android background push -> intent-filter click_action not working

did you create a service named FirebaseMessagingService or similarly named? if you have created it, you need to create intent and PendingIntent there and add it. If you do not have such a service, you need to prepare the service. While researching for you, I found a convenient example; https://www.geeksforgeeks.org/how-to-push-notification-in-android-using-firebase-cloud-messaging/

FirevaseMessagingService.kt source file

remoteMessage.notification?.let { notification ->
            Log.d(CONST.LOG_DEBUG, "click action ${notification.clickAction}")
            if(!notification.title.isNullOrEmpty()) {
                val pattern = longArrayOf(100, 500, 100, 500, 100, 700)
                var intent = Intent(this@MyFirebaseMessagingService, MainActivity::class.java)
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
                intent.putExtra("badge_count", 1)
                //intent.putExtra("scheme", remoteMessage.data["scheme"])

                if(remoteMessage.data != null) {
                    val scheme = remoteMessage.data["scheme"]
                    scheme?.let {
                        if(it.startsWith("WEBVIEW")) {
                            val url = it.split("_")[1]
                            intent = Intent(this@MyFirebaseMessagingService, MainActivity::class.java)
                            intent.putExtra("url", url)
                            intent.putExtra("scheme", it)
                        } else if(it.startsWith("TECHPOST")) {
                            val id = it.split("_")[1]
                            intent = Intent(this@MyFirebaseMessagingService, TechPostDetailActivity::class.java)
                            intent.putExtra("id", id)
                            intent.putExtra("scheme", it)
                        } else if(it.startsWith("HOTCLIP")) {
                            val id = it.split("_")[1]
                            intent = Intent(this@MyFirebaseMessagingService, HotClipDetailActivity::class.java)
                            intent.putExtra("id", id)
                            intent.putExtra("scheme", it)
                        } else if(it.startsWith("NOTICE")) {
                            val id = it.split("_")[1]
                            intent = Intent(this@MyFirebaseMessagingService, NotificationDetailActivity::class.java)
                            intent.putExtra("id", id)
                            intent.putExtra("scheme", it)
                        } else {

                        }
                    }
                }
                val mPendingIntent = if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE)
                } else {
                    PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT)
                }

                var builder = NotificationCompat.Builder(this , "default")
                builder.setFullScreenIntent(mPendingIntent , true)
                builder.setSmallIcon(R.mipmap.appicon)
                builder.setContentTitle(remoteMessage.notification?.title)
                builder.setContentText(remoteMessage.notification?.body)
                //builder.setColor(Color.BLUE)
                builder.setAutoCancel(true)
                builder.setContentIntent(mPendingIntent)
                builder.setVibrate(pattern)

                val notificationManager: NotificationManager = this.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                    notificationManager.createNotificationChannel(NotificationChannel("default" , "default_channel" , NotificationManager.IMPORTANCE_DEFAULT))
                }
                notificationManager.notify(1 , builder.build())
            }
        }

I examined the codes and there are 2 types of messages in Google Firebase Messaging, one of them is "notification" and the other is "data" and you have done data control on the code. How do you send the notification when you send it? Notification can be sent through the firebase panel, but the data message is sent only through the server. When sending a message, you need to check which of the "Notification" - "Data" you are sending. In the "Notification" notifications, the codes you wrote while the application is in the kill state will not work, but if you send a "Data" notification, the codes you wrote when the application is killed will also work. Therefore, if the notification you sent is "Notification", you need to change it to "Data". As I said, "Data" Notifications cannot be sent through the Panel, they are only sent from the server.