java - Firebase/Android: Adding retrieved values from Firebase to arraylist returns null pointer exception

Question

I'm trying the add the retrieved values from Firebase database to an Arraylist and from there to a String array. My retrieval method works fine. I can have all the values printed out in a toast. But apparently it doesn't get added to the arraylist.

Here's my code for retrieval in onActivityCreated() of fragment class.

ArrayList<String> allBrands = new ArrayList<>();
brandRef=FirebaseDatabase.getInstance().getReferenceFromUrl("https://stockmanager-142503.firebaseio.com/Brands");
        q=brandRef.orderByChild("brandName");
        q.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
               allBrands.add((dataSnapshot.getValue(Brand.class)).getBrandName());
                Toast.makeText(getActivity(),(dataSnapshot.getValue(Brand.class)).getBrandName(), Toast.LENGTH_SHORT).show();

            }

            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

And this is where I'm trying to use the arrayList in OnActivityResult() method of the Fragment class but the iterator loop is not executed I believe. The toast is not seen. I'm getting a null pointer exception when I try to work with the array. I assume the values do not get copied to the brands array.

count=allBrands.size();
                                String[] brands=new String[count];
                                Iterator<String> itemIterator = allBrands.iterator();
                                if(itemIterator.hasNext()){
                                    //brands[i] = itemIterator.next();
                                    Toast.makeText(getActivity(), itemIterator.next(), Toast.LENGTH_SHORT).show();
                                   // i++;

                                }
                               for( i=0;i<count;i++){
                                    if(brands[i].compareTo(Brand)==0){
                                        f=1;break;
                                    }
                                }

Here's my database in case that helps. But I can print out all the retrieved values in a Toast with no problem.

Answer 1

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