I created a recyclerview that retrieves items from firebasefirestore when I delete a data from firebasefirestore recyclerview refresh itself normally but when I add an item to firebasefirestore it is refreshed but dublicates the datas and so many items appears in the recyclerview but it shouldnt, and when I enter other activity then exit to this activity a few times my recyclerview backs to normal.This is my method to fill the recyclerview:

private void fillArray() {
    NoteArray = new ArrayList<>();

    //SnapshotListener read and write data in real time 
    collectionReference.addSnapshotListener(new EventListener<QuerySnapshot>() {
       
        @Override
        public void onEvent(@Nullable QuerySnapshot value, @Nullable FirebaseFirestoreException error) {
            if(error !=null){
                Toast.makeText(recyclerview_notes.this,"Error " error.toString(),Toast.LENGTH_SHORT).show();
            }


            if (value!=null && !value.isEmpty()){
               
                  for(QueryDocumentSnapshot docs:value) {
                      Note note = docs.toObject(Note.class);
                              NoteArray.add(note);
                            
                }
                recyclerViewAdapter = new NotesRecyclerViewAdapter(NoteArray,recyclerViewInterface);
                recyclerView.setAdapter(recyclerViewAdapter);
                recyclerViewAdapter.notifyDataSetChanged();
          
            }

        }
    });

1.first I have 2 items in recyclerview:

2.then I added third item

3.it saves item but dublicates all items

4.when I enter other activity and exit a few times it is fixed

I want that when I add a data to firebase , my recyclerview updates normally.

CodePudding user response：

I think it shows the same data so many times but stored properly on database. Then just clear your list before adding data to the list. Like this NoteArray.clear();

See the updated code below

private void fillArray() {
    NoteArray = new ArrayList<>();

    //SnapshotListener read and write data in real time 
    collectionReference.addSnapshotListener(new EventListener<QuerySnapshot>() {
       
        @Override
        public void onEvent(@Nullable QuerySnapshot value, @Nullable FirebaseFirestoreException error) {
            if(error !=null){
                Toast.makeText(recyclerview_notes.this,"Error " error.toString(),Toast.LENGTH_SHORT).show();
            }


            if (value!=null && !value.isEmpty()){
                  NoteArray.clear(); // adding list clear function. If data is fetched successfully then the list gets cleared old data and fills new data.
                  for(QueryDocumentSnapshot docs:value) {
                      Note note = docs.toObject(Note.class);
                              NoteArray.add(note);
                            
                }
                recyclerViewAdapter = new NotesRecyclerViewAdapter(NoteArray,recyclerViewInterface);
                recyclerView.setAdapter(recyclerViewAdapter);
                recyclerViewAdapter.notifyDataSetChanged();
          
            }

        }
    });

Hope it helps