端末がスリープしても動き続けるバックグラウンド処理

HandlerとWakeLockで実現しました。(ソースコードはKotlinで書いています。)

AndroidManifest.xml

<uses-permission android:name="android.permission.WAKE_LOCK" />

 時間を刻むタイマーサービス

TimerService.kt

class TimerService : Service() {

    val handler = Handler()

    companion object {
        private var wakelock : PowerManager.WakeLock? = null
        private var timer : Timer? = null
    }

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

    override fun onCreate() {
        super.onCreate()

        val databaseManager = DatabaseManager()
        databaseManager.openDatabaseAll(applicationContext)

        val myNotification = MyNotification(applicationContext)
        myNotification.displayNotification()

        val powerManager = applicationContext!!.getSystemService(Context.POWER_SERVICE) as PowerManager
        wakelock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "PartialWakelock")
        wakelock!!.acquire()

    }

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        super.onStartCommand(intent, flags, startId)

        var count = 0L
        var timePrevious : Long
        var timeNow = System.currentTimeMillis()
        var timeDifference : Long

        handler.postDelayed(object : Runnable {
            override fun run() {
                OnOffSetter() // タイマー内の処理
                handler.postDelayed(this, 15*1000)

                timePrevious = timeNow
                timeNow = System.currentTimeMillis()
                timeDifference = timeNow - timePrevious
                count++
                Log.i("TimerService", count.toString()+"/"+timeDifference.toString())

            }
        }, 15*1000)

        return START_STICKY
    }

    override fun onDestroy() {
        super.onDestroy()

        handler.removeCallbacksAndMessages(null)

        val myNotification = MyNotification(applicationContext)
        myNotification.cancelNotification()

        if (wakelock != null) {
            wakelock!!.release()
        }

    }
}

 タイマーを起動する処理

val intent = Intent(this, TimerService::class.java)
startService(intent)

stopService(intent)

WakeLockは、バッテリーを消費するので、必要最低限にする必要があります。