Question

public class CustomAdapter extends BaseAdapter

I found a code that extends BaseAdapter

        public View getView(int index, View view, final ViewGroup parent) {

            if (view == null) {
                LayoutInflater inflater = LayoutInflater.from(parent.getContext());
                view = inflater.inflate(R.layout.single_list_item, parent, false);
            }
    }

 TextView textView = (TextView) view.findViewById(R.id.tv_string_data);
        textView.setText(dataModel.getName());

my question is when view == null ?

why we need the code if (view == null) {}

thanks

Answer 1

A ListView typically contain more data then the number of displayed rows. If the user scrolls the list then rows and their associated Views will be scrolled out of the visible area. The Java objects which represents the rows can be reused for newly visible rows.

If Android determines that a View which represents a row is not visible anymore it allows the getView() method to reuse it via the convertView parameter.

A performance optimized adapter assigns the new data to the convertView. This avoids inflating an XML file and creating new Java objects.

In case no View is available for reuse, Android will pass null to the convertView parameter. Therefore the adapter implementation need to check for this.