUser function in the ViewModel passing the necessary parameters. We also observe the status of login as either loading, error, or success.

binding.buttonLogin.setOnClickListener {
    viewModel.loginUser(
        binding.editTextLoginEmail.editText?.text.toString(),
        binding.editTextLoginPass.editText?.text.toString()
    )
}

Also, we will define an observer to observe the state of login:

viewModel.loginStatus.observe(this, Observer {
        when (it) {
            is Resource.Loading -> {
                binding.loginProgressBar.isVisible = true
            }
            is Resource.Success -> {
                binding.loginProgressBar.isVisible = false
                Toast.makeText(applicationContext, "Logged In Successfully", Toast.LENGTH_SHORT).show()
            }
            is Resource.Error -> {
                binding.loginProgressBar.isVisible = false
                Toast.makeText(applicationContext, it.message, Toast.LENGTH_SHORT).show()
            }
        }
})

Conclusion

In this tutorial, we have learned how to run Firebase functions in the background thread with Coroutines. To see the full implementation of this tutorial, feel free to check out this Github repository Firebase Coroutines Demo.

Happy learning!