RecyclerView.ItemAnimator

public abstract class RecyclerView.ItemAnimator

Known direct subclasses
SimpleItemAnimator

A wrapper class for ItemAnimator that records View bounds and decides whether it should run move, change, add or remove animations.
Known indirect subclasses
DefaultItemAnimator

This implementation of RecyclerView.ItemAnimator provides basic animations on remove, add, and move events that happen to the items in a RecyclerView.

This class defines the animations that take place on items as changes are made to the adapter. Subclasses of ItemAnimator can be used to implement custom animations for actions on ViewHolder items. The RecyclerView will manage retaining these items while they are being animated, but implementors must call dispatchAnimationFinished when a ViewHolder's animation is finished. In other words, there must be a matching dispatchAnimationFinished call for each animateAppearance(), animateChange()animatePersistence(), and animateDisappearance() call.

By default, RecyclerView uses DefaultItemAnimator.

See also
setItemAnimator

Summary

Nested types
@IntDef(flag = true, value = )
@Retention(value = RetentionPolicy.SOURCE)
public annotation RecyclerView.ItemAnimator.AdapterChanges

The set of flags that might be passed to recordPreLayoutInformation.

This interface is used to inform listeners when all pending or running animations in an ItemAnimator are finished.

A simple data structure that holds information about an item's bounds.

Constants
static final int

This ViewHolder was not laid out but has been added to the layout in pre-layout state by the LayoutManager.
static final int

The Item represented by this ViewHolder is updated.
static final int

Adapter notifyDataSetChanged has been called and the content represented by this ViewHolder is invalid.
static final int
FLAG_MOVED = 2048

The position of the Item represented by this ViewHolder has been changed.
static final int

The Item represented by this ViewHolder is removed from the adapter.

Public constructors

Public methods
abstract boolean

Called by the RecyclerView when a ViewHolder is added to the layout.
abstract boolean

Called by the RecyclerView when an adapter item is present both before and after the layout and RecyclerView has received a notifyItemChanged call for it.
abstract boolean

Called by the RecyclerView when a ViewHolder has disappeared from the layout.
abstract boolean

Called by the RecyclerView when a ViewHolder is present in both before and after the layout and RecyclerView has not received a notifyItemChanged call for it or a notifyDataSetChanged call.
boolean

When an item is changed, ItemAnimator can decide whether it wants to re-use the same ViewHolder for animations or RecyclerView should create a copy of the item and ItemAnimator will use both to run the animation (e.g. cross-fade).
boolean

When an item is changed, ItemAnimator can decide whether it wants to re-use the same ViewHolder for animations or RecyclerView should create a copy of the item and ItemAnimator will use both to run the animation (e.g. cross-fade).
final void

Method to be called by subclasses when an animation is finished.
final void

Method to be called by subclasses when an animation is started.
final void

This method should be called by ItemAnimator implementations to notify any listeners that all pending and active item animations are finished.
abstract void

Method called when an animation on a view should be ended immediately.
abstract void

Method called when all item animations should be ended immediately.
long

Gets the current duration for which all add animations will run.
long

Gets the current duration for which all change animations will run.
long

Gets the current duration for which all move animations will run.
long

Gets the current duration for which all remove animations will run.
abstract boolean

Method which returns whether there are any item animations currently running.
final boolean

Like isRunning, this method returns whether there are any item animations currently running.
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo

Returns a new ItemHolderInfo which will be used to store information about the ViewHolder.
void

Called after dispatchAnimationFinished is called by the ItemAnimator.
void

Called when a new animation is started on the given ViewHolder.
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo

Called by the RecyclerView after the layout is complete.
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo
recordPreLayoutInformation(
    @NonNull RecyclerView.State state,
    @NonNull RecyclerView.ViewHolder viewHolder,
    @RecyclerView.ItemAnimator.AdapterChanges int changeFlags,
    @NonNull List<Object> payloads
)

Called by the RecyclerView before the layout begins.
abstract void

Called when there are pending animations waiting to be started.
void
setAddDuration(long addDuration)

Sets the duration for which all add animations will run.
void
setChangeDuration(long changeDuration)

Sets the duration for which all change animations will run.
void
setMoveDuration(long moveDuration)

Sets the duration for which all move animations will run.
void
setRemoveDuration(long removeDuration)

Sets the duration for which all remove animations will run.

