ليعمل التطبيق بالخلفيه

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override 

   protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
      

  setContentView(R.layout.activity_main);

        startService(new Intent(this, YourService.class));

    }

import android.app.Service;

import android.content.Intent;
import android.os.IBinder;
import android.support.annotation.Nullable;

public class YourService extends Service {

    @Nullable 

   @Override  

  public IBinder onBind(Intent intent) {
        return null;
    }

    @Override  

  public int onStartCommand(Intent intent, int flags, int startId) {
        // do your jobs here    

    return super.onStartCommand(intent, flags, startId);
    }
}