refactor(custom): move Firebase calls to ViewModel

auth/app/src/main/java/com/google/firebase/quickstart/auth/kotlin/CustomAuthFragment.kt

@@ -5,31 +5,30 @@ import android.util.Log
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
-import android.widget.Toast
 import androidx.fragment.app.Fragment
-import com.google.firebase.auth.FirebaseAuth
-import com.google.firebase.auth.FirebaseUser
-import com.google.firebase.auth.ktx.auth
-import com.google.firebase.ktx.Firebase
-import com.google.firebase.quickstart.auth.R
+import androidx.fragment.app.viewModels
+import androidx.lifecycle.DefaultLifecycleObserver
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.lifecycleScope
+import androidx.lifecycle.repeatOnLifecycle
 import com.google.firebase.quickstart.auth.databinding.FragmentCustomBinding
+import kotlinx.coroutines.launch
 
 /**
  * Demonstrate Firebase Authentication using a custom minted token. For more information, see:
  * https://firebase.google.com/docs/auth/android/custom-auth
  */
 class CustomAuthFragment : Fragment() {
-
-    private lateinit var auth: FirebaseAuth
-
     private var _binding: FragmentCustomBinding? = null
     private val binding: FragmentCustomBinding
         get() = _binding!!
 
-    private var customToken: String? = null
+    private val viewModel by viewModels<CustomAuthViewModel>()
+
     private lateinit var tokenReceiver: TokenBroadcastReceiver
 
-    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
+    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
         _binding = FragmentCustomBinding.inflate(inflater, container, false)
         return binding.root
     }
@@ -38,76 +37,39 @@ class CustomAuthFragment : Fragment() {
         super.onViewCreated(view, savedInstanceState)
 
         // Button click listeners
-        binding.buttonSignIn.setOnClickListener { startSignIn() }
+        binding.buttonSignIn.setOnClickListener { viewModel.startSignIn() }
 
         // Create token receiver (for demo purposes only)
         tokenReceiver = object : TokenBroadcastReceiver() {
             override fun onNewToken(token: String?) {
                 Log.d(TAG, "onNewToken:$token")
-                setCustomToken(token.toString())
+                viewModel.setCustomToken(token)
             }
         }
 
-        // Initialize Firebase Auth
-        auth = Firebase.auth
-    }
-
-    override fun onStart() {
-        super.onStart()
-        // Check if user is signed in (non-null) and update UI accordingly.
-        val currentUser = auth.currentUser
-        updateUI(currentUser)
-    }
-
-    override fun onResume() {
-        super.onResume()
-        requireActivity().registerReceiver(tokenReceiver, TokenBroadcastReceiver.filter)
-    }
-
-    override fun onPause() {
-        super.onPause()
-        requireActivity().unregisterReceiver(tokenReceiver)
-    }
-
-    private fun startSignIn() {
-        // Initiate sign in with custom token
-        customToken?.let {
-            auth.signInWithCustomToken(it)
-                    .addOnCompleteListener(requireActivity()) { task ->
-                        if (task.isSuccessful) {
-                            // Sign in success, update UI with the signed-in user's information
-                            Log.d(TAG, "signInWithCustomToken:success")
-                            val user = auth.currentUser
-                            updateUI(user)
-                        } else {
-                            // If sign in fails, display a message to the user.
-                            Log.w(TAG, "signInWithCustomToken:failure", task.exception)
-                            Toast.makeText(context, "Authentication failed.",
-                                    Toast.LENGTH_SHORT).show()
-                            updateUI(null)
-                        }
-                    }
-        }
-    }
+        viewLifecycleOwner.lifecycle.addObserver(object : DefaultLifecycleObserver {
+            override fun onResume(owner: LifecycleOwner) {
+                super.onResume(owner)
+                requireActivity().registerReceiver(tokenReceiver, TokenBroadcastReceiver.filter)
+            }
 
-    private fun updateUI(user: FirebaseUser?) {
-        if (user != null) {
-            binding.textSignInStatus.text = getString(R.string.custom_auth_signin_status_user, user.uid)
-        } else {
-            binding.textSignInStatus.text = getString(R.string.custom_auth_signin_status_failed)
+            override fun onPause(owner: LifecycleOwner) {
+                super.onPause(owner)
+                requireActivity().unregisterReceiver(tokenReceiver)
+            }
+        })
+
+        lifecycleScope.launch {
+            viewLifecycleOwner.repeatOnLifecycle(Lifecycle.State.STARTED) {
+                viewModel.uiState.collect { uiState ->
+                    binding.buttonSignIn.isEnabled = uiState.isSignInEnabled
+                    binding.textSignInStatus.text = uiState.signInStatus
+                    binding.textTokenStatus.text = uiState.tokenStatus
+                }
+            }
         }
     }
 
-    private fun setCustomToken(token: String) {
-        customToken = token
-
-        val status = "Token:$customToken"
-
-        // Enable/disable sign-in button and show the token
-        binding.buttonSignIn.isEnabled = true
-        binding.textTokenStatus.text = status
-    }
-
     override fun onDestroyView() {
         super.onDestroyView()
         _binding = null

auth/app/src/main/java/com/google/firebase/quickstart/auth/kotlin/CustomAuthViewModel.kt

@@ -0,0 +1,81 @@
+package com.google.firebase.quickstart.auth.kotlin
+
+import android.util.Log
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.google.firebase.auth.FirebaseAuth
+import com.google.firebase.auth.FirebaseUser
+import com.google.firebase.auth.ktx.auth
+import com.google.firebase.ktx.Firebase
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.tasks.await
+
+class CustomAuthViewModel(
+    private val firebaseAuth: FirebaseAuth = Firebase.auth
+) : ViewModel() {
+    private val _uiState = MutableStateFlow(UiState())
+    val uiState: StateFlow<UiState> = _uiState
+
+    private var customToken: String? = null
+
+    data class UiState(
+        var signInStatus: String = "",
+        var tokenStatus: String = "Token:null",
+        var isSignInEnabled: Boolean = false,
+    )
+
+    init {
+        // Check if user is signed in (non-null) and update UI accordingly.
+        val firebaseUser = firebaseAuth.currentUser
+        updateUiState(firebaseUser)
+    }
+
+    fun setCustomToken(customToken: String?) {
+        this.customToken = customToken
+
+        // Enable/disable sign-in button and show the token
+        _uiState.update { it.copy(isSignInEnabled = true, tokenStatus = "Token:$customToken") }
+    }
+
+    fun startSignIn() {
+        customToken?.let { token ->
+            // Initiate sign in with custom token
+            viewModelScope.launch {
+                try {
+                    val authResult = firebaseAuth.signInWithCustomToken(token).await()
+                    // Sign in success, update UI with the signed-in user's information
+                    Log.d(TAG, "signInWithCustomToken:success")
+                    updateUiState(authResult.user)
+                } catch (e: Exception) {
+                    // If sign in fails, display a message to the user.
+                    Log.w(TAG, "signInWithCustomToken:failure", e)
+                    // TODO(thatfiredev): Show "Authentication failed" snackbar
+                    updateUiState(null)
+                }
+            }
+        }
+    }
+
+    private fun updateUiState(user: FirebaseUser?) {
+        if (user != null) {
+            _uiState.update { currentUiState ->
+                currentUiState.copy(
+                    signInStatus = "User ID: ${user.uid}"
+                )
+            }
+        } else {
+            _uiState.update { currentUiState ->
+                currentUiState.copy(
+                    signInStatus = "Error: sign in failed"
+                )
+            }
+        }
+    }
+
+    companion object {
+        private const val TAG = "CustomAuthViewModel"
+    }
+}