ListView中RadioButton实现单项选择

public class FragmentHack5 extends Fragment {
    View view;
    ListView lvCountries;
    Button btnShow;
    CountryListAdapter adapter;
    List<String> list;

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        list = new ArrayList<String>();
        list.add("中国");
        list.add("俄罗斯");
        list.add("美国");
        list.add("德国");
        list.add("英国");
        list.add("西班牙");
        list.add("法国");
        list.add("巴西");
        list.add("印度");

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_hack5,container,false);

        btnShow = (Button)view.findViewById(R.id.btnShow);
        lvCountries = (ListView)view.findViewById(R.id.lvCountries);

        adapter = new CountryListAdapter(getActivity(),R.layout.list_country_item,list);

        lvCountries.setAdapter(adapter);

        btnShow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(getActivity(),adapter.getChoiceCountry(),Toast.LENGTH_SHORT).show();;
            }
        });

        return view;
    }
}

public class CountryListAdapter extends ArrayAdapter<String>{

    int resourceId;
    int choiceId = -1;

    public CountryListAdapter(Context context, int resourceId, List<String> objects){
        super(context,resourceId,objects);

        this.resourceId = resourceId;
    }



    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        String country = getItem(position);
        final ViewHolder holder;

        if(convertView==null){
            holder = new ViewHolder();
            convertView = LayoutInflater.from(getContext()).inflate(resourceId,null);

            holder.rbCountry = (RadioButton)convertView.findViewById(R.id.rbCountry);

            convertView.setTag(holder);
        }else{
            holder = (ViewHolder)convertView.getTag();
        }

        holder.rbCountry.setText(country);

        if(choiceId==position){
            holder.rbCountry.setChecked(true);
        }else{
            holder.rbCountry.setChecked(false);
        }


        holder.rbCountry.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(holder.rbCountry.isChecked()){
                    choiceId = position;//记住当前选中的下标
                    CountryListAdapter.this.notifyDataSetChanged();
                }
            }
        });

        return convertView;
    }

    static class ViewHolder{
        public RadioButton rbCountry;
    }


    public String getChoiceCountry(){
        return getItem(choiceId);
    }
}