FacetProvider
public
interface
FacetProvider
| androidx.leanback.widget.FacetProvider |
This is the query interface to supply optional features(aka facets) on an object without the need
of letting the object to subclass or implement java interfaces. Facets allow leanback to
re-compose optional features from leanback ViewHolder to RecyclerView ViewHolder. A typical
"facet" class is ItemAlignmentFacet that defines how to align a ViewHolder inside
VerticalGridView or HorizontalGridView.
A FacetProvider could be retrieved from two sources by VerticalGridView/HorizontalGridView in
the following order.
ViewHolder based facet:
RecyclerView.ViewHolder can implement FacetProvider. If app uses leanback Presenter.ViewHolder, the facet of Presenter.ViewHolder will be relayed by ItemBridgeAdapter.ViewHolder which is a wrapper of Presenter.ViewHolder. ViewHolder based facet is used less frequently than item view type based facet because in most cases ViewHolders of same type share the same alignment definition.
For example, app calls viewHolder.setFacet(ItemAlignmentFacet.class, itemAlignmentFacet) to set alignment of the ViewHolder instance.
RecyclerView item view type based facet:
RecyclerView.Adapter can implement FacetProviderAdapter which returns FacetProvider
for each item view type. If app uses leanback ObjectAdapter and Presenter, app wraps
the ObjectAdapter and Presenter using ItemBridgeAdapter. The implementation of
ItemBridgeAdapter.getFacetProvider(int) will return the FacetProvider implemented
by Presenter which is mapped to the item view type.
For example, app calls presenter.setFacet(ItemAlignmentFacet.class, itemAlignmentFacet) to set alignment of all ViewHolders created by this Presenter.
Summary
Public methods | |
|---|---|
abstract
Object
|
getFacet(Class<?> facetClass)
Queries optional implemented facet. |
Public methods
getFacet
public abstract Object getFacet (Class<?> facetClass)
Queries optional implemented facet.
| Parameters | |
|---|---|
facetClass |
Class: Facet classes to query, examples are: class of
ItemAlignmentFacet. |
| Returns | |
|---|---|
Object |
Facet implementation for the facetClass or null if feature not implemented. |