sample implementation of registration tokens for FCM

messaging/app/build.gradle

@@ -70,8 +70,14 @@ dependencies {
 
     implementation 'com.google.firebase:firebase-installations-ktx:17.1.0'
 
+    // Used to store FCM registration tokens
+    implementation 'com.google.firebase:firebase-firestore-ktx:24.1.0'
+
     implementation 'androidx.work:work-runtime:2.7.1'
 
+    // Used for Firestore
+    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.4.0'
+
     // Testing dependencies
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
     androidTestImplementation 'androidx.test:runner:1.5.2'

messaging/app/src/main/java/com/google/firebase/quickstart/fcm/kotlin/MainActivity.kt

@@ -3,6 +3,7 @@ package com.google.firebase.quickstart.fcm.kotlin
 import android.Manifest
 import android.app.NotificationChannel
 import android.app.NotificationManager
+import android.content.Context
 import android.content.pm.PackageManager
 import android.os.Build
 import android.os.Bundle
@@ -11,11 +12,18 @@ import android.widget.Toast
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.appcompat.app.AppCompatActivity
 import androidx.core.content.ContextCompat
-import com.google.android.gms.tasks.OnCompleteListener
+import androidx.lifecycle.lifecycleScope
+import com.google.firebase.Timestamp
+import com.google.firebase.firestore.FieldValue
+import com.google.firebase.firestore.ktx.firestore
 import com.google.firebase.ktx.Firebase
 import com.google.firebase.messaging.ktx.messaging
 import com.google.firebase.quickstart.fcm.R
 import com.google.firebase.quickstart.fcm.databinding.ActivityMainBinding
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.tasks.await
+import java.util.Calendar
+import java.util.Date
 
 class MainActivity : AppCompatActivity() {
 
@@ -80,25 +88,40 @@ class MainActivity : AppCompatActivity() {
         binding.logTokenButton.setOnClickListener {
             // Get token
             // [START log_reg_token]
-            Firebase.messaging.getToken().addOnCompleteListener(OnCompleteListener { task ->
-                if (!task.isSuccessful) {
-                    Log.w(TAG, "Fetching FCM registration token failed", task.exception)
-                    return@OnCompleteListener
-                }
-
+            lifecycleScope.launch {
                 // Get new FCM registration token
-                val token = task.result
+                val token = getAndStoreRegToken()
 
                 // Log and toast
                 val msg = getString(R.string.msg_token_fmt, token)
                 Log.d(TAG, msg)
                 Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
-            })
+            }
             // [END log_reg_token]
         }
 
         Toast.makeText(this, "See README for setup instructions", Toast.LENGTH_SHORT).show()
         askNotificationPermission()
+
+        // In the app’s first Activity
+        val preferences = this.getPreferences(Context.MODE_PRIVATE)
+        val lastRefreshLong = preferences.getLong("lastRefreshDate", -1)
+        lifecycleScope.launch {
+            val c = Calendar.getInstance().apply {
+                time = if (lastRefreshLong == -1L) Date() else Date(lastRefreshLong)
+                add(Calendar.DATE, 30)
+            }
+
+            val today = Date()
+            if (today.after(c.time) || lastRefreshLong == -1L) {
+                // get token and store into Firestore
+                getAndStoreRegToken()
+                // sync device cache time with Firestore just in case
+                val document = Firebase.firestore.collection("refresh").document("refreshDate").get().await()
+                val updatedTime = (document.data!!["lastRefreshDate"] as Timestamp).seconds * 1000
+                preferences.edit().putLong("lastRefreshDate", updatedTime)
+            }
+        }
     }
 
     private fun askNotificationPermission() {
@@ -115,6 +138,20 @@ class MainActivity : AppCompatActivity() {
         }
     }
 
