NascentCore · yxzhao6 · Nov 12, 2025
diff --git a/README.md b/README.md
@@ -29,6 +29,30 @@ Once created don't forget to update the:
 - Issues Template (bug report + feature request).
 - Pull Request Template.
 
+## Firebase Push Demo 📬
+
+- Replace `app/google-services.json` with the config generated from your Firebase project (keep the same package name or update `APP_ID` accordingly).
+- Enable Firebase Cloud Messaging in the Firebase console and download a server key for testing pushes.
+- Build and run the sample app; the home screen shows the current FCM registration token and automatically subscribes the device to the `demo` topic.
+- Allow the runtime notification permission on Android 13+ when prompted so foreground demos can surface notifications.
+- Send a notification from the Firebase console to either the displayed token or the `demo` topic, or trigger it manually:
+
+```bash
+curl -X POST https://fcm.googleapis.com/fcm/send \
+  -H "Authorization: key=${FIREBASE_SERVER_KEY}" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "to": "/topics/demo",
+    "notification": {
+      "title": "Hello from FCM",
+      "body": "This push was sent using the legacy HTTP API."
+    },
+    "data": {
+      "message": "You can also handle custom payload data in the demo service."
+    }
+  }'
+```
+
 ## Troubleshooting
 
 For help with issues which you might encounter when using this template, please refer to [TROUBLESHOOTING.md](TROUBLESHOOTING.md)

diff --git a/app/build.gradle.kts b/app/build.gradle.kts
@@ -4,6 +4,7 @@ import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 plugins {
     id("com.android.application")
     kotlin("android")
+    alias(libs.plugins.google.services)
 }
 
 val APP_VERSION_NAME : String by project
@@ -71,8 +72,11 @@ dependencies {
     implementation(projects.libraryKotlin)
 
     implementation(libs.androidx.appcompat)
+    implementation(libs.androidx.activity)
     implementation(libs.androidx.constraint.layout)
     implementation(libs.androidx.core.ktx)
+    implementation(platform(libs.firebase.bom))
+    implementation(libs.firebase.messaging)
 
     testImplementation(libs.junit)
 

diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
@@ -2,10 +2,17 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />
+    <uses-permission
+        android:name="android.permission.POST_NOTIFICATIONS"
+        tools:targetApi="tiramisu" />
+
     <application
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
+        android:defaultNotificationChannelId="@string/firebase_notification_channel_id"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/AppTheme"
@@ -18,6 +25,14 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+
+        <service
+            android:name=".firebase.DemoFirebaseMessagingService"
+            android:exported="false">
+            <intent-filter>
+                <action android:name="com.google.firebase.MESSAGING_EVENT" />
+            </intent-filter>
+        </service>
     </application>
 
 </manifest>
diff --git a/app/src/main/java/com/ncorti/kotlin/template/app/MainActivity.kt b/app/src/main/java/com/ncorti/kotlin/template/app/MainActivity.kt
@@ -1,22 +1,48 @@
 package com.ncorti.kotlin.template.app
 
+import android.Manifest
 import android.content.Intent
+import android.content.pm.PackageManager
+import android.os.Build
 import android.os.Bundle
+import android.util.Log
 import android.view.View
+import androidx.activity.result.ActivityResultLauncher
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
+import com.google.firebase.messaging.FirebaseMessaging
 import com.ncorti.kotlin.template.app.databinding.ActivityMainBinding
+import com.ncorti.kotlin.template.app.firebase.NotificationHelper
 import com.ncorti.kotlin.template.library.FactorialCalculator
 import com.ncorti.kotlin.template.library.android.ToastUtil
 
 class MainActivity : AppCompatActivity() {
 
     private lateinit var binding: ActivityMainBinding
+    private var notificationPermissionLauncher: ActivityResultLauncher<String>? = null
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         binding = ActivityMainBinding.inflate(layoutInflater)
         setContentView(binding.root)
 
