Android ListView with multiple select and custom adapter

Question

Hello, I have a ListView with a custom adapter. The ListView allows multiple select, but somehow it's not recognising when an item is selected.

I've already made the adapter items extend Checkable, but still the getCheckedItemPositions() returns an array of falses.

I guess there's something fundamental I'm doing wrong, but I have been unable so far to find examples of multiple select ListViews where the adapter was not an ArrayAdapter using the default layout for multiple selects.

Any help would be much appreciated.

Code is below:

Main class:

listView = (ListView) findViewById(R.id.cardlist);

tca = new TextCardAdapter(mInflater);
listView.setAdapter(tca);

Adapter:

public class TextCardAdapter extends BaseAdapter {
private int count = 0;
private List<CheckableCard> cardList = new ArrayList<CheckableCard>();
private LayoutInflater mInflater;

public TextCardAdapter(LayoutInflater inflater) {
    this.mInflater = inflater;
}

@Override
public int getCount() {
    return count;
}

@Override
public Object getItem(int position) {
    return cardList.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    final ViewHolder holder;
    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.textlayout_row, null, false);
        convertView.setClickable(true);

        holder = new ViewHolder();
        holder.text = (TextView) convertView.findViewById(R.id.card_name);
        holder.checkbox = (CheckBox) convertView.findViewById(R.id.checkbox);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    final CheckableCard card = cardList.get(position);

    holder.text.setText(card.card.toString());
    holder.checkbox.setChecked(card.isChecked());
    holder.checkbox.setOnClickListener(card.checkListener);
    convertView.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            card.checkListener.onClick(v);
            holder.checkbox.setChecked(card.isChecked());
        }
    });

    return convertView;
}

public void add(Card card) {
    cardList.add(new CheckableCard(card));
    count++;
    notifyDataSetChanged();
}

public void addAll(Collection<Card> cardColl) {
    for (Card c : cardColl)
        add(c);
}

public void removeAll() {
    count = 0;
    cardList.clear();
    notifyDataSetChanged();
}

public Card getCard(int position) {
    CheckableCard cc = (CheckableCard) getItem(position);
    if (cc == null) return null;
    return cc.card;
}

public class CheckableCard implements Checkable {
    private boolean checked = false;
    public final Card card;
    public final OnClickListener checkListener;

    public CheckableCard(Card card) {
        this.card = card;
        checkListener = new OnClickListener() {

            @Override
            public void onClick(View v) {
                toggle();
            }
        };
    }

    @Override
    public boolean isChecked() {
        return checked;
    }

    @Override
    public void setChecked(boolean checked) {
        this.checked = checked;
    }

    @Override
    public void toggle() {
        checked = !checked;
    }

}

static class ViewHolder {
    TextView text;
    CheckBox checkbox;
}
}