How can I handle storing Firebase notifications for offline access in my chat app?

I’m currently working on implementing a chat application using Firebase Cloud Messaging and facing difficulties architecting it to handle offline scenarios.

Here’s what I aim to achieve: When my app is closed or not running (even in the background) and the internet connection is off, upon receiving a new notification from a sender, I want to cache or store it in the database. Later, when I open my app without an internet connection, I should be able to see all the received messages.

Here’s what I’ve implemented so far:

MyFirebaseMessagingService.kt

val TAG = "FSNotifi"
private val PREFS_NAME = "MyPrefsFile"

class MyFirebaseMessagingService : FirebaseMessagingService() {
    override fun onMessageReceived(remoteMessage: RemoteMessage) {
        val prefs: SharedPreferences = getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
        val editor: SharedPreferences.Editor = prefs.edit()

        // Check if message contains a notification payload.
        remoteMessage.notification?.let {
            editor.putString("FSNoti", it.body.toString())
            editor.apply()
            Log.d(TAG, "Message Notification Body: ${it.body}")
        }
    }
}

AndroidManifest.xml

<service
    android:name=".MyFirebaseMessagingService"
    android:exported="false">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT" />
    </intent-filter>
</service>

Despite this setup, the message doesn’t seem to be stored in SharedPreferences. I’m seeking guidance on how to properly achieve this task. Is there a better approach or a step I might be missing in implementing this offline message storage functionality using Firebase Cloud Messaging?

Any help or advice would be greatly appreciated. Thank you!

PS: I found answer of my question

Userful Link: How to handle notification when app in background in Firebase