+    private suspend fun getAndStoreRegToken(): String {
+        var token = Firebase.messaging.token.await()
+        // Add token and timestamp to Firestore for this user
+        val deviceToken = hashMapOf(
+            "token" to token,
+            "timestamp" to FieldValue.serverTimestamp(),
+        )
+
+        // Get user ID from Firebase Auth or your own server
+        Firebase.firestore.collection("fcmTokens").document("myuserid")
+            .set(deviceToken).await()
+        return token
+    }
+
     companion object {
 
         private const val TAG = "MainActivity"

messaging/app/src/main/java/com/google/firebase/quickstart/fcm/kotlin/MyFirebaseMessagingService.kt

@@ -11,6 +11,9 @@ import android.util.Log
 import androidx.core.app.NotificationCompat
 import androidx.work.OneTimeWorkRequest
 import androidx.work.WorkManager
+import com.google.firebase.firestore.FieldValue
+import com.google.firebase.firestore.ktx.firestore
+import com.google.firebase.ktx.Firebase
 import com.google.firebase.messaging.FirebaseMessagingService
 import com.google.firebase.messaging.RemoteMessage
 import com.google.firebase.quickstart.fcm.R
@@ -74,7 +77,7 @@ class MyFirebaseMessagingService : FirebaseMessagingService() {
         // If you want to send messages to this application instance or
         // manage this apps subscriptions on the server side, send the
         // FCM registration token to your app server.
-        sendRegistrationToServer(token)
+        sendTokenToServer(token)
     }
     // [END on_new_token]
 
@@ -103,9 +106,17 @@ class MyFirebaseMessagingService : FirebaseMessagingService() {
      *
      * @param token The new token.
      */
-    private fun sendRegistrationToServer(token: String?) {
+    private fun sendTokenToServer(token: String?) {
         // TODO: Implement this method to send token to your app server.
-        Log.d(TAG, "sendRegistrationTokenToServer($token)")
+        // Add token and timestamp to Firestore for this user
+        val deviceToken = hashMapOf(
+            "token" to token,
+            "timestamp" to FieldValue.serverTimestamp(),
+        )
+
+        // Get user ID from Firebase Auth or your own server
+        Firebase.firestore.collection("fcmTokens").document("myuserid")
+            .set(deviceToken)
     }
 
     /**

messaging/functions/index.js

@@ -0,0 +1,41 @@
+'use strict';
+
+const functions = require('firebase-functions');
+const admin = require('firebase-admin');
+
+admin.initializeApp();
+
+const EXPIRATION_TIME = 1000 * 60 * 60 * 24 * 30; // 30 days
+
+/**
+ * Scheduled function that runs once a month. It updates the last refresh date for
+ * tokens so that a client can refresh the token if the last time it did so was
+ * before the refresh date.
+ */
+
+exports.scheduledFunction = functions.pubsub.schedule('0 0 1 * *').onRun((context) => { 
+    admin.firestore().doc('refresh/refreshDate').set({ lastRefreshDate : Date.now() });
+});
+
+/**
+ * Scheduled function that runs once a day. It retrieves all stale tokens then
+ * unsubscribes them from 'topic1' then deletes them.
+ *
+ * Note: topic1 is an example topic here. It is up to the developer to unsubscribe
+ * all topics the token is subscribed to.
+ */
+exports.pruneTokens = functions.pubsub.schedule('every 24 hours').onRun(async (context) => {
+  const staleTokensResult = await admin.firestore().collection('fcmTokens')
+      .where("timestamp", "<", Date.now() - EXPIRATION_TIME)
+      .get();
+
+  const staleTokens = staleTokensResult.docs.map(staleTokenDoc => staleTokenDoc.id);
+
+  await admin.messaging().unsubscribeFromTopic(staleTokens, 'topic1');
+
+  const deletePromises = [];
+  for (const staleTokenDoc of staleTokensResult.docs) {
+      deletePromises.push(staleTokenDoc.ref.delete());
+  }
+  await Promise.all(deletePromises);
+});

messaging/gradle.properties

@@ -15,3 +15,4 @@ org.gradle.jvmargs=-Xmx1536m
 # This option should only be used with decoupled projects. More details, visit
 # http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
 # org.gradle.parallel=true
+android.useAndroidX=true