RecyclerView.Adapter

public abstract class RecyclerView.Adapter<VH extends RecyclerView.ViewHolder>

Known direct subclasses
ConcatAdapter

An Adapter implementation that presents the contents of multiple adapters in sequence.
FragmentStateAdapter

Similar in behavior to FragmentStatePagerAdapter
ItemBridgeAdapter

Bridge from Presenter to RecyclerView.Adapter.
LeanbackListPreferenceDialogFragment.AdapterMulti

This class is deprecated.

Ue LeanbackListPreferenceDialogFragmentCompat.
LeanbackListPreferenceDialogFragment.AdapterSingle

This class is deprecated.

Use LeanbackListPreferenceDialogFragmentCompat.
ListAdapter

RecyclerView.Adapter base class for presenting List data in a RecyclerView, including computing diffs between Lists on a background thread.
LoadStateAdapter

Adapter for displaying a RecyclerView item based on LoadState, such as a loading spinner, or a retry error button.
PagedListAdapter

This class is deprecated. PagedListAdapter is deprecated and has been replaced by PagingDataAdapter
PagingDataAdapter

RecyclerView.Adapter base class for presenting paged data from PagingDatas in a RecyclerView.

Base class for an Adapter

Adapters provide a binding from an app-specific data set to views that are displayed within a RecyclerView.

Parameters
<VH extends RecyclerView.ViewHolder>

A class that extends ViewHolder that will be used by the adapter.

Summary

Nested types

Defines how this Adapter wants to restore its state after a view reconstruction (e.g. configuration change).

Public constructors

Public methods
final void
bindViewHolder(@NonNull VH holder, int position)

This method internally calls onBindViewHolder to update the ViewHolder contents with the item at the given position and also sets up some private fields to be used by RecyclerView.
final @NonNull VH
createViewHolder(@NonNull ViewGroup parent, int viewType)

This method calls onCreateViewHolder to create a new ViewHolder and initializes some private fields to be used by RecyclerView.
int
findRelativeAdapterPositionIn(
    @NonNull RecyclerView.Adapter<RecyclerView.ViewHolder> adapter,
    @NonNull RecyclerView.ViewHolder viewHolder,
    int localPosition
)

Returns the position of the given ViewHolder in the given Adapter.
abstract int

Returns the total number of items in the data set held by the adapter.
long
getItemId(int position)

Return the stable ID for the item at position.
int
getItemViewType(int position)

Return the view type of the item at position for the purposes of view recycling.
final @NonNull RecyclerView.Adapter.StateRestorationPolicy

Returns when this Adapter wants to restore the state.
final boolean

Returns true if one or more observers are attached to this adapter.
final boolean

Returns true if this adapter publishes a unique long value that can act as a key for the item at a given position in the data set.
final void

Notify any registered observers that the data set has changed.
final void
notifyItemChanged(int position)

Notify any registered observers that the item at position has changed.
final void
notifyItemChanged(int position, @Nullable Object payload)

Notify any registered observers that the item at position has changed with an optional payload object.
final void
notifyItemInserted(int position)

Notify any registered observers that the item reflected at position has been newly inserted.
final void
notifyItemMoved(int fromPosition, int toPosition)

Notify any registered observers that the item reflected at fromPosition has been moved to toPosition.
final void
notifyItemRangeChanged(int positionStart, int itemCount)

Notify any registered observers that the itemCount items starting at position positionStart have changed.
final void
notifyItemRangeChanged(
    int positionStart,
    int itemCount,
    @Nullable Object payload
)

Notify any registered observers that the itemCount items starting at position positionStart have changed.
final void
notifyItemRangeInserted(int positionStart, int itemCount)

Notify any registered observers that the currently reflected itemCount items starting at positionStart have been newly inserted.
final void
notifyItemRangeRemoved(int positionStart, int itemCount)

Notify any registered observers that the itemCount items previously located at positionStart have been removed from the data set.
final void
notifyItemRemoved(int position)

