ListView adapter

ListView listView;
ArrayList<String> list;
ArrayAdapter<String> adapter;
DatabaseReference data = FirebaseDatabase.getInstance().getReference();

listView = (ListView)findViewById(R.id.listView);
list = new ArrayList<String>();
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line, list);
listView.setAdapter(adapter);

data.onChildListener(){
    list.add(dataSnapshot.getKey(), dataSnapshot.getValue(String.class));
    adapter.notifyAdapterBrdene();
}