Combining Two Arrays of Model Class Type Firebase

问题:

Hi I am trying to populate recycler view by getting data from two different nodes in firebase. However I am getting two separate listings... one of each node. I want to combine them and show as a single item. My original question is posted here if more files are required to be seen : Populating Recycler View From Nested Queries in Firebase

My Fragement is as follows

// Firebase
fbDatabaseRootNode = FirebaseDatabase.getInstance().getReference();
fbDatabaseRefGroupList = fbDatabaseRootNode.child("groups_list").child(current_user_id);
fbDatabaseRefGroups = fbDatabaseRootNode.child("groups");

fbDatabaseRefGroupList.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

        // Array to Get Group List
        lGroupsList = new ArrayList<>();

        if (dataSnapshot.exists()) {

            // Clear Array to Get Group List
            lGroupsList.clear();

            for (DataSnapshot glSnapshot : dataSnapshot.getChildren()) {

                // Use The Model To Format Array List and Pass It Into It
                GroupsListModel g = glSnapshot.getValue(GroupsListModel.class);

                // Array to Get Group List
                lGroupsList.add(g);

                // Get The Group ID To Get Data From Other Nodes
                String groupID = String.valueOf(glSnapshot.getKey());

                fbDatabaseRefGroups.child(groupID).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                        // Array to Get Group List
                        lGroupsList2 = new ArrayList<>();

                        if (dataSnapshot.exists()) {

                            // Clear Array to Get Group List
                            lGroupsList2.clear();

//                                    String groupName = (String) dataSnapshot.child("group_name").getValue();
//                                    String groupTagLine = (String) dataSnapshot.child("group_tagline").getValue();
//                                    String groupMemberCount = (String) dataSnapshot.child("group_member_count").getValue();

                            // Use The Model To Format Array List and Pass It Into It
                            GroupsListModel g = dataSnapshot.getValue(GroupsListModel.class);

                            // Array to Get Group List
                            lGroupsList2.add(g);

                            // Joining The Arrays To Get One Array
                            lGroupsList.addAll(lGroupsList2);

                        }

                    }

                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });

            }

        }

        aGroupList = new GroupsListAdapter(getContext(), lGroupsList);
        rvGroupList.setAdapter(aGroupList);

    }

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

    }
});

however the problem seems to be that instead of joining the two nodes to show item as one, I am getting two items in the list (first one containing data from lGroupsList and second one from lGroupsList2) they do not seem be joining.

// Joining The Arrays To Get One Array
lGroupsList.addAll(lGroupsList2);