Notify any registered observers that the item previously located at position has been removed from the data set.
void

Called by RecyclerView when it starts observing this Adapter.
abstract void
onBindViewHolder(@NonNull VH holder, int position)

Called by RecyclerView to display the data at the specified position.
void
onBindViewHolder(
    @NonNull VH holder,
    int position,
    @NonNull List<Object> payloads
)

Called by RecyclerView to display the data at the specified position.
abstract @NonNull VH
onCreateViewHolder(@NonNull ViewGroup parent, int viewType)

Called when RecyclerView needs a new ViewHolder of the given type to represent an item.
void

Called by RecyclerView when it stops observing this Adapter.
boolean

Called by the RecyclerView if a ViewHolder created by this Adapter cannot be recycled due to its transient state.
void

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

Called when a view created by this adapter has been detached from its window.
void
onViewRecycled(@NonNull VH holder)

Called when a view created by this adapter has been recycled.
void

Register a new observer to listen for data changes.
void
setHasStableIds(boolean hasStableIds)

Indicates whether each item in the data set can be represented with a unique identifier of type java.lang.Long.
void

Sets the state restoration strategy for the Adapter.
void

Unregister an observer currently listening for data changes.

Public constructors

Adapter

Added in 1.0.0
public Adapter()

Public methods

bindViewHolder

Added in 1.0.0
public final void bindViewHolder(@NonNull VH holder, int position)

This method internally calls onBindViewHolder to update the ViewHolder contents with the item at the given position and also sets up some private fields to be used by RecyclerView. Adapters that merge other adapters should use bindViewHolder when calling nested adapters so that RecyclerView can track which adapter bound the ViewHolder to return the correct position from getBindingAdapterPosition method. They should also override the findRelativeAdapterPositionIn method.

Parameters
@NonNull VH holder

The view holder whose contents should be updated
int position

The position of the holder with respect to this adapter
See also
onBindViewHolder

createViewHolder

Added in 1.0.0
public final @NonNull VH createViewHolder(@NonNull ViewGroup parent, int viewType)

This method calls onCreateViewHolder to create a new ViewHolder and initializes some private fields to be used by RecyclerView.

See also
onCreateViewHolder

findRelativeAdapterPositionIn

Added in 1.2.0
public int findRelativeAdapterPositionIn(
    @NonNull RecyclerView.Adapter<RecyclerView.ViewHolder> adapter,
    @NonNull RecyclerView.ViewHolder viewHolder,
    int localPosition
)

Returns the position of the given ViewHolder in the given Adapter. If the given Adapter is not part of this Adapter, NO_POSITION is returned.

Parameters
@NonNull RecyclerView.Adapter<RecyclerView.ViewHolder> adapter

The adapter which is a sub adapter of this adapter or itself.
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder whose local position in the given adapter will be returned.
int localPosition

The position of the given ViewHolder in this Adapter.
Returns
int

The local position of the given ViewHolder in this Adapter or NO_POSITION if the ViewHolder is not bound to an item or the given Adapter is not part of this Adapter (if this Adapter merges other adapters).

getItemCount

Added in 1.0.0
public abstract int getItemCount()

Returns the total number of items in the data set held by the adapter.

Returns
int

The total number of items in this adapter.

getItemId

Added in 1.0.0
public long getItemId(int position)

Return the stable ID for the item at position. If hasStableIds would return false this method should return NO_ID. The default implementation of this method returns NO_ID.

Parameters
int position

Adapter position to query
Returns
long

the stable ID of the item at position

getItemViewType

Added in 1.0.0
public int getItemViewType(int position)

Return the view type of the item at position for the purposes of view recycling.

The default implementation of this method returns 0, making the assumption of a single view type for the adapter. Unlike ListView adapters, types need not be contiguous. Consider using id resources to uniquely identify item view types.

