Recycleview delete data - display data problem

Question

I have one question, I have a recycle view and inside it, I have some items that come from firebase database, when I press the button to delete the item, the item disappears from the dataset but the recycle view is displaying me the item that stands below the item that I just deleted and I don't understand why since I checked stack overflow on how to do it and I did the same thing but it's not working.

I will add 3 photos and the code to explain myself better.

1. First photo: The shopping list: I press on the ADD button, I added two items to the CHART. 2 Second photo: I click on the delete button so I remove that item from the database but now it comes the problem the item below the item I just deleted appears in 2 places now : in the first place and in the second place, it's just like having 2 times the same item but is not true because if I go back to the shopping list and then I come back to the chart now everything is ok and I don't have the same item twice.

Can anyone explain what's going on ?? I think it is a problem with the refresh of the recycle view but not sure 100%.

Code:

   public class CartActivity extends AppCompatActivity implements  OnRemoveItemClickListener{

    private TextView total;
    private ImageButton removeFromCartt;
    private Button pay;
    private RecyclerView mResultList2;
    private DatabaseReference mUserDatabase;
    int i=0;
    int Totalprice=0;
    private UsersAdapter adapter;
    private ArrayList<Users_get> array_data = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cart);
        mUserDatabase = FirebaseDatabase.getInstance().getReference("Cart");

        total          = findViewById(R.id.TotalPrice);
        removeFromCartt = findViewById(R.id.removeFromCart);
        mResultList2    = findViewById(R.id.cartList);
        pay            = findViewById(R.id.pay);

        mResultList2.setHasFixedSize(true);
        mResultList2.setLayoutManager(new LinearLayoutManager(this));


        // Attach a listener to read the data at our posts reference
        mUserDatabase.addValueEventListener(new ValueEventListener() {


            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                int flag=1;
                for(DataSnapshot childSnapshot : dataSnapshot.getChildren()) {
                    Users_get post = childSnapshot.getValue(Users_get.class);
                    array_data.add(new Users_get(post.getName(),post.getSurname(),post.getPrice(),childSnapshot.getKey()));
                    getTotalPrice(post.getPrice(),flag);
                }
                setAdapter();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                System.out.println("The read failed: " + databaseError.getCode());
            }

        });
    }

    private void setAdapter() {
        adapter = new UsersAdapter(array_data,CartActivity.this);
        mResultList2.setAdapter(adapter);
    }

    public int getTotalPrice(Long price,int flag){
        if (array_data != null) {
            if(flag==1)
            {
                Totalprice+=price;
            }
            else
                {
                  Totalprice-=price;
                }
        }
        System.out.println(Totalprice);
        return Totalprice;
    }


    @Override
    public void onRemoveItemClicked(final int position) {
        int flag=0;
        FirebaseDatabase.getInstance().getReference("Cart").child(array_data.get(position).getKey()).removeValue();
        getTotalPrice(array_data.get(position).getPrice(),flag);
        array_data.remove(position);
        adapter.notifyItemRemoved(position);
    }


    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(adapter !=null){
            adapter.removeListener();
        }
    }
}

Answer 1

Try this, When you are deleting item, firebase notify again and the same set of data gets appended to the same array_data list.

@Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                if (adapter == null) {
                    for (DataSnapshot childSnapshot : dataSnapshot.getChildren()) {
                        Users_get post = childSnapshot.getValue(Users_get.class);
                        array_data.add(new Users_get(post.getName(), post.getSurname(), post.getPrice(), childSnapshot.getKey()));
                        getTotalPrice(post.getPrice());
                    }
                    setAdapter();
                } else {
                    adapter.notifyDataSetChanged();
                }
            }