Android Laggy AlphabetIndexer in ListView

I have a CustomCursorAdapter to do the nice section headers. I removed all images from the ListView rows but the scrolling is still rather laggy. Anyone knows a way to optimize this? The scrolling on applications like Viber for Contacts is really smooth even for 2000 contacts. Thanks!

public View getView(int position, View convertView, ViewGroup parent) {
    final int type = getItemViewType(position);
    if (type == TYPE_HEADER) {开发者_如何学Go
        if (convertView == null) {
            final LayoutInflater inflater = LayoutInflater.from(context);
            convertView = inflater.inflate(R.layout.list_header, parent,
                    false);
        }
        ((TextView) convertView.findViewById(R.id.list_header_title))
                .setText((String) getSections()[getSectionForPosition(position)]);
        return convertView;
    } else {
        View v = super.getView(
                position
                        - sectionToOffset
                                .get(getSectionForPosition(position)) - 1,
                convertView, parent);

        int contactIdCol = c.getColumnIndex(ContactsContract.CommonDataKinds.Phone.CONTACT_ID);

        String contactId_text = c.getString(contactIdCol);

        boolean flag = db.isRegistered(contactId_text);

        ImageView iv = (ImageView) v.findViewById(R.id.typeImage);
        if (flag) {
            iv.setImageResource(R.drawable.rocket);
        } else {

            iv.setMinimumHeight(Config.getIconSize(context));
            iv.setMinimumWidth(Config.getIconSize(context));
            iv.setImageDrawable(null);
        }

        ImageView iv1 = (ImageView) v.findViewById(R.id.test);

        cl.displayImage(contactId_text, iv1);

        return v;
    }

}

To further clarify, it's the fast scrolling that is jerky, the normal scroll seems fine.

You are creating a list view item every time "getView" is called. A good way to gain performance is to create a static "viewHolder" class wich represents the data of a view item.

e.g.

static class ViewHolder
{
    ImageView icon;
    TextView title;
}

in the "getView" method you can create an instance of the viewHolder then:

    if (convertView == null) {

        final LayoutInflater inflater = LayoutInflater.from(context);

        convertView = inflater.inflate(R.layout.list_header, parent, false);

        holder = new ViewHolder();
        holder.icon = (ImageView) convertView.findViewById(R.id.icon);
        holder.name = (TextView) convertView.findViewById(R.id.title);
        convertView.setTag(holder);

    }

and then fill the data of your holder:

if (item != null) {
    holder.title.setText("ItemTitle");
    holder.icon.setImageResource(R.drawable.rocket);
}

return convertView;

for a detailled example see also:

http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/view/List14.html