Parameters
int position

position to query
Returns
int

integer value identifying the type of the view needed to represent the item at position. Type codes need not be contiguous.

getStateRestorationPolicy

Added in 1.2.0
public final @NonNull RecyclerView.Adapter.StateRestorationPolicy getStateRestorationPolicy()

Returns when this Adapter wants to restore the state.

Returns
@NonNull RecyclerView.Adapter.StateRestorationPolicy

The current StateRestorationPolicy for this Adapter. Defaults to ALLOW.
See also
setStateRestorationPolicy

hasObservers

Added in 1.0.0
public final boolean hasObservers()

Returns true if one or more observers are attached to this adapter.

Returns
boolean

true if this adapter has observers

hasStableIds

Added in 1.0.0
public final boolean hasStableIds()

Returns true if this adapter publishes a unique long value that can act as a key for the item at a given position in the data set. If that item is relocated in the data set, the ID returned for that item should be the same.

Returns
boolean

true if this adapter's items have stable IDs

notifyDataSetChanged

Added in 1.0.0
public final void notifyDataSetChanged()

Notify any registered observers that the data set has changed.

There are two different classes of data change events, item changes and structural changes. Item changes are when a single item has its data updated but no positional changes have occurred. Structural changes are when items are inserted, removed or moved within the data set.

This event does not specify what about the data set has changed, forcing any observers to assume that all existing items and structure may no longer be valid. LayoutManagers will be forced to fully rebind and relayout all visible views.

RecyclerView will attempt to synthesize visible structural change events for adapters that report that they have stable IDs when this method is used. This can help for the purposes of animation and visual object persistence but individual item views will still need to be rebound and relaid out.

If you are writing an adapter it will always be more efficient to use the more specific change events if you can. Rely on notifyDataSetChanged() as a last resort.

See also
notifyItemChanged
notifyItemInserted
notifyItemRemoved
notifyItemRangeChanged
notifyItemRangeInserted
notifyItemRangeRemoved

notifyItemChanged

Added in 1.0.0
public final void notifyItemChanged(int position)

Notify any registered observers that the item at position has changed. Equivalent to calling notifyItemChanged(position, null);.

This is an item change event, not a structural change event. It indicates that any reflection of the data at position is out of date and should be updated. The item at position retains the same identity.

Parameters
int position

Position of the item that has changed
See also
notifyItemRangeChanged

notifyItemChanged

Added in 1.0.0
public final void notifyItemChanged(int position, @Nullable Object payload)

Notify any registered observers that the item at position has changed with an optional payload object.

This is an item change event, not a structural change event. It indicates that any reflection of the data at position is out of date and should be updated. The item at position retains the same identity.

Client can optionally pass a payload for partial change. These payloads will be merged and may be passed to adapter's onBindViewHolder if the item is already represented by a ViewHolder and it will be rebound to the same ViewHolder. A notifyItemRangeChanged() with null payload will clear all existing payloads on that item and prevent future payload until onBindViewHolder is called. Adapter should not assume that the payload will always be passed to onBindViewHolder(), e.g. when the view is not attached, the payload will be simply dropped.

Parameters
int position

Position of the item that has changed
@Nullable Object payload

Optional parameter, use null to identify a "full" update
See also
notifyItemRangeChanged

notifyItemInserted

Added in 1.0.0
public final void notifyItemInserted(int position)

Notify any registered observers that the item reflected at position has been newly inserted. The item previously at position is now at position position + 1.

This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.

Parameters
int position

Position of the newly inserted item in the data set
See also
notifyItemRangeInserted

notifyItemMoved

Added in 1.0.0
public final void notifyItemMoved(int fromPosition, int toPosition)

Notify any registered observers that the item reflected at fromPosition has been moved to toPosition.

This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.

Parameters
int fromPosition

Previous position of the item.
int toPosition

New position of the item.

notifyItemRangeChanged

Added in 1.0.0
public final void notifyItemRangeChanged(int positionStart, int itemCount)

Notify any registered observers that the itemCount items starting at position positionStart have changed. Equivalent to calling notifyItemRangeChanged(position, itemCount, null);.

