Arraylist .add is not working inside loop

Question

I am having some sort of problem with the homeContent Arraylist. Have a look at the code...

        ArrayList<String> homeContent=new ArrayList<>(); //its actually a global list but I'm showing inside just show I've declared and initialised it.
        contentDb=FirebaseDatabase.getInstance().getReference().child("home");
        contentDb.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for(DataSnapshot ds: dataSnapshot.getChildren()){
                    tag=ds.getValue(String.class);
                    homeContent.add(tag);
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                Toast.makeText(getActivity(), "Error Connecting to the Server", Toast.LENGTH_SHORT).show();
            }
        });
        for(int i=0;i<homeContent.size();i++){
            Log.i("Entry",homeContent.get(i));
        }

So I used Log.i to track where the problem is and so I found out that the elements are being added in the list but as soon as it comes out of the loop and the valueEventListener function, it's back to having 0 elements in it.

EDIT: Turns out nothing inside that loop is staying permanently

Answer 1

Ok so thanks to Johannes Kuhn, the problem has been solved, actually the for loop was being executed after the event handler was being called so I had to put the loop inside the event handler.

Answer 2

ArrayList<String>   arrayList = null;  
contentDb=FirebaseDatabase.getInstance().getReference().child("home");
    contentDb.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for(DataSnapshot ds: dataSnapshot.getChildren()){
                tag=ds.getValue(String.class);
                arrayList = new ArrayList<>();
                arrayList.add(tag); // Add into list like this
            }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            Toast.makeText(getActivity(), "Error Connecting to the Server", Toast.LENGTH_SHORT).show();
        }
    });

Better you can add that value into list like I have shared above.