listSubject.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {

            String selectedSubject = listSubject.getItemAtPosition(i).toString();

            Intent intent = new Intent(getContext(), Topics.class);
            intent.putExtra("subjectname", selectedSubject);
            startActivity(intent);

        }
    });