Constants

FLAG_APPEARED_IN_PRE_LAYOUT

Added in 1.0.0
public static final int FLAG_APPEARED_IN_PRE_LAYOUT = 4096

This ViewHolder was not laid out but has been added to the layout in pre-layout state by the LayoutManager. This means that the item was already in the Adapter but invisible and it may become visible in the post layout phase. LayoutManagers may prefer to add new items in pre-layout to specify their virtual location when they are invisible (e.g. to specify the item should animate in from below the visible area).

See also
recordPreLayoutInformation

FLAG_CHANGED

Added in 1.0.0
public static final int FLAG_CHANGED = 2

The Item represented by this ViewHolder is updated.

See also
recordPreLayoutInformation

FLAG_INVALIDATED

Added in 1.0.0
public static final int FLAG_INVALIDATED = 4

Adapter notifyDataSetChanged has been called and the content represented by this ViewHolder is invalid.

See also
recordPreLayoutInformation

FLAG_MOVED

Added in 1.0.0
public static final int FLAG_MOVED = 2048

The position of the Item represented by this ViewHolder has been changed. This flag is not bound to notifyItemMoved. It might be set in response to any adapter change that may have a side effect on this item. (e.g. The item before this one has been removed from the Adapter).

See also
recordPreLayoutInformation

FLAG_REMOVED

Added in 1.0.0
public static final int FLAG_REMOVED = 8

The Item represented by this ViewHolder is removed from the adapter.

See also
recordPreLayoutInformation

Public constructors

ItemAnimator

Added in 1.0.0
public ItemAnimator()

Public methods

animateAppearance

Added in 1.0.0
public abstract boolean animateAppearance(
    @NonNull RecyclerView.ViewHolder viewHolder,
    @Nullable RecyclerView.ItemAnimator.ItemHolderInfo preLayoutInfo,
    @NonNull RecyclerView.ItemAnimator.ItemHolderInfo postLayoutInfo
)

Called by the RecyclerView when a ViewHolder is added to the layout.

In detail, this means that the ViewHolder was not a child when the layout started but has been added by the LayoutManager. It might be newly added to the adapter or simply become visible due to other factors.

ItemAnimator must call dispatchAnimationFinished when the animation is complete (or instantly call dispatchAnimationFinished if it decides not to animate the view).

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder which should be animated
@Nullable RecyclerView.ItemAnimator.ItemHolderInfo preLayoutInfo

The information that was returned from recordPreLayoutInformation. Might be null if Item was just added to the adapter or LayoutManager does not support predictive animations or it could not predict that this ViewHolder will become visible.
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo postLayoutInfo

The information that was returned from recordPreLayoutInformation.
Returns
boolean

true if a later call to runPendingAnimations is requested, false otherwise.

animateChange

Added in 1.0.0
public abstract boolean animateChange(
    @NonNull RecyclerView.ViewHolder oldHolder,
    @NonNull RecyclerView.ViewHolder newHolder,
    @NonNull RecyclerView.ItemAnimator.ItemHolderInfo preLayoutInfo,
    @NonNull RecyclerView.ItemAnimator.ItemHolderInfo postLayoutInfo
)

Called by the RecyclerView when an adapter item is present both before and after the layout and RecyclerView has received a notifyItemChanged call for it. This method may also be called when notifyDataSetChanged is called and adapter has stable ids so that RecyclerView could still rebind views to the same ViewHolders. If viewType changes when notifyDataSetChanged is called, this method will not be called, instead, animateAppearance will be called for the new ViewHolder and the old one will be recycled.

If this method is called due to a notifyDataSetChanged call, there is a good possibility that item contents didn't really change but it is rebound from the adapter. DefaultItemAnimator will skip animating the View if its location on the screen didn't change and your animator should handle this case as well and avoid creating unnecessary animations.

When an item is updated, ItemAnimator has a chance to ask RecyclerView to keep the previous presentation of the item as-is and supply a new ViewHolder for the updated presentation (see: canReuseUpdatedViewHolder. This is useful if you don't know the contents of the Item and would like to cross-fade the old and the new one (DefaultItemAnimator uses this technique).

