Android + Firebase

build.gradle.kts

plugins {
...
    alias(libs.plugins.google.services)
    alias(libs.plugins.ksp)
    alias(libs.plugins.hilt.android)
    alias(libs.plugins.serialization)
}

android {

    defaultConfig {
...
    buildConfigField(
            "String",
            "GOOGLE_CLIENT_ID",
            project.properties["google_client_id"] as String
        )
    }

    buildFeatures {
        compose = true
        buildConfig = true
    }
}

dependencies {
    implementation(libs.dagger.hilt.android)
    ksp(libs.dagger.hilt.android.compiler)
    ksp(libs.androidx.hilt.compiler)
    implementation(libs.androidx.hilt.navigation.compose)

    implementation(platform(libs.androidx.compose.bom))
    implementation(libs.androidx.navigation.compose)
    implementation(libs.kotlinx.serialization.json)

    // firebase
    implementation(platform(libs.firebase.bom))
    implementation(libs.firebase.analytics)
    implementation(libs.firebase.auth.ktx)
    implementation(libs.play.services.auth)
    implementation(libs.androidx.credentials)
    implementation(libs.androidx.credentials.play.services.auth)
    implementation(libs.googleid)
}

EmailSignInViewModel.kt

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.FirebaseUser
import dagger.hilt.android.lifecycle.HiltViewModel
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.launch
import javax.inject.Inject

@HiltViewModel
class EmailSignInViewModel @Inject constructor() : ViewModel() {
    sealed class SignInUIState {
        data object Initial : SignInUIState()
        data object Processing : SignInUIState()
        class Success(val user: FirebaseUser) : SignInUIState()
        data object Canceled : SignInUIState()
        class Failed(e: Exception) : SignInUIState()
    }

    private val _uiState = MutableStateFlow<SignInUIState>(SignInUIState.Initial)
    val uiState = _uiState.asStateFlow()

//    val isProcessingSignIn = uiState.map { it is SignInUIState.Processing }

    /**
     * email と password でサインイン
     */
    fun signIn(email: String, password: String) {
        viewModelScope.launch(Dispatchers.IO) {
            _uiState.value = SignInUIState.Processing

            FirebaseAuth.getInstance().signInWithEmailAndPassword(email, password)
                .addOnSuccessListener { result ->
                    _uiState.value = SignInUIState.Success(result.user!!)
                }.addOnFailureListener { e ->
                    _uiState.value = SignInUIState.Failed(e)
                }.addOnCanceledListener { _uiState.value = SignInUIState.Canceled }
        }
    }
}

GoogleSignInViewModel.kt

import android.app.Application
import androidx.credentials.CredentialManager
import androidx.credentials.CustomCredential
import androidx.credentials.GetCredentialRequest
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.google.android.libraries.identity.googleid.GetSignInWithGoogleOption
import com.google.android.libraries.identity.googleid.GoogleIdTokenCredential
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.FirebaseUser
import com.google.firebase.auth.GoogleAuthProvider
import dagger.hilt.android.lifecycle.HiltViewModel
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.launch
import kotlinx.coroutines.tasks.await
import org.nunocky.myfirebaseapp.BuildConfig
import javax.inject.Inject

/**
 * Google Sign In
 * very thanks to https://qiita.com/kisayama/items/5dc7618b76f6d86a6d55
 */

// TODO implementするライブラリのことを記載する

@HiltViewModel
class GoogleSignInViewModel @Inject constructor(
    private val context: Application
) : ViewModel() {
    sealed class SignInUIState {
        data object Initial : SignInUIState()
        data object Processing : SignInUIState()
        class Success(val user: FirebaseUser) : SignInUIState()
        class Failed(e: Exception) : SignInUIState()
    }

    private val _signInUIState = MutableStateFlow<SignInUIState>(SignInUIState.Initial)
    val signInUIState = _signInUIState.asStateFlow()

    private fun getSignInRequest(): GetCredentialRequest {
        val googleClientId = BuildConfig.GOOGLE_CLIENT_ID

        // Googleサインインリクエストを作成
        val googleIdOption: GetSignInWithGoogleOption = GetSignInWithGoogleOption.Builder(
            googleClientId
        ) // nonceがあれば設定
            .build()

