Android Notification Action — Complete Guide

// Action that opens an Activity instead of inline reply
val replyIntent = Intent(this, ReplyActivity::class.java)
val replyPendingIntent = PendingIntent.getActivity(this, 0, replyIntent, FLAG_IMMUTABLE)

val notification = NotificationCompat.Builder(this, CHANNEL_ID)
    .addAction(R.drawable.ic_reply, "Reply", replyPendingIntent) // Opens new Activity — bad UX
    .build()

class MessagingService : FirebaseMessagingService() {

    private fun showReplyNotification(message: Message) {
        // RemoteInput for inline reply
        val remoteInput = RemoteInput.Builder("reply_key")
            .setLabel("Reply to ${message.sender}")
            .build()

        // Reply intent — handled by a BroadcastReceiver
        val replyIntent = Intent(this, ReplyReceiver::class.java).apply {
            putExtra("message_id", message.id)
            putExtra("sender_id", message.senderId)
        }
        val replyPendingIntent = PendingIntent.getBroadcast(
            this, message.id.hashCode(), replyIntent,
            PendingIntent.FLAG_MUTABLE or PendingIntent.FLAG_UPDATE_CURRENT // Mutable needed for RemoteInput
        )

        // Mark as read action
        val markReadIntent = Intent(this, MarkReadReceiver::class.java).apply {
            putExtra("message_id", message.id)
        }
        val markReadPendingIntent = PendingIntent.getBroadcast(
            this, message.id.hashCode() + 1, markReadIntent, FLAG_IMMUTABLE
        )

        val replyAction = NotificationCompat.Action.Builder(
            R.drawable.ic_reply, "Reply", replyPendingIntent
        )
            .addRemoteInput(remoteInput)
            .setAllowGeneratedReplies(true)
            .build()

        val notification = NotificationCompat.Builder(this, MESSAGES_CHANNEL_ID)
            .setContentTitle(message.sender)
            .setContentText(message.text)
            .setSmallIcon(R.drawable.ic_message)
            .addAction(replyAction)
            .addAction(R.drawable.ic_check, "Mark Read", markReadPendingIntent)
            .build()

        notify(message.id, notification)
    }
}

// BroadcastReceiver for inline reply
class ReplyReceiver : BroadcastReceiver() {
    override fun onReceive(context: Context, intent: Intent) {
        val replyText = RemoteInput.getResultsFromIntent(intent)?.getString("reply_key")
        val messageId = intent.getIntExtra("message_id", -1)

        if (replyText != null) {
            // Send reply via API
            CoroutineScope(Dispatchers.IO).launch {
                api.sendReply(messageId, replyText)
            }
            // Update notification to show sent confirmation
            val updatedNotification = NotificationCompat.Builder(context, MESSAGES_CHANNEL_ID)
                .setContentText("You: $replyText")
                .setSmallIcon(R.drawable.ic_message)
                .build()
            NotificationManagerCompat.from(context).notify(messageId, updatedNotification)
        }
    }
}