我正在实施一个列表。里面有很多项目，当我从列表中选择一个项目时，为列表项目设置颜色。当我滚动列表视图时，它会消失。
可能是什么原因？适配器代码如下：
public class CustomListViewAdapterProduct extends
ArrayAdapter<HashMap<String, Object>>
{
Context context;
public CustomListViewAdapterProduct(Context context, int resourceId,
ArrayList<HashMap<String, Object>> Strings) {
super(context, resourceId, Strings);
this.context = context;
}
/* private view holder class */
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
LayoutInflater mInflater = (LayoutInflater) context
.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
if (convertView == null) {
convertView = mInflater.inflate(R.layout.list_item_detail, null);
holder = new ViewHolder();
holder.txtProduct = (TextView) convertView.findViewById(R.id.product);
holder.txtCode = (TextView) convertView.findViewById(R.id.code);
convertView.setTag(holder);
convertView.setBackgroundResource((position % 2) == 0 ? R.color.light
: R.color.dark);
} else {
if (position == selectedPosition) {
convertView.setBackgroundColor(getResources().getColor(
R.color.selectedvalues));
} else {
convertView
.setBackgroundResource((position % 2) == 0 ? R.color.light
: R.color.dark);
}
holder = (ViewHolder) convertView.getTag();
}
holder.txtProduct.setText((this.getItem(position)
.get("description").toString()));
holder.txtCode.setText((this.getItem(position).get("quantity")
.toString()));
return convertView;
}
}