Not able to get fast scrolling working on ExpandableListView

Question

I can't seem to get fast scrolling working with my ExpandableListView. What's more is that the SectionIndexer methods I have implemented in my adapter are never actually called and I have verified this via breakpoints.

Here is my activity:

private void onCreate(Bundle a) {
     ...
     setContentView(R.layout.mylayout);
     ...
     setListAdapter(myAdapter);
     getExpandableListView().setFastScrollEnabled(true);
}

Here's my layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

    <ExpandableListView android:id="@+id/android:list"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fastScrollEnabled="true"/>

    <TextView android:id="@+id/android:empty"
            android:text="EMPTY! DOOM!"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
</LinearLayout>

Here's my adapter, which works by the way:

public class Adapter extends AbstractExpandableListAdapter<TTD, TTL>
        implements SectionIndexer {

    public static class TTDHolder {
        TextView title;
    }

    public static class TTLHolder {
        TextView title;
        ImageView icon;
    }

    private final Pattern alphaMatch = Pattern.compile("^[a-zA-Z]$");

    private final Pattern numberMatch = Pattern.compile("^\\d$");

    private LayoutInflater inflater;

    public Adapter(Context context, int groupClosedView, int groupExpandedView, int childView,
            List<Entry<TTD, List<TTL>>> objects) {
        super(context, groupClosedView, groupExpandedView, childView, objects);
        this.inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    public View getGroupView(int groupPosition, boolean isExpanded,
            View convertView, ViewGroup parent) {
        TTDHolder holder;

        if (convertView != null) {
            holder = (TTDHolder)convertView.getTag();
        } else {
            convertView = inflater.inflate(R.layout.item, parent, false);

            holder = new TTDHolder();
            holder.title = (TextView) convertView.findViewById(R.id.item_title);

            convertView.setTag(holder);
        }

        holder.title.setText(this.getObjects().get(groupPosition).getKey().getName());

        return convertView;
    }

    public View getChildView(int groupPosition, int childPosition,
            boolean isLastChild, View convertView, ViewGroup parent) {
        TTLHolder holder;

        if (convertView != null) {
            holder = (TTLHolder) convertView.getTag();
        } else {
            convertView = inflater.inflate(R.layout.item, parent, false);

            holder = new TTLHolder();
            holder.title = (TextView) convertView.findViewById(R.id.item_title);
            holder.icon = (ImageView) convertView.findViewById(R.id.item_icon);

            convertView.setTag(holder);
        }

        holder.title.setText(this.getObjects().get(groupPosition).getValue()
                .get(childPosition).getName());

        return convertView;
    }

    public Object[] getSections() {
        return "*1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");
    }

    public int getPositionForSection(int section) {
        for (Entry<TTD, List<TTL>> entry : this.getObjects()) {
            if (entry.getKey().getName().substring(0, 1) == getSections()[section])
                return this.getObjects().indexOf(entry);
        }

        return 0;
    }

    public int getSectionForPosition(int position) {
        List<Object> sections = Arrays.asList(getSections());
        return sections.indexOf(this.getObjects().get(position).getKey().getName().substring(0, 1).toUpperCase());
    }
}

However, when I scroll, I never see the fast scroller show up, nor are the SectionIndexer methods ever actually called.

Answer 1

As it turns out, you need to have a minimum number of items in your adapter in order for the fast-view scroller to show up.