How to show alphabetical letters on side of Android ListView

Question

I\'ve looked at a lot of tutorials for making a ListView have the alphabetical letters on the side (like the Contacts list), but they all seem to using a ListActivity class

Answer 1

I forgot to instantiate alphaIndexer. Works perfectly now.

class AlphabeticalAdapter extends ArrayAdapter implements SectionIndexer
{
    private HashMap alphaIndexer;
    private String[] sections;

    public AlphabeticalAdapter(Context c, int resource, List data)
    {
        super(c, resource, data);
        alphaIndexer = new HashMap();
        for (int i = 0; i < data.size(); i++)
        {
            String s = data.get(i).substring(0, 1).toUpperCase();
            if (!alphaIndexer.containsKey(s))
                alphaIndexer.put(s, i);
        }

        Set sectionLetters = alphaIndexer.keySet();
        ArrayList sectionList = new ArrayList(sectionLetters);
        Collections.sort(sectionList);
        sections = new String[sectionList.size()];
        for (int i = 0; i < sectionList.size(); i++)
            sections[i] = sectionList.get(i);   
    }

    public int getPositionForSection(int section)
    {   
        return alphaIndexer.get(sections[section]);
    }

    public int getSectionForPosition(int position)
    {
        return 1;
    }

    public Object[] getSections()
    {
        return sections;
    }
}