Argthtjtr

I have a chat activity that loads the 5 most recent messages of a chat room in descending order from the bottom to the top of a reversed RecyclerView using a Firebase query. Messages sent to the Firebase collection after those messages are loaded are displayed at the bottom of the screen by changing the position new list items are inserted into the list after the onEvent is called. Here is my code:

private void initRecyclerView() {



        //initializes and sets adapter/resets variables





        mAdapter = new ChatRecyclerViewAdapter(mMessages);

        mRecyclerView.setAdapter(mAdapter);

        firstEventListenerCalled = false;





            final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);

            linearLayoutManager.setReverseLayout(true);

            mRecyclerView.setLayoutManager(linearLayoutManager);





            Query query = mCollection.orderBy("timestamp", Query.Direction.DESCENDING).limit(5;



            firstRegistration = query.addSnapshotListener(new EventListener<QuerySnapshot>() {

                @Override

                public void onEvent(@Nullable QuerySnapshot queryDocumentSnapshots, @Nullable FirebaseFirestoreException e) {

                    Log.d("First SnapshotListener", "Called");



                    for (DocumentChange documentChange : queryDocumentSnapshots.getDocumentChanges()) {

                        switch (documentChange.getType()) {

                            case ADDED:



                                //Creates listener for queried messages that puts messages retrieved during initial query at end of message list,

                                // then another one after one runs its course that puts new ones at the beginning of the list

                                if (!firstEventListenerCalled) {



                                    Message message = documentChange.getDocument().toObject(Message.class);



                                    mMessages.add(message);



                                    mAdapter.notifyDataSetChanged();



                                } else if (firstEventListenerCalled) {



                                    Message message = documentChange.getDocument().toObject(Message.class);

                                    mMessages.add(0, message);

                                    mAdapter.notifyDataSetChanged();

                                    Log.d(TAG, "newMessageAdded " + message.getMessage());

                                }





                        }

                    }



                    firstEventListenerCalled = true;



                }

            });

I am attempting to remove the ListenerRegistration in the activity's onStop() method, clear the contents of the RecyclerView in the onRestart() method, and then re-call the method above in onStart(), so that no messages come in when the activity is stopped and that any messages sent during that time appear among the 5 queried by the initRecyclerView() method when the activity is restarted:

@Override

    protected void onRestart() {

        super.onRestart();

        mMessages.clear();

        mAdapter.notifyItemRangeRemoved(0, mMessages.size());

    }



    @Override

    protected void onStart() {

        super.onStart();

        Log.d(TAG, "onStart Called");

        initRecyclerView();



    }



    @Override

    protected void onStop() {

        super.onStop();

        Log.d(TAG, "onStop Called");

        firstRegistration.remove();



        if (refreshRegistraton != null) {

            refreshRegistraton.remove();

        }

    }



    @Override

    public void onBackPressed() {

        finish();



    }

However, the following happens when the activity is restarted using this strategy:

1. The 5 queried messages appear in the proper order


2. 
   

   Any messages sent while the activity was stopped appear in addition to those 5 messages and in reverse order:

   
   
   
   
   

   • Old message 1

   
   

   • Old message 2

   
   

   • Old message 3

   
   

   • Old message 4

   
   

   • Old message 5

   
   

   • Message sent while stopped 2

   
   

   • Message sent while stopped 1

   
   
   
   

The new messages appear to be getting loaded in the order described for when firstEventListenerCalled == true, but it is made false at the beginning of the initRecyclerView() method every time it is called. They should not be getting loaded separately at all since I removed the listeners and totally recreated the RecyclerView. What am I missing?

It appears that the disk persistance that is enabled by default for Android was responsible for this behavior. Turning it off got me the result I wanted.