This is an item change event, not a structural change event. It indicates that any reflection of the data in the given position range is out of date and should be updated. The items in the given range retain the same identity.

Parameters
int positionStart

Position of the first item that has changed
int itemCount

Number of items that have changed
See also
notifyItemChanged

notifyItemRangeChanged

Added in 1.0.0
public final void notifyItemRangeChanged(
    int positionStart,
    int itemCount,
    @Nullable Object payload
)

Notify any registered observers that the itemCount items starting at position positionStart have changed. An optional payload can be passed to each changed item.

This is an item change event, not a structural change event. It indicates that any reflection of the data in the given position range is out of date and should be updated. The items in the given range retain the same identity.

Client can optionally pass a payload for partial change. These payloads will be merged and may be passed to adapter's onBindViewHolder if the item is already represented by a ViewHolder and it will be rebound to the same ViewHolder. A notifyItemRangeChanged() with null payload will clear all existing payloads on that item and prevent future payload until onBindViewHolder is called. Adapter should not assume that the payload will always be passed to onBindViewHolder(), e.g. when the view is not attached, the payload will be simply dropped.

Parameters
int positionStart

Position of the first item that has changed
int itemCount

Number of items that have changed
@Nullable Object payload

Optional parameter, use null to identify a "full" update
See also
notifyItemChanged

notifyItemRangeInserted

Added in 1.0.0
public final void notifyItemRangeInserted(int positionStart, int itemCount)

Notify any registered observers that the currently reflected itemCount items starting at positionStart have been newly inserted. The items previously located at positionStart and beyond can now be found starting at position positionStart + itemCount.

This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.

Parameters
int positionStart

Position of the first item that was inserted
int itemCount

Number of items inserted
See also
notifyItemInserted

notifyItemRangeRemoved

Added in 1.0.0
public final void notifyItemRangeRemoved(int positionStart, int itemCount)

Notify any registered observers that the itemCount items previously located at positionStart have been removed from the data set. The items previously located at and after positionStart + itemCount may now be found at oldPosition - itemCount.

This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.

Parameters
int positionStart

Previous position of the first item that was removed
int itemCount

Number of items removed from the data set

notifyItemRemoved

Added in 1.0.0
public final void notifyItemRemoved(int position)

Notify any registered observers that the item previously located at position has been removed from the data set. The items previously located at and after position may now be found at oldPosition - 1.

This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.

Parameters
int position

Position of the item that has now been removed
See also
notifyItemRangeRemoved

onAttachedToRecyclerView

Added in 1.0.0
public void onAttachedToRecyclerView(@NonNull RecyclerView recyclerView)

Called by RecyclerView when it starts observing this Adapter.

Keep in mind that same adapter may be observed by multiple RecyclerViews.

Parameters
@NonNull RecyclerView recyclerView

The RecyclerView instance which started observing this adapter.
See also
onDetachedFromRecyclerView

onBindViewHolder

Added in 1.0.0
public abstract void onBindViewHolder(@NonNull VH holder, int position)

Called by RecyclerView to display the data at the specified position. This method should update the contents of the itemView to reflect the item at the given position.

Note that unlike android.widget.ListView, RecyclerView will not call this method again if the position of the item changes in the data set unless the item itself is invalidated or the new position cannot be determined. For this reason, you should only use the position parameter while acquiring the related data item inside this method and should not keep a copy of it. If you need the position of an item later on (e.g. in a click listener), use getBindingAdapterPosition which will have the updated adapter position. Override onBindViewHolder instead if Adapter can handle efficient partial bind.

Parameters
@NonNull VH holder

The ViewHolder which should be updated to represent the contents of the item at the given position in the data set.
int position

The position of the item within the adapter's data set.

onBindViewHolder

Added in 1.0.0
public void onBindViewHolder(
    @NonNull VH holder,
    int position,
    @NonNull List<Object> payloads
)

Called by RecyclerView to display the data at the specified position. This method should update the contents of the itemView to reflect the item at the given position.