When you are writing a custom item animator for your layout, it might be more performant and elegant to re-use the same ViewHolder and animate the content changes manually.

When notifyItemChanged is called, the Item's view type may change. If the Item's view type has changed or ItemAnimator returned false for this ViewHolder when canReuseUpdatedViewHolder was called, the oldHolder and newHolder will be different ViewHolder instances which represent the same Item. In that case, only the new ViewHolder is visible to the LayoutManager but RecyclerView keeps old ViewHolder attached for animations.

ItemAnimator must call dispatchAnimationFinished for each distinct ViewHolder when their animation is complete (or instantly call dispatchAnimationFinished if it decides not to animate the view).

If oldHolder and newHolder are the same instance, you should call dispatchAnimationFinishedonly once.

Note that when a ViewHolder both changes and disappears in the same layout pass, the animation callback method which will be called by the RecyclerView depends on the ItemAnimator's decision whether to re-use the same ViewHolder or not, and also the LayoutManager's decision whether to layout the changed version of a disappearing ViewHolder or not. RecyclerView will call animateChange instead of animateDisappearance if and only if the ItemAnimator returns false from canReuseUpdatedViewHolder and the LayoutManager lays out a new disappearing view that holds the updated information. Built-in LayoutManagers try to avoid laying out updated versions of disappearing views.

Parameters
@NonNull RecyclerView.ViewHolder oldHolder

The ViewHolder before the layout is started, might be the same instance with newHolder.
@NonNull RecyclerView.ViewHolder newHolder

The ViewHolder after the layout is finished, might be the same instance with oldHolder.
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo preLayoutInfo

The information that was returned from recordPreLayoutInformation.
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo postLayoutInfo

The information that was returned from recordPreLayoutInformation.
Returns
boolean

true if a later call to runPendingAnimations is requested, false otherwise.

animateDisappearance

Added in 1.0.0
public abstract boolean animateDisappearance(
    @NonNull RecyclerView.ViewHolder viewHolder,
    @NonNull RecyclerView.ItemAnimator.ItemHolderInfo preLayoutInfo,
    @Nullable RecyclerView.ItemAnimator.ItemHolderInfo postLayoutInfo
)

Called by the RecyclerView when a ViewHolder has disappeared from the layout.

This means that the View was a child of the LayoutManager when layout started but has been removed by the LayoutManager. It might have been removed from the adapter or simply become invisible due to other factors. You can distinguish these two cases by checking the change flags that were passed to recordPreLayoutInformation.

Note that when a ViewHolder both changes and disappears in the same layout pass, the animation callback method which will be called by the RecyclerView depends on the ItemAnimator's decision whether to re-use the same ViewHolder or not, and also the LayoutManager's decision whether to layout the changed version of a disappearing ViewHolder or not. RecyclerView will call animateChange instead of animateDisappearance if and only if the ItemAnimator returns false from canReuseUpdatedViewHolder and the LayoutManager lays out a new disappearing view that holds the updated information. Built-in LayoutManagers try to avoid laying out updated versions of disappearing views.

If LayoutManager supports predictive animations, it might provide a target disappear location for the View by laying it out in that location. When that happens, RecyclerView will call recordPostLayoutInformation and the response of that call will be passed to this method as the postLayoutInfo.

ItemAnimator must call dispatchAnimationFinished when the animation is complete (or instantly call dispatchAnimationFinished if it decides not to animate the view).

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder which should be animated
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo preLayoutInfo

The information that was returned from recordPreLayoutInformation.
@Nullable RecyclerView.ItemAnimator.ItemHolderInfo postLayoutInfo

The information that was returned from recordPostLayoutInformation. Might be null if the LayoutManager did not layout the item.
Returns
boolean

true if a later call to runPendingAnimations is requested, false otherwise.

animatePersistence

Added in 1.0.0
public abstract boolean animatePersistence(
    @NonNull RecyclerView.ViewHolder viewHolder,
    @NonNull RecyclerView.ItemAnimator.ItemHolderInfo preLayoutInfo,
    @NonNull RecyclerView.ItemAnimator.ItemHolderInfo postLayoutInfo
)

Called by the RecyclerView when a ViewHolder is present in both before and after the layout and RecyclerView has not received a notifyItemChanged call for it or a notifyDataSetChanged call.

