Android: Smooth scrolling tricks (ListView)

@Override
 public View getGroupView(int groupPosition, boolean isExpanded,
   View convertView, ViewGroup parent) {

  ViewHolder holder;

  if (convertView == null) {
   
   convertView = mInflater.inflate(R.layout.row, null);

   holder = createViewHolder(convertView);
   
   convertView.setTag(holder);

  } else {

   holder = (ViewHolder) convertView.getTag();
  }
  
  IModel model = getGroup(groupPosition);
  
  holder.text1.setText(model.getText1());
  holder.layout.setBackgroundColor(context.getBackgroundColor(model));
  
  return convertView;
 }


private ViewHolder createViewHolder(View convertView) {

  ViewHolder holder;
  holder = new ViewHolder();

  holder.text1 = (TextView) convertView.findViewById(R.id.row_text1);
  holder.layout = (LinearLayout) convertView.findViewById(R.id.layoutRow);

  return holder;
 }