+        setupNotificationPermissionLauncher()
+        NotificationHelper.ensureDefaultChannel(this)
+
+        if (isNotificationPermissionGranted()) {
+            fetchFirebaseToken()
+        } else {
+            binding.textFirebaseToken.text = getString(R.string.firebase_token_permission_required)
+            requestNotificationPermissionIfNeeded()
+            fetchFirebaseToken()
+        }
+
+        subscribeToDemoTopic()
+        setupUiListeners()
+    }
+
+    private fun setupUiListeners() {
         binding.buttonCompute.setOnClickListener {
             val message = if (binding.editTextFactorial.text.isNotEmpty()) {
                 val input = binding.editTextFactorial.text.toString().toLong()
@@ -40,4 +66,86 @@ class MainActivity : AppCompatActivity() {
             startActivity(intent)
         }
     }
+
+    private fun setupNotificationPermissionLauncher() {
+        notificationPermissionLauncher =
+            registerForActivityResult(ActivityResultContracts.RequestPermission()) { isGranted ->
+                when {
+                    isGranted -> {
+                        Log.d(TAG, "Notification permission granted")
+                        fetchFirebaseToken()
+                    }
+
+                    shouldShowRequestPermissionRationale(Manifest.permission.POST_NOTIFICATIONS) -> {
+                        binding.textFirebaseToken.text =
+                            getString(R.string.firebase_token_permission_rationale)
+                    }
+
+                    else -> {
+                        binding.textFirebaseToken.text =
+                            getString(R.string.firebase_token_permission_denied)
+                    }
+                }
+            }
+    }
+
+    private fun requestNotificationPermissionIfNeeded() {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU) {
+            return
+        }
+
+        if (isNotificationPermissionGranted()) {
+            return
+        }
+
+        notificationPermissionLauncher?.launch(Manifest.permission.POST_NOTIFICATIONS)
+    }
+
+    private fun isNotificationPermissionGranted(): Boolean {
+        return Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU ||
+            ContextCompat.checkSelfPermission(
+                this,
+                Manifest.permission.POST_NOTIFICATIONS
+            ) == PackageManager.PERMISSION_GRANTED
+    }
+
+    private fun fetchFirebaseToken() {
+        binding.textFirebaseToken.text = getString(R.string.firebase_token_loading)
+        FirebaseMessaging.getInstance().token
+            .addOnCompleteListener { task ->
+                if (!task.isSuccessful) {
+                    val errorMessage =
+                        task.exception?.localizedMessage ?: getString(R.string.firebase_token_error_generic)
+                    binding.textFirebaseToken.text =
+                        getString(R.string.firebase_token_error, errorMessage)
+                    Log.w(TAG, "Fetching FCM registration token failed", task.exception)
+                    return@addOnCompleteListener
+                }
+
+                val token = task.result
+                binding.textFirebaseToken.text = token
+                Log.d(TAG, "FCM registration token: $token")
+            }
+    }
+
+    private fun subscribeToDemoTopic() {
+        FirebaseMessaging.getInstance().subscribeToTopic(DEMO_TOPIC)
+            .addOnCompleteListener { task ->
+                if (task.isSuccessful) {
+                    Log.d(TAG, "Subscribed to '$DEMO_TOPIC' topic for demo pushes.")
+                } else {
+                    Log.w(TAG, "Topic subscription failed", task.exception)
+                }
+            }
+    }
+
+    override fun onNewIntent(intent: Intent?) {
+        super.onNewIntent(intent)
+        setIntent(intent)
+    }
+
+    companion object {
+        private const val TAG = "MainActivity"
+        private const val DEMO_TOPIC = "demo"
+    }
 }
diff --git a/app/src/main/java/com/ncorti/kotlin/template/app/firebase/DemoFirebaseMessagingService.kt b/app/src/main/java/com/ncorti/kotlin/template/app/firebase/DemoFirebaseMessagingService.kt
@@ -0,0 +1,68 @@
+package com.ncorti.kotlin.template.app.firebase
+
+import android.Manifest
+import android.content.pm.PackageManager
+import android.os.Build
+import android.util.Log
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationManagerCompat
+import androidx.core.content.ContextCompat
+import com.google.firebase.messaging.FirebaseMessagingService
+import com.google.firebase.messaging.RemoteMessage
+import com.ncorti.kotlin.template.app.R
+import kotlin.random.Random
+
+class DemoFirebaseMessagingService : FirebaseMessagingService() {
+
+    override fun onMessageReceived(message: RemoteMessage) {
+        super.onMessageReceived(message)
+
+        val channelId = NotificationHelper.ensureDefaultChannel(this)
+
+        val title = message.notification?.title
+            ?: message.data[KEY_TITLE]
+            ?: getString(R.string.firebase_default_notification_title)
+
+        val body = message.notification?.body
+            ?: message.data[KEY_BODY]
+            ?: message.data[KEY_MESSAGE]
+            ?: getString(R.string.firebase_default_notification_body)
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU &&
+            ContextCompat.checkSelfPermission(
+                this,
+                Manifest.permission.POST_NOTIFICATIONS
+            ) != PackageManager.PERMISSION_GRANTED
+        ) {
+            Log.w(TAG, "Notification permission not granted; dropping push message.")
+            return
+        }
+
+        Log.d(TAG, "Message received from ${message.from}: $message")
+
+        val notification = NotificationCompat.Builder(this, channelId)
+            .setSmallIcon(R.drawable.ic_launcher_foreground)
+            .setContentTitle(title)
+            .setContentText(body)
+            .setStyle(NotificationCompat.BigTextStyle().bigText(body))
+            .setAutoCancel(true)
+            .setPriority(NotificationCompat.PRIORITY_HIGH)
+            .build()
+
+        with(NotificationManagerCompat.from(this)) {
+            notify(Random.nextInt(0, Int.MAX_VALUE), notification)
+        }
+    }
+
+    override fun onNewToken(token: String) {
+        super.onNewToken(token)
+        Log.i(TAG, "FCM token refreshed: $token")
+    }
+
+    private companion object {
+        private const val TAG = "DemoFirebaseMessaging"
+        private const val KEY_TITLE = "title"
+        private const val KEY_BODY = "body"
+        private const val KEY_MESSAGE = "message"
+    }
+}
diff --git a/app/src/main/java/com/ncorti/kotlin/template/app/firebase/NotificationHelper.kt b/app/src/main/java/com/ncorti/kotlin/template/app/firebase/NotificationHelper.kt
@@ -0,0 +1,33 @@
+package com.ncorti.kotlin.template.app.firebase
+
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.content.Context
+import android.os.Build
+import androidx.core.content.getSystemService
+import com.ncorti.kotlin.template.app.R
+
+object NotificationHelper {
+
+    fun ensureDefaultChannel(context: Context): String {
+        val channelId = context.getString(R.string.firebase_notification_channel_id)
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            val channelName = context.getString(R.string.firebase_notification_channel_name)
+            val channelDescription =
+                context.getString(R.string.firebase_notification_channel_description)
+
+            val notificationManager: NotificationManager? = context.getSystemService()
+            val channel = NotificationChannel(
+                channelId,
+                channelName,
+                NotificationManager.IMPORTANCE_DEFAULT
+            ).apply {
+                description = channelDescription
+            }
+            notificationManager?.createNotificationChannel(channel)
+        }
+
+        return channelId
+    }
+}
diff --git a/app/src/main/res/layout/activity_main.xml b/app/src/main/res/layout/activity_main.xml
@@ -24,9 +24,32 @@
         android:layout_marginVertical="@dimen/base_grid_size"
         android:text="@string/description"
         android:textAppearance="@style/TextAppearance.AppCompat.Body1"
-        app:layout_constraintBottom_toTopOf="@id/edit_text_factorial"
+        app:layout_constraintBottom_toTopOf="@id/text_firebase_token_label"
         app:layout_constraintStart_toStartOf="parent" />
 