        // GetCredentialRequestを作成
        return GetCredentialRequest.Builder()
            .addCredentialOption(googleIdOption)
            .build()
    }

    fun signIn() {
        viewModelScope.launch {
            try {
                _signInUIState.value = SignInUIState.Processing

                val auth: FirebaseAuth = FirebaseAuth.getInstance()
                val credentialManager = CredentialManager.create(context)

                val request = getSignInRequest()

                val credential = try {
                    val result =
                        credentialManager.getCredential(context = context, request = request)
                    result.credential
                } catch (e: Exception) {
                    throw e
                }

                // 取得した資格情報がGoogle IDトークンであるか確認
                if (credential is CustomCredential && credential.type == GoogleIdTokenCredential.TYPE_GOOGLE_ID_TOKEN_CREDENTIAL) {
                    val googleIdTokenCredential =
                        GoogleIdTokenCredential.createFrom(credential.data)

                    // IDトークンを取得
                    val googleIdToken = googleIdTokenCredential.idToken

                    // Firebaseの認証情報を作成
                    val firebaseCredential = GoogleAuthProvider.getCredential(googleIdToken, null)

                    // Firebaseでサインイン処理を実行
                    val authResult = auth.signInWithCredential(firebaseCredential).await()

                    // サインイン成功時のユーザー情報を取得
                    val firebaseUser = authResult.user

                    if (firebaseUser != null) {
                        _signInUIState.value = SignInUIState.Success(firebaseUser)
                    }
                } else {
                    // アカウント情報が見つからない時の処理
                    _signInUIState.value = SignInUIState.Failed(Exception("account not found"))
                }
            } catch (e: Exception) {
                _signInUIState.value = SignInUIState.Failed(e)
            }
        }
    }
}

libs.versions.toml

[versions]
serialization = "2.1.10"
kotlinxSerializationJson = "1.8.0"
ksp = "2.1.10-1.0.30"
hiltAndroid = "2.55"
hiltAndroidCompiler = "2.55"
hiltCompiler = "1.2.0"
hiltNavigationCompose = "1.2.0"

navigationCompose = "2.8.7"

google-services = "4.4.2"
firebaseBom = "33.9.0"
firebaseAuthKtx = "23.2.0"
playServiceAuth = "21.3.0"
credentials = "1.5.0-rc01"
googleid = "1.1.1"

[libraries]
kotlinx-serialization-json = { module = "org.jetbrains.kotlinx:kotlinx-serialization-json", version.ref = "kotlinxSerializationJson" }
dagger-hilt-android = { module = "com.google.dagger:hilt-android", version.ref = "hiltAndroid" }
dagger-hilt-android-compiler = { module = "com.google.dagger:hilt-android-compiler", version.ref = "hiltAndroidCompiler" }
androidx-hilt-compiler = { module = "androidx.hilt:hilt-compiler", version.ref = "hiltCompiler" }
androidx-hilt-navigation-compose = { module = "androidx.hilt:hilt-navigation-compose", version.ref = "hiltNavigationCompose" }
androidx-navigation-compose = { module = "androidx.navigation:navigation-compose", version.ref = "navigationCompose" }

firebase-bom = { module = "com.google.firebase:firebase-bom", version.ref = "firebaseBom" }
firebase-analytics = { module = "com.google.firebase:firebase-analytics-ktx" }
firebase-auth-ktx = { group = "com.google.firebase", name = "firebase-auth-ktx", version.ref = "firebaseAuthKtx" }
play-services-auth = { module = "com.google.android.gms:play-services-auth", version.ref = "playServiceAuth" }
androidx-credentials = { module = "androidx.credentials:credentials", version.ref = "credentials" }
androidx-credentials-play-services-auth = { module = "androidx.credentials:credentials-play-services-auth", version.ref = "credentials" }
googleid = { module = "com.google.android.libraries.identity.googleid:googleid", version.ref = "googleid" }

[plugins]
kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }
google-services = { id = "com.google.gms.google-services", version.ref = "google-services" }

ksp = { id = "com.google.devtools.ksp", version.ref = "ksp" }
hilt-android = { id = "com.google.dagger.hilt.android", version.ref = "hiltAndroid" }
serialization = { id = "org.jetbrains.kotlin.plugin.serialization", version.ref = "serialization" }

project.build.gradle.kts

// Top-level build file where you can add configuration options common to all sub-projects/modules.
plugins {
    alias(libs.plugins.android.application) apply false
    alias(libs.plugins.kotlin.android) apply false
    alias(libs.plugins.kotlin.compose) apply false

    alias(libs.plugins.google.services) apply false
    alias(libs.plugins.ksp) apply false
    alias(libs.plugins.hilt.android) apply false
    alias(libs.plugins.serialization) apply false
}