"Whack a checkbox" game with ListView

Question

I have a ListActivity that was originally using an ArrayAdapter. Each item in my ListView contains a checkbox.

I changed Adapters to a CursorAdapter. Everything is working fine except checkboxes are out of control. For example: When I click the checkbox in position 1, the checkbox in position 4 gets checked. If I click the checkbox in position 1 again, it will check (Ie: When I click the checkbox in position 1, if the checkbox in position 4 is not checked, the checkbox in position 4 will get checked; else, the checkbox in position 1 is checked). Unchecking checkboxes doesn't seem to show any weird behavior. Any ideas why?

Update: It's checking the checkbox backwards based on how many items are on screen. What I mean is, if there are 5 items visible, clicking the 1st one will check the 5th, clicking the 2nd one with check the 4th, clicking the 3rd one will check the 3rd one. Also, once one has been checked, they all start behaving properly.

Apparently commenting out this makes the problem go away:

    if (holder.chkSelect != null) {
        holder.chkSelect.setOnCheckedChangeListener(this);
    }

This definitely has something to do with showMultiPanel popping up and possibly reducing the number of rows that can be seen. Though I don't understand why it worked fine with an ArrayAdapter.

Here is a copy of my CursorAdapter

public class InboxAdapter extends CursorAdapter implements CheckBox.OnCheckedChangeListener {
    private int mCheckedCount = 0;

    public InboxAdapter(Context context, Cursor c) {
        super(context, c);
    }

    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        if (buttonView.getId() == R.id.inbox_itemcheck) {
            if (isChecked) {
                mCheckedCount++;
            }
            else {
                mCheckedCount--;
            }
            ActivityInbox.this.showMultiPanel((mCheckedCount > 0) ? true : false);
        }
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        InboxHolder holder = (InboxHolder)view.getTag();

        if (holder.txtDate != null) {
            DateFormat df = new SimpleDateFormat("MM/dd/yyyy");
            Date d = new Date(cursor.getInt(cursor.getColumnIndex("created_on")) * 1000L);
            holder.txtDate.setText(df.format(d));
        }
        if (holder.txtSubject != null) {
            holder.txtSubject.setText(cursor.getString(cursor.getColumnIndex("subject")));
            if (cursor.getInt(cursor.getColumnIndex("read")) == 0) {
                holder.txtSubject.setTypeface(null, Typeface.BOLD);
            }
            else {
                holder.txtSubject.setTypeface(null, Typeface.NORMAL);
            }
        }

        if(holder.txtSummary != null) {
            holder.txtSummary.setText(cursor.getString(cursor.getColumnIndex("summary")));
        }

        if (cursor.getInt(cursor.getColumnIndex("read")) == 0) {
            view.setBackgroundResource(R.drawable.selector_inbox_unread);
        }
        else {
            view.setBackgroundResource(R.drawable.selector_inbox_read);
        }

        if (holder.lMessageType != null) {
            if (cursor.getInt(cursor.getColumnIndex("read")) == 0) {
                holder.lMessageType.setVisibility(View.VISIBLE);
            }
            else {
                holder.lMessageType.setVisibility(View.INVISIBLE);
            }
        }
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View v = inflater.inflate(R.layout.layout_inbox_item, parent, false);

        InboxHolder holder = new InboxHolder();
        holder.txtDate = (TextView) v.findViewById(R.id.inbox_item_date);
        holder.txtSubject = (TextView) v.findViewById(R.id.inbox_item_subject);
        holder.txtSummary = (TextView) v.findViewById(R.id.inbox_item_summary);
        holder.chkSelect = (CheckBox) v.findViewById(R.id.inbox_itemcheck);
        holder.lMessageType = (LinearLayout) v.findViewById(R.id.inbox_messagetype);

        v.setTag(holder);

        if (holder.chkSelect != null) {
            holder.chkSelect.setOnCheckedChangeListener(this);
        }
        return v;
    }

}

Answer 1

Note that a ListView can reuse a single View for more than one row of the table, and it's up to the adapter to decide whether that happens. I believe CursorAdapter is set up to do this where possible by pooling view instances and only creating enough to build the screen.

For a simple solution for a short list, just stick with an ArrayAdapter, and read all the data ahead of time. This avoids the whole issue.

If you want to stick with CursorAdapter, you need to store the checked states yourself. One way would be keeping a HashSet of the id's that are checked. In your checkbox click listener, update it by either adding or removing that row's id in the set. In bindView, set the checkbox state based on the whether the row's id is in the map. You may also want to set the listener in bindView, where you can have a final local variable set to the id, and can use that value in the code for the listener.