后台服务仅在应用程序关闭时激活

Question

奇怪的是，我的服务确实在后台运行，但它只在应用程序关闭时创建警报，而不是在它运行时创建。任何人都可以提供一些有关为什么会发生这种情况的见解。我的服务类如下。

public class TimeDifferenceService extends Service {
DatabaseHelper myDbs;


public boolean notificationCheck;
@Override
public IBinder onBind(Intent intent) {
    return null;
}

@Override
public void onCreate() {
    super.onCreate();
}

@Override
public void onDestroy() {
    super.onDestroy();
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {



    myDbs = new DatabaseHelper(this);
    mHandler.postDelayed(mUpdateTimeChecker,100);
   return START_STICKY;
}
Handler mHandler = new Handler();
final Runnable mUpdateTimeChecker = new Runnable() {
    public void run() {
        // do whatever you want to change here, like:


        Cursor res = myDbs.GetFirstTime();
        if (res.getCount() == 0) {
            return;
        }

        while (res.moveToNext()) {
            String booleancheck =res.getString(5);
            notificationCheck = Boolean.parseBoolean(booleancheck);

            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            TimeZone tz = TimeZone.getDefault();

            Calendar c1 = Calendar.getInstance(tz);
            Calendar c2 = Calendar.getInstance(TimeZone.getTimeZone("UTC"));



            try {
                c1.setTime(sdf.parse(res.getString(1)));
            } catch (ParseException e) {
                e.printStackTrace();
            }


            c2.getTime();
            long timeDiff = ((c1.getTimeInMillis()-c2.getTimeInMillis())/(1000*60));

            if (timeDiff <= 60 && timeDiff >=0 && !notificationCheck){
                setAlarm();
                String notifDisplay = "true";
                update(res.getInt(0),notifDisplay);
            }else {

            }

            res.close();
        }
        mHandler.postDelayed(this,1000);
    }

};
public void setAlarm(){
    long alertTime = new GregorianCalendar().getTimeInMillis()+1*1000;
    Intent alertIntent = new Intent(this,AlertReciever.class);
    AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);

    alarmManager.set(AlarmManager.RTC_WAKEUP,alertTime, PendingIntent.getBroadcast(this,1,alertIntent, PendingIntent.FLAG_UPDATE_CURRENT));

}

}