Accessing Arraylist<String > from bind service returning empty

Question

I am accessing marraylist variable of service and although it is initialized by data from Firebase but returning empty marraylist in Activity this variable is initialized in service array by fetching data from Firebase database and in toast I am getting fetched data from Firebase to marraylist but when I am trying to access the variable in activity it is returning me empty ArrayList.

My Class that is binded to service is

public class ProfileList extends AppCompatActivity  
  implements View.OnClickListener {
        private FirebaseAuth mAuth;
        Dialog Mydialog;
        private FirebaseAuth.AuthStateListener authStateListener;
        public DatabaseReference db;
        public String userid;
        FirebaseUser firebaseUser;
        public String iamlog="hy";
        List<String> listSt;
        String snapdata,log;
        ArrayList<String> m1arraylist = new ArrayList <String>();
        RecyclerView recyclerView;
        public ProfileService myservice;
        Intent intent;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.profilelist);
            db = FirebaseDatabase.getInstance().getReference().child("users");
            recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
            recyclerView.setLayoutManager(new LinearLayoutManager(this));

            Button button2 = (Button) findViewById(R.id.button2);
            mAuth = FirebaseAuth.getInstance();
            userid = mAuth.getCurrentUser().getUid();
            db = db.child(userid);
            Uri uri = Uri.parse(String.valueOf(db));
            Log.e(iamlog,String.valueOf(uri));

            Intent Profileserviceint = new Intent(this, ProfileService.class);
            Profileserviceint.putExtra("dbrefuri",String.valueOf(uri));
            bindService(Profileserviceint, connection, Context.BIND_AUTO_CREATE);

        }





        ServiceConnection connection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                Localservice localservice = (Localservice) service;
                myservice=localservice.getservice();
                m1arraylist=myservice.getdata();
                recyclerView.setAdapter(new ProgramingAdapter(ProfileList.this,localservice.getservice().marraylist));
                Log.e(iamlog,"Profile calss "+ String.valueOf(localservice.getservice().marraylist));

            }

            @Override
            public void onServiceDisconnected(ComponentName name) {

            }
        };

My service class is

public class ProfileService extends Service {
    public DatabaseReference db;
    Intent intent;
    public String iamlog="hy";
    String dbref;

    public ArrayList<String> marraylist = new ArrayList<>() ;

    public IBinder mbinder = new Localservice();
    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     *
     * Used to name the worker thread, important only for debugging.
     */


    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        dbref  =intent.getStringExtra("dbrefuri");
        return  mbinder;
    }

    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     *
     */


    public     class  Localservice extends Binder
    {
        public   ProfileService getservice()
        {
            return ProfileService.this;
        }
    }

    public  ArrayList<String> getdata()
    {
        db=  FirebaseDatabase.getInstance().getReferenceFromUrl(dbref);
        db.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot dataSnapshot2 : dataSnapshot.getChildren())
                {
                    marraylist.add(dataSnapshot2.getKey());
                }
                Toast toast =  Toast.makeText(ProfileService.this ,String.valueOf(marraylist),Toast.LENGTH_LONG);
                toast.show();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

        return marraylist;
    }

}

Answer 1

When you call getData() It initiates data fetch , but the fetch is not completed yet. The ArrayList returned does not have any items in it yet. Once the data is fetched inside the

onDataChange(DataSnapshot dataSnapshot) 

data is added to the list. The RecyclerView does not see this change.

You need to call

notifyDataSetChanged() 

once the data is loaded. Change your code to some thing like this

public class ProfileService extends Service {
    public DatabaseReference db;
    Intent intent;
    public String iamlog="hy";
    String dbref;
    WeakReference<ProfileServiceCallback> profileServiceCallBackRef;

    public ArrayList<String> marraylist = new ArrayList<>() ;

    public IBinder mbinder = new Localservice();
    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     *
     * Used to name the worker thread, important only for debugging.
     */


    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        dbref  =intent.getStringExtra("dbrefuri");
        return  mbinder;
    }

    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     *
     */


    public     class  Localservice extends Binder
    {
        public   ProfileService getservice()
        {
            return ProfileService.this;
        }

        public void setCallback(ProfileServiceCallBack callback){
             profileServiceCallbackRef = new WeakReference<ProfileServiceCallBack>(callback);
        }
    }
    public static interface ProfileServiceCallBack {
           public void onDataChanged(List<String> data);
    }


    public  void getdata()
    {
        db=  FirebaseDatabase.getInstance().getReferenceFromUrl(dbref);
        db.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot dataSnapshot2 : dataSnapshot.getChildren())
                {
                    marraylist.add(dataSnapshot2.getKey());
                }
                Toast toast =  Toast.makeText(ProfileService.this ,String.valueOf(marraylist),Toast.LENGTH_LONG);
                toast.show();
                if(profileServiceCallbackRef != null){
                   ProfileServiceCallback callback = profileServiceCallbackRef.get();
                   if(callback != null){
                      profileServiceCallback.onDataChanged(mArrayList);
                   }
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
    }

}

Activity

public class ProfileList extends AppCompatActivity  
implements View.OnClickListener,ProfileServiceCallback {
        private FirebaseAuth mAuth;
        Dialog Mydialog;
        private FirebaseAuth.AuthStateListener authStateListener;
        public DatabaseReference db;
        public String userid;
        FirebaseUser firebaseUser;
        public String iamlog="hy";
        List<String> listSt;
        String snapdata,log;
        ArrayList<String> m1arraylist = new ArrayList <String>();
        RecyclerView recyclerView;
        public ProfileService myservice;
        ProgramingAdapter programmingAdapter;
        Intent intent;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.profilelist);
            db = FirebaseDatabase.getInstance().getReference().child("users");
            recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
            recyclerView.setLayoutManager(new LinearLayoutManager(this));
            programmingAdapter = new ProgrammingAdapter();
            recyclerView.setAdapter(programmingAdapter);
            recyclerView.setAdapter();
            Button button2 = (Button) findViewById(R.id.button2);
            mAuth = FirebaseAuth.getInstance();
            userid = mAuth.getCurrentUser().getUid();
            db = db.child(userid);
            Uri uri = Uri.parse(String.valueOf(db));
            Log.e(iamlog,String.valueOf(uri));

            Intent Profileserviceint = new Intent(this, ProfileService.class);
            Profileserviceint.putExtra("dbrefuri",String.valueOf(uri));
            bindService(Profileserviceint, connection, Context.BIND_AUTO_CREATE);

        }

        @Override
        public void onDataChanged(List<String> data){
            programmingAdapter.setData(data);
            programmingAdapter.notifyDatasetChanged(); 
        }

        ServiceConnection connection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                Localservice localservice = (Localservice) service;
                myservice=localservice.getservice();
                myservice.getdata(ProfileList.this);
                myservice.setCallback();
                Log.e(iamlog,"Profile calss "+ String.valueOf(localservice.getservice().marraylist));

            }

            @Override
            public void onServiceDisconnected(ComponentName name) {

            }
        };

You need to add a method in your ProgrammingAdapter

setData(List<String> data){
   this.data = data;
   notifyDatasetChanged(); 
}