How to release service start/stop when Activity is minimized/expanded?

Question

Android

There is an activity in which calculations are constantly made. It is necessary that when the application is minimized, these calculations continue.
Can you please tell me how to implement the launch of the service and passing parameters to it for calculations when the Activity is minimized, and stopping the service and receiving data from it when the Activity is expanded?
I'm attaching a complete listing of what I've got.
MainActivity

package com.example.service;

import android.app.ActivityManager;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.os.IBinder;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;


public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    public String LOG_TAG = "llog";
    Button btn1, btn2, btnexit;
    TextView rezultat;
    private Intent serviceintent;
    private SharedPreferences sPref;
    private ServiceConnection sConn;
    private KVService kvService;
    boolean bound = false, exit = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(LOG_TAG, "onCreate");
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        btn1 = (Button)findViewById(R.id.btn1);
        btn2 = (Button)findViewById(R.id.btn2);
        btnexit = (Button)findViewById(R.id.btnEXIT);
        rezultat = (TextView)findViewById(R.id.rezultat);

        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);
        btnexit.setOnClickListener(this);

        serviceintent = new Intent(this, KVService.class);
        sPref = getSharedPreferences("Rally", Context.MODE_PRIVATE);
        startService(serviceintent);
        sConn = new ServiceConnection() {
            public void onServiceConnected(ComponentName name, IBinder binder) {
                Log.d(LOG_TAG, "KVFragment onServiceConnected");
                kvService = ((KVService.MyBinder) binder).getService();
                bound = true;
            }

            public void onServiceDisconnected(ComponentName name) {
                Log.d(LOG_TAG, "KVFragment onServiceDisconnected");
                rezultat.setText(sPref.getString("KV_Pdistance", ""));
                bound = false;
            }
        };
    }

    @Override
    protected void onResume() {
        Log.d(LOG_TAG, "KVFragment onResume");
        if (bound){
            Log.d(LOG_TAG, "Останавливем сервис");
            //stopService(serviceintent);
            unbindService(sConn);
        };
        //unbindService(sConn);
        super.onResume();
    }

    @Override
    protected void onPause() {
        Log.d(LOG_TAG, "KVFragment onPause");
        super.onPause();
    }

    @Override
    protected void onStop() {
        Log.d(LOG_TAG, "KVFragment onStop");
        if (!exit & !bound) {
            SharedPreferences.Editor ed = sPref.edit();
            ed.putString("KV_Pdistance", "1");
            ed.putString("FakeSpeed", "120.0");
            ed.putString("koef", "1");
            ed.apply();
            Log.d(LOG_TAG, "Вызываем bindservice");
            bindService(serviceintent, sConn, 0);
        }
        super.onStop();
    }

    @Override
    protected void onDestroy() {
        Log.d(LOG_TAG, "KVFragment onDestroy");
        super.onDestroy();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btn1:
                break;
            case R.id.btn2:
                break;
            case R.id.btnEXIT:
                exit =true;
                stopService(serviceintent);
                finish();
                break;
        }
    }

    private boolean isMyServiceRunning(Class<?> serviceClass) {
        ActivityManager manager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
        for (ActivityManager.RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) {
            if (serviceClass.getName().equals(service.service.getClassName())) {
                return true;
            }
        }
        return false;
    }
}

KVService

package com.example.service;

import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;
import android.view.View;

import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class KVService extends Service {
    final String LOG_TAG = "llog";
    Timer myTimer, StartTimer, RealTimer;
    ExecutorService es;
    MyBinder binder = new MyBinder();
    BroadcastReceiver br;
    public Double gpsSpeed = 0.0; //spped
    public final static String GpsSpeed = "0";
    public final static String BROADCAST_ACTION = "KVService";//gpsService
    String NMEA_Speed = "0.0";
    SharedPreferences sPref;
    private double rdist;
    private String fakespped;
    private Double changetime = 10.0;

    public void onCreate() {
        super.onCreate();
        Log.d(LOG_TAG, "KVService onCreate");
        es = Executors.newFixedThreadPool(2);
        sPref = getSharedPreferences("Rally", Context.MODE_PRIVATE);

    }

    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(LOG_TAG, "KVService onStartCommand");
        return super.onStartCommand(intent, flags, startId);
    }

    public void onDestroy() {
        super.onDestroy();
        Log.d(LOG_TAG, "KVService onDestroy");
    }

    class RealTime implements Runnable {

        public RealTime(){
        }

        @Override
        public void run() {
            //Log.i(LOG_TAG, "i = " + i++);
            Log.i(LOG_TAG, "Скорость получена от сервиса GPSService = " + gpsSpeed);

                gpsSpeed = Double.valueOf(fakespped);

            rdist += ((gpsSpeed * (changetime / 36000)) / 100) * Double.valueOf(sPref.getString("koef", ""));//Фактически пройденное расстояние

;
        }
    }

    public IBinder onBind(Intent arg0) {
        Log.d(LOG_TAG, "KVService onBind");
        final RealTime realtime = new RealTime();
        rdist = Double.valueOf(sPref.getString("KV_Pdistance", ""));
        fakespped = sPref.getString("FakeSpeed","");
        RealTimer = new Timer();
        RealTimer.schedule(new TimerTask() {
            public void run() {
                es.execute(realtime);
            }
        }, 0, 10); // каждую 1 секунду
        return binder;
    }
    public boolean onUnbind(Intent intent) {
        Log.d(LOG_TAG, "KVService onUnbind");
        RealTimer.cancel();
        SharedPreferences.Editor ed = sPref.edit();
        ed.putString("KV_Pdistance", String.valueOf(rdist));
        ed.apply();
        return super.onUnbind(intent);
    }

    public class MyBinder extends Binder {
        public KVService getService() {
            return KVService.this;
        }
    }
}

Answer 1

folding/expanding here
passing parameters to the service via Intent or Binder

Answer 2

In your case, as for me, it's best to transfer all the calculation logic to a service and use it as a Bound Service ( developer.android.com/intl/ru/guide/components/bou...
When the user opens the Activity, you raise the service ( startService) passing it initial data and the service starts doing something important :). Next, in the onStart of your Activity, you connect to the service via bindService and start talking to it. When the user minimizes the application, in onStop, you unbind the service via unbindService. But the service continues to do something important) Then when the user returns to your application, you connect to the service and request fresh data.
If you need the system not to kill the service for a long time, use the Foreground Service, this will increase the priority of your process.