added in version 22.1.0
belongs to Maven artifact com.android.support:leanback-v17:28.0.0-alpha1

Presenter

public abstract class Presenter
extends Object implements FacetProvider

java.lang.Object
   ↳ android.support.v17.leanback.widget.Presenter
Known Direct Subclasses
Known Indirect Subclasses


A Presenter is used to generate Views and bind Objects to them on demand. It is closely related to the concept of an RecyclerView.Adapter, but is not position-based. The leanback framework implements the adapter concept using ObjectAdapter which refers to a Presenter (or PresenterSelector) instance.

Presenters should be stateless. Presenters typically extend Presenter.ViewHolder to store all necessary view state information, such as references to child views to be used when binding to avoid expensive calls to findViewById(int).

A trivial Presenter that takes a string and renders it into a TextView:

 public class StringTextViewPresenter extends Presenter {
     // This class does not need a custom ViewHolder, since it does not use
     // a complex layout.

     @Override
     public ViewHolder onCreateViewHolder(ViewGroup parent) {
         return new ViewHolder(new TextView(parent.getContext()));
     }

     @Override
     public void onBindViewHolder(ViewHolder viewHolder, Object item) {
         String str = (String) item;
         TextView textView = (TextView) viewHolder.mView;

         textView.setText(item);
     }

     @Override
     public void onUnbindViewHolder(ViewHolder viewHolder) {
         // Nothing to unbind for TextView, but if this viewHolder had
         // allocated bitmaps, they can be released here.
     }
 }
 
In addition to view creation and binding, Presenter allows dynamic interface (facet) to be added: setFacet(Class, Object). Supported facets:
  • ItemAlignmentFacet is used by