btn_a.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            PopupMenu a_popup = new PopupMenu(getActivity().getApplicationContext(), a_period);
            a_popup.getMenuInflater().inflate(R.menu.popup_a, a_popup.getMenu());

            a_popup.setOnMenuItemClickListener(new OnMenuItemClickListener() {

                @Override
                public boolean onMenuItemClick(MenuItem item) {
                    Toast.makeText(getActivity().getApplicationContext(), "Clicked "+item.getTitle(), Toast.LENGTH_SHORT).show();
                    return true;
                }
            });
            a_popup.show();
        }
    });