Cloud Messaging (push notifications) in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

Handling Notification Click Behavior

You have a Firebase push notification that should open MainActivity when clicked. Which option correctly sets the PendingIntent to achieve this behavior?

Android Kotlin

val intent = Intent(this, MainActivity::class.java)
intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
val pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE)

A val pendingIntent = PendingIntent.getService(this, 0, intent, PendingIntent.FLAG_CANCEL_CURRENT or PendingIntent.FLAG_IMMUTABLE)

B val pendingIntent = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_ONE_SHOT or PendingIntent.FLAG_IMMUTABLE)

C val pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE)

D val pendingIntent = PendingIntent.getActivity(this, 0, intent, 0)

💡 Hint

Use PendingIntent.getActivity for opening an activity on notification click.

Only PendingIntent.getActivity creates an intent to open an activity. Flags FLAG_UPDATE_CURRENT and FLAG_IMMUTABLE ensure the intent updates properly and is secure.

🧠 Conceptual

intermediate

Firebase Cloud Messaging Token Purpose

What is the main purpose of the Firebase Cloud Messaging (FCM) registration token in an Android app?

A It uniquely identifies the app instance to receive push notifications.

B It stores the user's login credentials securely.

C It manages the app's local database synchronization.

D It controls the app's UI theme settings remotely.

💡 Hint

Think about how Firebase knows where to send notifications.

The FCM token is a unique ID for each app installation, allowing Firebase to target push notifications to that specific device.

❓ lifecycle

advanced

Handling Notification in Foreground

When your Android app receives a Firebase push notification while in the foreground, which method should you override to handle the message and show a custom notification?

Android Kotlin

class MyFirebaseMessagingService : FirebaseMessagingService() {
  override fun onMessageReceived(remoteMessage: RemoteMessage) {
    // Your code here
  }
}

A Override onCreate(savedInstanceState: Bundle?) in Application class.

B Override onNewIntent(intent: Intent) in MainActivity.

C Override onStartCommand(intent: Intent?, flags: Int, startId: Int) in Service.

D Override onMessageReceived(remoteMessage: RemoteMessage) in FirebaseMessagingService.

💡 Hint

FirebaseMessagingService has a method called when messages arrive.

onMessageReceived is called for messages received while app is in foreground, allowing custom handling and notification display.

📝 Syntax

advanced

Correct Kotlin Syntax for Notification Channel Creation

Which Kotlin code snippet correctly creates a notification channel for Android 8.0+ devices?

A

val channel = NotificationChannel("channel_id", "Channel Name", 5)
val manager = getSystemService(NotificationManager::class.java)
manager.createNotificationChannel(channel)

B

val channel = NotificationChannel("channel_id", "Channel Name", NotificationManager.IMPORTANCE_DEFAULT)
val manager = getSystemService(NotificationManager::class.java)
manager.createNotificationChannel(channel)

C

val channel = NotificationChannel("channel_id", NotificationManager.IMPORTANCE_DEFAULT)
val manager = getSystemService(NotificationManager::class.java)
manager.createNotificationChannel(channel)

D

val channel = NotificationChannel("channel_id", "Channel Name")
val manager = getSystemService(NotificationManager::class.java)
manager.createNotificationChannel(channel)

💡 Hint

NotificationChannel constructor requires id, name, and importance.

The NotificationChannel constructor needs three parameters: id (String), name (String), and importance (int). Option B uses correct parameters and method calls.

🔧 Debug

expert

Debugging Missing Notifications on Android 13+

Your app targets Android 13 and above. Users report they do not receive push notifications. What is the most likely cause?

A The app lacks runtime POST_NOTIFICATIONS permission request.

B Notification channels are not created on Android 13.

C The Firebase token is expired and needs refreshing.

D The app is missing INTERNET permission in manifest.

💡 Hint

Android 13 introduced a new permission for notifications.

Starting Android 13, apps must request POST_NOTIFICATIONS permission at runtime to show notifications. Without it, notifications won't appear.