This ViewHolder still represents the same data that it was representing when the layout started but its position / size may be changed by the LayoutManager.

If the Item's layout position didn't change, RecyclerView still calls this method because it does not track this information (or does not necessarily know that an animation is not required). Your ItemAnimator should handle this case and if there is nothing to animate, it should call dispatchAnimationFinished and return false.

ItemAnimator must call dispatchAnimationFinished when the animation is complete (or instantly call dispatchAnimationFinished if it decides not to animate the view).

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder which should be animated
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo preLayoutInfo

The information that was returned from recordPreLayoutInformation.
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo postLayoutInfo

The information that was returned from recordPreLayoutInformation.
Returns
boolean

true if a later call to runPendingAnimations is requested, false otherwise.

canReuseUpdatedViewHolder

Added in 1.0.0
public boolean canReuseUpdatedViewHolder(@NonNull RecyclerView.ViewHolder viewHolder)

When an item is changed, ItemAnimator can decide whether it wants to re-use the same ViewHolder for animations or RecyclerView should create a copy of the item and ItemAnimator will use both to run the animation (e.g. cross-fade).

Note that this method will only be called if the ViewHolder still has the same type (getItemViewType). Otherwise, ItemAnimator will always receive both ViewHolders in the animateChange method.

If your application is using change payloads, you can override canReuseUpdatedViewHolder to decide based on payloads.

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder which represents the changed item's old content.
Returns
boolean

True if RecyclerView should just rebind to the same ViewHolder or false if RecyclerView should create a new ViewHolder and pass this ViewHolder to the ItemAnimator to animate. Default implementation returns true.
See also
canReuseUpdatedViewHolder

canReuseUpdatedViewHolder

Added in 1.0.0
public boolean canReuseUpdatedViewHolder(
    @NonNull RecyclerView.ViewHolder viewHolder,
    @NonNull List<Object> payloads
)

When an item is changed, ItemAnimator can decide whether it wants to re-use the same ViewHolder for animations or RecyclerView should create a copy of the item and ItemAnimator will use both to run the animation (e.g. cross-fade).

Note that this method will only be called if the ViewHolder still has the same type (getItemViewType). Otherwise, ItemAnimator will always receive both ViewHolders in the animateChange method.

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder which represents the changed item's old content.
@NonNull List<Object> payloads

A non-null list of merged payloads that were sent with change notifications. Can be empty if the adapter is invalidated via notifyDataSetChanged. The same list of payloads will be passed into onBindViewHolder method if this method returns true.
Returns
boolean

True if RecyclerView should just rebind to the same ViewHolder or false if RecyclerView should create a new ViewHolder and pass this ViewHolder to the ItemAnimator to animate. Default implementation calls canReuseUpdatedViewHolder.
See also
canReuseUpdatedViewHolder

dispatchAnimationFinished

Added in 1.0.0
public final void dispatchAnimationFinished(@NonNull RecyclerView.ViewHolder viewHolder)

Method to be called by subclasses when an animation is finished.

For each call RecyclerView makes to animateAppearance(), animatePersistence(), or animateDisappearance(), there should be a matching dispatchAnimationFinished call by the subclass.

For animateChange(), subclass should call this method for both the oldHolder and newHolder (if they are not the same instance).

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder whose animation is finished.
See also
onAnimationFinished

dispatchAnimationStarted

Added in 1.0.0
public final void dispatchAnimationStarted(@NonNull RecyclerView.ViewHolder viewHolder)

Method to be called by subclasses when an animation is started.

For each call RecyclerView makes to animateAppearance(), animatePersistence(), or animateDisappearance(), there should be a matching dispatchAnimationStarted call by the subclass.

For animateChange(), subclass should call this method for both the oldHolder and newHolder (if they are not the same instance).

If your ItemAnimator decides not to animate a ViewHolder, it should call dispatchAnimationFinishedwithout calling dispatchAnimationStarted.