Note that unlike android.widget.ListView, RecyclerView will not call this method again if the position of the item changes in the data set unless the item itself is invalidated or the new position cannot be determined. For this reason, you should only use the position parameter while acquiring the related data item inside this method and should not keep a copy of it. If you need the position of an item later on (e.g. in a click listener), use getBindingAdapterPosition which will have the updated adapter position.

Partial bind vs full bind:

The payloads parameter is a merge list from notifyItemChanged or notifyItemRangeChanged. If the payloads list is not empty, the ViewHolder is currently bound to old data and Adapter may run an efficient partial update using the payload info. If the payload is empty, Adapter must run a full bind. Adapter should not assume that the payload passed in notify methods will be received by onBindViewHolder(). For example when the view is not attached to the screen, the payload in notifyItemChange() will be simply dropped.

Parameters
@NonNull VH holder

The ViewHolder which should be updated to represent the contents of the item at the given position in the data set.
int position

The position of the item within the adapter's data set.
@NonNull List<Object> payloads

A non-null list of merged payloads. Can be empty list if requires full update.

onCreateViewHolder

Added in 1.0.0
public abstract @NonNull VH onCreateViewHolder(@NonNull ViewGroup parent, int viewType)

Called when RecyclerView needs a new ViewHolder of the given type to represent an item.

This new ViewHolder should be constructed with a new View that can represent the items of the given type. You can either create a new View manually or inflate it from an XML layout file.

The new ViewHolder will be used to display items of the adapter using onBindViewHolder. Since it will be re-used to display different items in the data set, it is a good idea to cache references to sub views of the View to avoid unnecessary findViewById calls.

Parameters
@NonNull ViewGroup parent

The ViewGroup into which the new View will be added after it is bound to an adapter position.
int viewType

The view type of the new View.
Returns
@NonNull VH

A new ViewHolder that holds a View of the given view type.
See also
getItemViewType
onBindViewHolder

onDetachedFromRecyclerView

Added in 1.0.0
public void onDetachedFromRecyclerView(@NonNull RecyclerView recyclerView)

Called by RecyclerView when it stops observing this Adapter.

Parameters
@NonNull RecyclerView recyclerView

The RecyclerView instance which stopped observing this adapter.
See also
onAttachedToRecyclerView

onFailedToRecycleView

Added in 1.0.0
public boolean onFailedToRecycleView(@NonNull VH holder)

Called by the RecyclerView if a ViewHolder created by this Adapter cannot be recycled due to its transient state. Upon receiving this callback, Adapter can clear the animation(s) that effect the View's transient state and return true so that the View can be recycled. Keep in mind that the View in question is already removed from the RecyclerView.

In some cases, it is acceptable to recycle a View although it has transient state. Most of the time, this is a case where the transient state will be cleared in onBindViewHolder call when View is rebound to a new position. For this reason, RecyclerView leaves the decision to the Adapter and uses the return value of this method to decide whether the View should be recycled or not.

Note that when all animations are created by RecyclerView.ItemAnimator, you should never receive this callback because RecyclerView keeps those Views as children until their animations are complete. This callback is useful when children of the item views create animations which may not be easy to implement using an ItemAnimator.

You should never fix this issue by calling holder.itemView.setHasTransientState(false); unless you've previously called holder.itemView.setHasTransientState(true);. Each View.setHasTransientState(true) call must be matched by a View.setHasTransientState(false) call, otherwise, the state of the View may become inconsistent. You should always prefer to end or cancel animations that are triggering the transient state instead of handling it manually.

Parameters
@NonNull VH holder

The ViewHolder containing the View that could not be recycled due to its transient state.
Returns
boolean

True if the View should be recycled, false otherwise. Note that if this method returns true, RecyclerView will ignore the transient state of the View and recycle it regardless. If this method returns false, RecyclerView will check the View's transient state again before giving a final decision. Default implementation returns false.

onViewAttachedToWindow

Added in 1.0.0
public void onViewAttachedToWindow(@NonNull VH holder)

Called when a view created by this adapter 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 those resources should be restored here.

