override fun onCreate()

in messaging/app/src/main/java/com/google/firebase/quickstart/fcm/kotlin/MainActivity.kt [18:85]
43 lines of code
5 McCabe index (conditional complexity)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            // Create channel to show notifications.
            val channelId = getString(R.string.default_notification_channel_id)
            val channelName = getString(R.string.default_notification_channel_name)
            val notificationManager = getSystemService(NotificationManager::class.java)
            notificationManager?.createNotificationChannel(NotificationChannel(channelId,
                    channelName, NotificationManager.IMPORTANCE_LOW))
        }

        // If a notification message is tapped, any data accompanying the notification
        // message is available in the intent extras. In this sample the launcher
        // intent is fired when the notification is tapped, so any accompanying data would
        // be handled here. If you want a different intent fired, set the click_action
        // field of the notification message to the desired intent. The launcher intent
        // is used when no click_action is specified.
        //
        // Handle possible data accompanying notification message.
        // [START handle_data_extras]
        intent.extras?.let {
            for (key in it.keySet()) {
                val value = intent.extras?.get(key)
                Log.d(TAG, "Key: $key Value: $value")
            }
        }
        // [END handle_data_extras]

        binding.subscribeButton.setOnClickListener {
            Log.d(TAG, "Subscribing to weather topic")
            // [START subscribe_topics]
            Firebase.messaging.subscribeToTopic("weather")
                    .addOnCompleteListener { task ->
                        var msg = getString(R.string.msg_subscribed)
                        if (!task.isSuccessful) {
                            msg = getString(R.string.msg_subscribe_failed)
                        }
                        Log.d(TAG, msg)
                        Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
                    }
            // [END subscribe_topics]
        }

        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
                }

                // Get new FCM registration token
                val token = task.result

                // 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()
    }