public abstract class Presenter extends Object implements FacetProvider
View
s 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 View.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 HorizontalGridView
and
VerticalGridView
to customize child alignment.Modifier and Type | Class and Description |
---|---|
static class |
Presenter.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.
|
static class |
Presenter.ViewHolderTask
Base class to perform a task on Presenter.ViewHolder.
|
Constructor and Description |
---|
Presenter() |
Modifier and Type | Method and Description |
---|---|
protected static void |
cancelAnimationsRecursive(View view)
Utility method for removing all running animations on a view.
|
Object |
getFacet(Class<?> facetClass)
Queries optional implemented facet.
|
abstract void |
onBindViewHolder(Presenter.ViewHolder viewHolder,
Object item)
Binds a
View to an item. |
abstract Presenter.ViewHolder |
onCreateViewHolder(ViewGroup parent)
Creates a new
View . |
abstract void |
onUnbindViewHolder(Presenter.ViewHolder viewHolder)
Unbinds a
View from an item. |
void |
onViewAttachedToWindow(Presenter.ViewHolder holder)
Called when a view created by this presenter has been attached to a window.
|
void |
onViewDetachedFromWindow(Presenter.ViewHolder holder)
Called when a view created by this presenter has been detached from its window.
|
void |
setFacet(Class<?> facetClass,
Object facetImpl)
Sets dynamic implemented facet in addition to basic Presenter functions.
|
void |
setOnClickListener(Presenter.ViewHolder holder,
View.OnClickListener listener)
Called to set a click listener for the given view holder.
|
public abstract Presenter.ViewHolder onCreateViewHolder(ViewGroup parent)
View
.public abstract void onBindViewHolder(Presenter.ViewHolder viewHolder, Object item)
View
to an item.public abstract void onUnbindViewHolder(Presenter.ViewHolder viewHolder)
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.public void onViewAttachedToWindow(Presenter.ViewHolder holder)
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.
holder
- Holder of the view being attachedpublic void onViewDetachedFromWindow(Presenter.ViewHolder holder)
Becoming detached from the window is not necessarily a permanent condition; the consumer of an presenter's views may choose to cache views offscreen while they are not visible, attaching and detaching them as appropriate.
Any view property animations should be cancelled here or the view may fail to be recycled.holder
- Holder of the view being detachedprotected static void cancelAnimationsRecursive(View view)
public void setOnClickListener(Presenter.ViewHolder holder, View.OnClickListener listener)
holder
- The view holder containing the view(s) on which the listener should be set.listener
- The click listener to be set.public final Object getFacet(Class<?> facetClass)
FacetProvider
getFacet
in interface FacetProvider
facetClass
- Facet classes to query, examples are: class of
ItemAlignmentFacet
.public final void setFacet(Class<?> facetClass, Object facetImpl)
facetClass
- Facet classes to query, can be class of ItemAlignmentFacet
.facetImpl
- Facet implementation.