Presenter
abstract class Presenter : FacetProvider
kotlin.Any | |
↳ | androidx.leanback.widget.Presenter |
A Presenter is used to generate View
s 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 | |
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open |
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 |
Base class to perform a task on Presenter. |
Public constructors | |
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<init>() A Presenter is used to generate |
Public methods | |
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Any! | |
abstract Unit |
onBindViewHolder(viewHolder: Presenter.ViewHolder!, item: Any!) Binds a |
open Unit |
onBindViewHolder(viewHolder: Presenter.ViewHolder!, item: Any!, payloads: MutableList<Any!>!) Binds a |
abstract Presenter.ViewHolder! |
onCreateViewHolder(parent: ViewGroup!) Creates a new |
abstract Unit |
onUnbindViewHolder(viewHolder: Presenter.ViewHolder!) Unbinds a |
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 |