android - Foreground service getting killed from Oreo

Question

I have written a foreground service which is working properly for all OS version lower than Oreo. From Oreo application process is getting killed after 5 minutes of closing and removing the application from recents.

As per android developer documentation for background execution limitations OS should not kill application for which a foreground service is running and notification is shown in notification window.

As per guidelines on developer documentation. I followed below steps to start foreground-service.

1. Foreground service is started with startForegroundService() method
2. Within 5 sec after starting service a notification is shown for the service using startForeground()
3. Return START_STICKY from onStartCommand() of service

I am facing this issue on following phones:

1. OnePlus 5T
2. Vivo
3. Oppo
4. Mi

What I tried to prevent foreground-service from being destroyed?

1. Disable the battery optimization for the application by showing system dialog to user to disable doze mode.

What I tried to restart the foreground-service?

1. Used AlarmManager to restart the service from onTaskRemoved(). Please check this link for details.

As per my understanding these manufacturers have customized the AOSP and are not respecting the OS guidelines for allowing foreground service to run. May be these manufacturers have done this because of giving long battery life time to users.

Foreground service class

    class DataCaptureService : Service() {

        private var isServiceStarted = false

        override fun onBind(intent: Intent?): IBinder? {
            return null
        }

override fun onCreate() {
        super.onCreate()
        wakeLock = (getSystemService(Context.POWER_SERVICE) as PowerManager).run {
                    newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "WakelockTag123").apply {
                        acquire()
                    }
                }
    }


        override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
            val serviceAction = intent?.action
            LogUtils.logD("OnStartCommand(). Action=$serviceAction")
            if (Constants.INTENT.ACTION_STOP_SERVICE == serviceAction) {
                LogUtils.logD("Stopping data capture service")
                stopForeground(true)
                stopSelf()
            } else if (Constants.INTENT.ACTION_START_SERVICE == serviceAction && !isServiceStarted) {
                LogUtils.logD("Starting data capture service")
                isServiceStarted = true
                // Here showing notification using a utility method (startForeground(id, notification))
                createNotification(this)
                // Doing some stuff here
                ----------------------
                //
            }
            return START_STICKY
        }

        override fun onDestroy() {
            super.onDestroy()
            if (isServiceStarted) {
                LogUtils.logD("onDestroy of DataCaptureService method is invoked")
                // Doing some stuff here
                ----------------------
                //
                isServiceStarted = false
                if (wakeLock.isHeld) {
                    wakeLock.release()
                }
            }
        }

        override fun onTaskRemoved(rootIntent: Intent?) {
            LogUtils.logD("onTaskRemoved of DataCaptureService method is invoked")
            ensureServiceStaysRunning()
            super.onTaskRemoved(rootIntent)
        }

        private fun ensureServiceStaysRunning() {
            val restartAlarmInterval = 60 * 1000
            val resetAlarmTimer = 30 * 1000L
            // From this broadcast I am restarting the service
            val restartIntent = Intent(this, ServiceRestartBroadcast::class.java)
            restartIntent.action = "RestartedViaAlarm"
            restartIntent.flags = Intent.FLAG_RECEIVER_FOREGROUND
            val alarmMgr = getSystemService(Context.ALARM_SERVICE) as AlarmManager
            val restartServiceHandler = @SuppressLint("HandlerLeak")
            object : Handler() {
                override fun handleMessage(msg: Message) {
                    val pendingIntent = PendingIntent.getBroadcast(applicationContext, 87, restartIntent, PendingIntent.FLAG_CANCEL_CURRENT)
                    val timer = System.currentTimeMillis() + restartAlarmInterval
                    val sdkInt = Build.VERSION.SDK_INT
                    if (sdkInt < Build.VERSION_CODES.KITKAT)
                        alarmMgr.set(AlarmManager.RTC_WAKEUP, timer, pendingIntent)
                    else if (Build.VERSION_CODES.KITKAT <= sdkInt && sdkInt < Build.VERSION_CODES.M)
                        alarmMgr.setExact(AlarmManager.RTC_WAKEUP, timer, pendingIntent)
                    else if (sdkInt >= Build.VERSION_CODES.M) {
                        alarmMgr.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, timer, pendingIntent)
                    }
                    sendEmptyMessageDelayed(0, resetAlarmTimer)
                    stopSelf()
                }
            }
            restartServiceHandler.sendEmptyMessageDelayed(0, 0)
        }

    }

Please share your suggestion if you have faced similar type of issue and managed to find a solution for this.

Answer 1

I've analyzed the issue on OnePlus, as I'm in the same situation as you. As I see currently, there is no solution. OnePlus clearly follows a bad practice.

As they haven't released the source code which kills processes in this manner, I downloaded a OnePlus ROM (I choose OnePlus 5T 5.1.5), extract it, find the .class which does this (OnePlusHighPowerDetector.class in services.vdex), decompile it, and tried to find out what's going on.

You can find a version of this class here (it is not by me, and maybe it is not the same version that I've used): https://github.com/joshuous/oneplus_blobs_decompiled/blob/master/com/android/server/am/OnePlusHighPowerDetector.java

Unfortunately, the most important functions aren't decompiled successfully. But we can analyze the bytecode anyway. Here's what I've found:

• OnePlus kills background processes (it seems that it doesn't matter whether it has a foreground service or not) without mercy. Almost all of them. It doesn't really matter, how little CPU resources are used. My app uses less than 1%, and it gets killed.
• If the app is pinned in the recent app list (determined by a list of com_oneplus_systemui_recent_task_lockd_list), it doesn't get killed. So, the user can save the app by pinning it. But it is inconvenient for them.
• Oneplus provides a list of processes, which they don't kill. This list is in oneplus-framework-res.apk/res/values/array.xml, with the key string-array name="backgroundprocess_detection_app_whitelist". This list mostly contains map and fitness applications¹.
• Maybe there are other factors which can save a process being killed, I haven't analyzed the issue further. If you have the time, check out OnePlusHighPowerDetector.java.

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Here are the steps needed to decompile a .vdex file:

• use Vdex Extractor to create a .dex from .vdex (maybe you'll need to use the --ignore-crc-error option)
• use JADX to decompile a .dex (this is currently the best decompiler in my opinion), or use dex2jar to create a .jar from .dex, and use any decompiler to decompile the .jar

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^{1Rant: this shows how bad the current situation is. OnePlus, is this really the solution? You've chosen 10-15 applications, which can run in the background, and you don't care about all the other ones? How can one create a new fitness/map/music player application, which works safely on your device?}