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 and/or data from a database while I'm just using a ListView (no special Activity) and an ArrayList of data. Does anyone know how I can implement that alphabetical-scroll feature in the Contacts list for my own ListView?

Edited Again

I followed this tutorial, which I thought would finally make it work, but I'm still getting a forced close.

class AlphabeticalAdapter extends ArrayAdapter<String> implements SectionIndexer
{
    private HashMap<String, Integer> alphaIndexer;
    private String[] sections;

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

        Set<String> sectionLetters = alphaIndexer.keySet();
        ArrayList<String> sectionList = new ArrayList<String>(sectionLetters);
        Collections.sort(sectionList);
        sections = new String[sectionList.size()];
        sectionList.toArray(sections);

    }

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

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

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

In the LogCat, it says java.lang.RuntimeException: Unable to resume activity {(package of another app I made) android.app.SuperNotCalledExcpetion. I thought that was really weird because I don't reference that other app at all in the one I'm working with. I tried uninstalling that other app, still got the forced close, but I could see what the LogCat said because it didn't update.

Final Edit

Here is the working code. Sorry for posting it something like 9 months overdue.

class AlphabeticalAdapter extends ArrayAdapter<String> implements SectionIndexer
{
    private HashMap<String, Integer> alphaIndexer;
    private String[] sections;

    public AlphabeticalAdapter(Context c, int resource, List<String> data)
    {
        super(c, resource, data);
        alphaIndexer = new HashMap<String, Integer>();
        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<String> sectionLetters = alphaIndexer.keySet();
        ArrayList<String> sectionList = new ArrayList<String>(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)
    {
        for ( int i = sections.length - 1; i >= 0; i-- ) {
            if ( position >= alphaIndexer.get( sections[ i ] ) ) {
                return i;
            }
        }
        return 0;
    }

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

Edit : getSectionForPosition is important if you want your scroller appear in the right place while you are scrolling. Returning only 1 (or 0) tells that you are just scrolling in the first (or second) section which will result in scroller's wrong position (mostly goes out of screen). Added code returns the appropriate section so scroller can know where it actually is.

Is there a reason you don't want to use ListActivity? Can you link to the tutorials you speak of? — i_am_jorf, Aug 20 '11 at 02:24
change getSectionForPosition to return 0; I get smoother scrolling at the bottom of the listview with that — MobileMon, Jan 29 '13 at 14:33
can you please post the whole code i implement it but it is not working for me i will be really thankful — Muhammad Younas, Jan 17 '17 at 06:08

score 21 · Accepted Answer · edited May 07 '13 at 07:47

21

I forgot to instantiate alphaIndexer. Works perfectly now.

class AlphabeticalAdapter extends ArrayAdapter<String> implements SectionIndexer
{
    private HashMap<String, Integer> alphaIndexer;
    private String[] sections;

    public AlphabeticalAdapter(Context c, int resource, List<String> data)
    {
        super(c, resource, data);
        alphaIndexer = new HashMap<String, Integer>();
        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<String> sectionLetters = alphaIndexer.keySet();
        ArrayList<String> sectionList = new ArrayList<String>(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;
    }
}

edited May 07 '13 at 07:47

Muhannad A.Alhariri

3,702
4
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46

answered Aug 20 '11 at 13:20

Pat Needham

5,698
7
43
63

@Pat: Hello i also want the final working demo if you have completed it. Thanks. – Shreyash Mahajan Jun 04 '12 at 07:01
@akdurmus sorry for the long delay. – Pat Needham Jun 08 '12 at 02:53
1

@Pat Nice one, really hard to find a proper tutorial on this subject but this worked out of the box. Thanks – Warpzit Aug 22 '13 at 11:18
guys i have used the above adapter, but its not showing any alphabets to the right ... is anything that i am missing – Goofy Dec 30 '13 at 16:49
What version of Android does your phone/emulator use, and which version are you targeting? That might make I difference – Pat Needham Dec 30 '13 at 16:57
@PatNeedham the alphabets are not showing up for me...do we need to add anything to my listview xml file...or the above is sufficient for the alphabets to show up?? – Zxxxxx Nov 18 '16 at 04:50
One improvement would be to use a collator: Collator coll = Collator.getInstance(); coll.setStrength(Collator.TERTIARY); Collections.sort(sectionList, coll); – Ahmet Noyan Kızıltan Feb 22 '18 at 14:32

Sashi Kolli · Answer 2 · 2011-08-20T02:37:18.557

3

If I understand you correctly, you want to set fastScrollEnabled=true and that will give you the little thumb scroller on the right. If you want to add a floating letter like the one in contacts, there is a great example in the APIDemos project in List9.java (http://www.devdaily.com/java/jwarehouse/android-examples/platforms/android-2/samples/ApiDemos/src/com/example/android/apis/view/List9.java.shtml)

edited Aug 20 '11 at 02:37

answered Aug 20 '11 at 02:24

Sashi Kolli

751
5
6

I think they are asking for actually seeing A, B, C, etc, similar to the iPhone contacts list UI. A custom scrollbar widget type thing. – i_am_jorf Aug 20 '11 at 02:27
There's a section and a visible dialog during scroll. And fastScrollEnabled is set to true on ListView. – Harald Wilhelm Aug 20 '11 at 06:15

How to show alphabetical letters on side of Android ListView

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