convertView in custom adapter with multiple line views

Question

I'm implementing custom adapter which handles multiple type of lines in a listview based on this (very useful) tutorial: http://logc.at/2011/10/10/handling-listviews-with-multiple-row-types/

Now, I thought I understood everything but one thing puzzles me. In the getView method we receive the convertView which suppose to be the view (group) with specific layout to display in the specific line in the listview.

public View getView(int position, View convertView, ViewGroup parent) {
    //first get the animal from our data model
    Animal animal = animals.get(position);

    //if we have an image so we setup an the view for an image row
    if (animal.getImageId() != null) {
        ImageRowViewHolder holder;
        View view;

        //don't have a convert view so we're going to have to create a new one
        if (convertView == null) {
            ViewGroup viewGroup = (ViewGroup)LayoutInflater.from(AnimalHome.this)
                    .inflate(R.layout.image_row, null);

            //using the ViewHolder pattern to reduce lookups
            holder = new ImageRowViewHolder((ImageView)viewGroup.findViewById(R.id.image),
                        (TextView)viewGroup.findViewById(R.id.title));
            viewGroup.setTag(holder);

            view = viewGroup;
        }
        //we have a convertView so we're just going to use it's content
        else {
            //get the holder so we can set the image
            holder = (ImageRowViewHolder)convertView.getTag();

            view = convertView;
        }

        //actually set the contents based on our animal
        holder.imageView.setImageResource(animal.getImageId());
        holder.titleView.setText(animal.getName());

        return view;
    }
    //basically the same as above but for a layout with title and description
    else {
        DescriptionRowViewHolder holder;
        View view;
        if (convertView == null) {
            ViewGroup viewGroup = (ViewGroup)LayoutInflater.from(AnimalHome.this)
                    .inflate(R.layout.text_row, null);
            holder = new DescriptionRowViewHolder((TextView)viewGroup.findViewById(R.id.title),
                    (TextView)viewGroup.findViewById(R.id.description));
            viewGroup.setTag(holder);
            view = viewGroup;
        } else {
            view = convertView;
            holder = (DescriptionRowViewHolder)convertView.getTag();
        }

        holder.descriptionView.setText(animal.getDescription());
        holder.titleView.setText(animal.getName());

        return view;
    }
}

However, in the case of multiple types of lines in the listview (for example, list of animals with separators lines with titles like 'mamals','fish','birds') how does the listview know what convertView to send? it can be one of two completely different types. something is very unclear to me. can someone explain please?

Answer 1

From the tutorial you provided :)

The two additional methods android Adapters provide for managing different row types are:

getItemViewType(int position) and getViewTypeCount(). The list view uses these methods create different pools of views to reuse for different types of rows.

Good Luck :)