public class AppointmentsFragment extends Fragment {

    ArrayAdapter<Appointment> mAppointmentsArrayAdapter;

    List<Appointment> mAppointmentList = new ArrayList<>();
....
....
    private class GetAppointmentsAsyncTask extends AsyncTask<Void, Void, List<Appointment>> {

        @Override
        protected List<Appointment> doInBackground(Void... params) {
            APIService api = ApiAdapter.getInstance();
            List<Appointment> appointments = new ArrayList<Appointment>();
            try {
                List<Booking>  bookingList  = api.getBookings();

                for (Booking booking : bookingList) {
                    appointments.add(new Appointment(booking));
                }
            } catch (RetrofitError r) {
                Log.d(TAG, r.getMessage());
            }
            return appointments;
        }

        protected void onPostExecute(List<Appointment> appointments) {
            mAppointmentsArrayAdapter.clear();
            mAppointmentsArrayAdapter.addAll(appointments);

            for(int i=0 ; i<mAppointmentsArrayAdapter.getCount() ; i++){
                Appointment obj = mAppointmentsArrayAdapter.getItem(i);
                Log.d(TAG, obj.toString());
            }

            mAppointmentListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    Toast.makeText(getActivity().getApplicationContext(), "Clicked.",
                            Toast.LENGTH_SHORT).show();
                }
            });
            mAppointmentsArrayAdapter.notifyDataSetChanged();
        }
    }

}