+    <TextView
+        android:id="@+id/text_firebase_token_label"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="@string/firebase_token_label"
+        android:textAppearance="@style/TextAppearance.AppCompat.Caption"
+        app:layout_constraintBottom_toTopOf="@id/text_firebase_token"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/description" />
+
+    <TextView
+        android:id="@+id/text_firebase_token"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="@dimen/base_grid_size"
+        android:textIsSelectable="true"
+        android:textSize="12sp"
+        app:layout_constraintBottom_toTopOf="@id/edit_text_factorial"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@id/text_firebase_token_label"
+        tools:text="Fetching token…" />
+
     <EditText
         android:id="@+id/edit_text_factorial"
         android:layout_width="match_parent"
@@ -37,7 +60,7 @@
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@id/description"
+        app:layout_constraintTop_toBottomOf="@id/text_firebase_token"
         app:layout_constraintTop_toTopOf="parent" />
 
     <TextView

diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
@@ -7,4 +7,16 @@
     <string name="notification_title">The Result is: %s</string>
     <string name="please_enter_a_number">Please Enter a Number</string>
     <string name="compose_version">In Compose</string>
+    <string name="firebase_token_label">FCM registration token</string>
+    <string name="firebase_token_loading">Fetching token…</string>
+    <string name="firebase_token_error">Unable to fetch token (%1$s)</string>
+    <string name="firebase_token_error_generic">unknown error</string>
+    <string name="firebase_token_permission_required">Grant notification permission to preview incoming pushes.</string>
+    <string name="firebase_token_permission_rationale">Enable notifications so we can display Firebase push messages.</string>
+    <string name="firebase_token_permission_denied">Notification permission denied. You can enable it later from system settings.</string>
+    <string name="firebase_notification_channel_id">firebase_demo_channel</string>
+    <string name="firebase_notification_channel_name">Demo push notifications</string>
+    <string name="firebase_notification_channel_description">Shows Firebase Cloud Messaging demo alerts.</string>
+    <string name="firebase_default_notification_title">Firebase demo message</string>
+    <string name="firebase_default_notification_body">Send yourself a push from the Firebase console or REST API to see it here.</string>
 </resources>
diff --git a/build.gradle.kts b/build.gradle.kts
@@ -3,6 +3,7 @@ plugins {
     id("com.android.library") apply false
     kotlin("android") apply false
     alias(libs.plugins.compose.compiler) apply false
+    alias(libs.plugins.google.services) apply false
     alias(libs.plugins.detekt)
     alias(libs.plugins.nexus.publish)
     cleanup