Question

I am trying to display a sub-total of the database value bound to each row of my ListView. I don’t want to keep the sub-total as a database column, so I am trying to accumulate the values as they are displayed. Of course this brings up the obvious problems of how to deal with scrolling, which will display and re-display a value, messing up the running sub-total.

To elaborate, each listview row has two fields, a value and a sub-total. The value comes from a database row, the sub-total is the total of all database rows up to and including that row. I don’t want to include the sub-total into the database row if I don’t have to, because that would make inserting and deleting rows more difficult.

Any ideas?

Answer 1

Create a custom adapter, create an array to hold the subtotal and use that in your getView to maintain your subtotal even when scrolled.

public class CustomCursorAdapter extends SimpleCursorAdapter {

private Cursor c;
private Context context;
private Activity activity;
private int[] subtotal;
private int subtotalhold;
private int layout;

public CustomCursorAdapter(Context context, int layout, Cursor c,
        String[] from, int[] to) {
    super(context, layout, c, from, to);

    this.c = c;
    this.context = context;
    this.activity = (Activity) context;
    this.layout = layout;

    subtotal = new int[c.getCount()];
    subtotalhold=0;
    c.moveToFirst();
    int i = 0;
    while (c.isAfterLast() == false) {
        subtotalhold = subtotalhold + c.getInt(columnIndex);
        subtotal[i] = subtotalhold;
        i++;
        c.moveToNext();
    }
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null)
        convertView = View.inflate(context, layout, null);
    c.moveToPosition(position);

    TextView subtotal = (TextView) convertView.findViewById(R.id.subtotal);
            subtotal.setText(subtotal[position]);

            // rest of your code to populate the list row
    return (row);
    }
}