Presenter

Kotlin |Java

abstract class Presenter : FacetProvider

kotlin.Any
↳	androidx.leanback.widget.Presenter

Known Direct Subclasses

AbstractDetailsDescriptionPresenter, DetailsOverviewLogoPresenter, DividerPresenter, RowHeaderPresenter, RowPresenter, VerticalGridPresenter

AbstractDetailsDescriptionPresenter	An abstract `Presenter` for rendering a detailed description of an item.
DetailsOverviewLogoPresenter	Presenter that responsible to create a ImageView and bind to DetailsOverviewRow.
DividerPresenter	DividerPresenter provides a default presentation for `DividerRow` in HeadersFragment.
RowHeaderPresenter	RowHeaderPresenter provides a default presentation for `HeaderItem` using a `RowHeaderView` and optionally a TextView for description.
RowPresenter	An abstract `Presenter` that renders an Object in RowsFragment, the object can be subclass `Row` or a generic one.
VerticalGridPresenter	A presenter that renders objects in a `VerticalGridView`.

Known Indirect Subclasses

AbstractMediaItemPresenter, AbstractMediaListHeaderPresenter, DetailsOverviewRowPresenter, FullWidthDetailsOverviewRowPresenter, ListRowPresenter, PlaybackControlsRowPresenter, PlaybackRowPresenter, PlaybackTransportRowPresenter

AbstractMediaItemPresenter	Abstract `Presenter` class for rendering media items in a playlist format.
AbstractMediaListHeaderPresenter	Abstract presenter class for rendering the header for a list of media items in a playlist.
DetailsOverviewRowPresenter	Renders a `DetailsOverviewRow` to display an overview of an item.
FullWidthDetailsOverviewRowPresenter	Renders a `DetailsOverviewRow` to display an overview of an item.
ListRowPresenter	ListRowPresenter renders `ListRow` using a `HorizontalGridView` hosted in a `ListRowView`.
PlaybackControlsRowPresenter	A PlaybackControlsRowPresenter renders a `PlaybackControlsRow` to display a series of playback control buttons.
PlaybackRowPresenter	Subclass of `RowPresenter` that can define the desired behavior when the view reappears.
PlaybackTransportRowPresenter	A PlaybackTransportRowPresenter renders a `PlaybackControlsRow` to display a series of playback control buttons.

A Presenter is used to generate Views and bind Objects to them on demand. It is closely related to the concept of an , 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 ViewHolder to store all necessary view state information, such as references to child views to be used when binding to avoid expensive calls to View#findViewById(int).

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

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 HorizontalGridView and VerticalGridView to customize child alignment.

Summary

Nested classes
open	`ViewHolder` ViewHolder can be subclassed and used to cache any view accessors needed to improve binding performance (for example, results of findViewById) without needing to subclass a View.
abstract	`ViewHolderTask` Base class to perform a task on Presenter.

Public constructors
`<init>()` A Presenter is used to generate `View`s and bind Objects to them on demand.

Public methods
Any!	`getFacet(facetClass: Class<*>!)`
abstract Unit	`onBindViewHolder(viewHolder: Presenter.ViewHolder!, item: Any!)` Binds a `View` to an item.
open Unit	`onBindViewHolder(viewHolder: Presenter.ViewHolder!, item: Any!, payloads: MutableList<Any!>!)` Binds a `View` to an item with a list of payloads.
abstract Presenter.ViewHolder!	`onCreateViewHolder(parent: ViewGroup!)` Creates a new `View`.
abstract Unit	`onUnbindViewHolder(viewHolder: Presenter.ViewHolder!)` Unbinds a `View` from an item.
open Unit	`onViewAttachedToWindow(holder: Presenter.ViewHolder!)` Called when a view created by this presenter has been attached to a window.
open Unit	`onViewDetachedFromWindow(holder: Presenter.ViewHolder!)` Called when a view created by this presenter has been detached from its window.
Unit	`setFacet(facetClass: Class<*>!, facetImpl: Any!)` Sets dynamic implemented facet in addition to basic Presenter functions.
open Unit	`setOnClickListener(holder: Presenter.ViewHolder!, listener: OnClickListener!)` Called to set a click listener for the given view holder.

Protected methods
open static Unit	`cancelAnimationsRecursive(view: View!)` Utility method for removing all running animations on a view.

Public constructors

<init>

Presenter()

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

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 HorizontalGridView and VerticalGridView to customize child alignment.

Public methods

getFacet

fun getFacet(facetClass: Class<*>!): Any!

onBindViewHolder

abstract fun onBindViewHolder(
    viewHolder: Presenter.ViewHolder!, 
    item: Any!
): Unit

Binds a View to an item.

onBindViewHolder

open fun onBindViewHolder(
    viewHolder: Presenter.ViewHolder!, 
    item: Any!, 
    payloads: MutableList<Any!>!
): Unit

Binds a View to an item with a list of payloads.

Parameters
`viewHolder`	Presenter.ViewHolder!: The ViewHolder which should be updated to represent the contents of the item at the given position in the data set.
`item`	Any!: The item which should be bound to view holder.
`payloads`	MutableList<Any!>!: A non-null list of merged payloads. Can be empty list if requires full update.

onCreateViewHolder

abstract fun onCreateViewHolder(parent: ViewGroup!): Presenter.ViewHolder!

Creates a new View.

onUnbindViewHolder

abstract fun onUnbindViewHolder(viewHolder: Presenter.ViewHolder!): Unit

Unbinds a View from an item. Any expensive references may be released here, and any fields that are not bound for every item should be cleared here.

onViewAttachedToWindow

open fun onViewAttachedToWindow(holder: Presenter.ViewHolder!): Unit

Called when a view created by this presenter has been attached to a window.

This can be used as a reasonable signal that the view is about to be seen by the user. If the adapter previously freed any resources in onViewDetachedFromWindow(ViewHolder) those resources should be restored here.

Parameters
`holder`	Presenter.ViewHolder!: Holder of the view being attached