Parameters
@NonNull VH holder

Holder of the view being attached

onViewDetachedFromWindow

Added in 1.0.0
public void onViewDetachedFromWindow(@NonNull VH holder)

Called when a view created by this adapter has been detached from its window.

Becoming detached from the window is not necessarily a permanent condition; the consumer of an Adapter's views may choose to cache views offscreen while they are not visible, attaching and detaching them as appropriate.

Parameters
@NonNull VH holder

Holder of the view being detached

onViewRecycled

Added in 1.0.0
public void onViewRecycled(@NonNull VH holder)

Called when a view created by this adapter has been recycled.

A view is recycled when a LayoutManager decides that it no longer needs to be attached to its parent RecyclerView. This can be because it has fallen out of visibility or a set of cached views represented by views still attached to the parent RecyclerView. If an item view has large or expensive data bound to it such as large bitmaps, this may be a good place to release those resources.

RecyclerView calls this method right before clearing ViewHolder's internal data and sending it to RecycledViewPool. This way, if ViewHolder was holding valid information before being recycled, you can call getBindingAdapterPosition to get its adapter position.

Parameters
@NonNull VH holder

The ViewHolder for the view being recycled

registerAdapterDataObserver

Added in 1.0.0
public void registerAdapterDataObserver(
    @NonNull RecyclerView.AdapterDataObserver observer
)

Register a new observer to listen for data changes.

The adapter may publish a variety of events describing specific changes. Not all adapters may support all change types and some may fall back to a generic "something changed" event if more specific data is not available.

Components registering observers with an adapter are responsible for unregistering those observers when finished.

Parameters
@NonNull RecyclerView.AdapterDataObserver observer

Observer to register
See also
unregisterAdapterDataObserver

setHasStableIds

Added in 1.0.0
public void setHasStableIds(boolean hasStableIds)

Indicates whether each item in the data set can be represented with a unique identifier of type java.lang.Long.

Parameters
boolean hasStableIds

Whether items in data set have unique identifiers or not.
See also
hasStableIds
getItemId

setStateRestorationPolicy

Added in 1.2.0
public void setStateRestorationPolicy(
    @NonNull RecyclerView.Adapter.StateRestorationPolicy strategy
)

Sets the state restoration strategy for the Adapter. By default, it is set to ALLOW which means RecyclerView expects any set Adapter to be immediately capable of restoring the RecyclerView's saved scroll position.

This behaviour might be undesired if the Adapter's data is loaded asynchronously, and thus unavailable during initial layout (e.g. after Activity rotation). To avoid losing scroll position, you can change this to be either PREVENT_WHEN_EMPTY or PREVENT. Note that the former means your RecyclerView will restore state as soon as Adapter has 1 or more items while the latter requires you to call setStateRestorationPolicy with either ALLOW or PREVENT_WHEN_EMPTY again when the Adapter is ready to restore its state.

RecyclerView will still layout even when State restoration is disabled. The behavior of how State is restored is up to the LayoutManager. All default LayoutManagers will override current state with restored state when state restoration happens (unless an explicit call to scrollToPosition is made).

Calling this method after state is restored will not have any effect other than changing the return value of getStateRestorationPolicy.

Parameters
@NonNull RecyclerView.Adapter.StateRestorationPolicy strategy

The saved state restoration strategy for this Adapter.
See also
getStateRestorationPolicy

unregisterAdapterDataObserver

Added in 1.0.0
public void unregisterAdapterDataObserver(
    @NonNull RecyclerView.AdapterDataObserver observer
)

Unregister an observer currently listening for data changes.

The unregistered observer will no longer receive events about changes to the adapter.

Parameters
@NonNull RecyclerView.AdapterDataObserver observer

Observer to unregister
See also
registerAdapterDataObserver