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder whose animation is starting.
See also
onAnimationStarted

dispatchAnimationsFinished

Added in 1.0.0
public final void dispatchAnimationsFinished()

This method should be called by ItemAnimator implementations to notify any listeners that all pending and active item animations are finished.

endAnimation

Added in 1.0.0
public abstract void endAnimation(@NonNull RecyclerView.ViewHolder item)

Method called when an animation on a view should be ended immediately. This could happen when other events, like scrolling, occur, so that animating views can be quickly put into their proper end locations. Implementations should ensure that any animations running on the item are canceled and affected properties are set to their end values. Also, dispatchAnimationFinished should be called for each finished animation since the animations are effectively done when this method is called.

Parameters
@NonNull RecyclerView.ViewHolder item

The item for which an animation should be stopped.

endAnimations

Added in 1.0.0
public abstract void endAnimations()

Method called when all item animations should be ended immediately. This could happen when other events, like scrolling, occur, so that animating views can be quickly put into their proper end locations. Implementations should ensure that any animations running on any items are canceled and affected properties are set to their end values. Also, dispatchAnimationFinished should be called for each finished animation since the animations are effectively done when this method is called.

getAddDuration

Added in 1.0.0
public long getAddDuration()

Gets the current duration for which all add animations will run.

Returns
long

The current add duration

getChangeDuration

Added in 1.0.0
public long getChangeDuration()

Gets the current duration for which all change animations will run.

Returns
long

The current change duration

getMoveDuration

Added in 1.0.0
public long getMoveDuration()

Gets the current duration for which all move animations will run.

Returns
long

The current move duration

getRemoveDuration

Added in 1.0.0
public long getRemoveDuration()

Gets the current duration for which all remove animations will run.

Returns
long

The current remove duration

isRunning

Added in 1.0.0
public abstract boolean isRunning()

Method which returns whether there are any item animations currently running. This method can be used to determine whether to delay other actions until animations end.

Returns
boolean

true if there are any item animations currently running, false otherwise.

isRunning

Added in 1.0.0
public final boolean isRunning(
    @Nullable RecyclerView.ItemAnimator.ItemAnimatorFinishedListener listener
)

Like isRunning, this method returns whether there are any item animations currently running. Additionally, the listener passed in will be called when there are no item animations running, either immediately (before the method returns) if no animations are currently running, or when the currently running animations are finished.

Note that the listener is transient - it is either called immediately and not stored at all, or stored only until it is called when running animations are finished sometime later.

Parameters
@Nullable RecyclerView.ItemAnimator.ItemAnimatorFinishedListener listener

A listener to be called immediately if no animations are running or later when currently-running animations have finished. A null listener is equivalent to calling isRunning.
Returns
boolean

true if there are any item animations currently running, false otherwise.

obtainHolderInfo

Added in 1.0.0
public @NonNull RecyclerView.ItemAnimator.ItemHolderInfo obtainHolderInfo()

Returns a new ItemHolderInfo which will be used to store information about the ViewHolder. This information will later be passed into animate** methods.

You can override this method if you want to extend ItemHolderInfo and provide your own instances.

Returns
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo

A new ItemHolderInfo.

onAnimationFinished

Added in 1.0.0
public void onAnimationFinished(@NonNull RecyclerView.ViewHolder viewHolder)

Called after dispatchAnimationFinished is called by the ItemAnimator.

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder whose animation is finished. There might still be other animations running on this ViewHolder.
See also
dispatchAnimationFinished

onAnimationStarted

Added in 1.0.0
public void onAnimationStarted(@NonNull RecyclerView.ViewHolder viewHolder)

Called when a new animation is started on the given ViewHolder.

Parameters
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder which started animating. Note that the ViewHolder might already be animating and this might be another animation.
See also
dispatchAnimationStarted

recordPostLayoutInformation

Added in 1.0.0
public @NonNull RecyclerView.ItemAnimator.ItemHolderInfo recordPostLayoutInformation(
    @NonNull RecyclerView.State state,
    @NonNull RecyclerView.ViewHolder viewHolder
)

Called by the RecyclerView after the layout is complete. Item animator should record necessary information about the View's final state.

The data returned from this method will be passed to the related animate** methods.

The default implementation returns an ItemHolderInfo which holds the bounds of the View.

Parameters
@NonNull RecyclerView.State state

The current State of RecyclerView which includes some useful data about the layout that will be calculated.
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder whose information should be recorded.
Returns
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo

An ItemHolderInfo that preserves necessary information about the ViewHolder. This object will be passed back to related animate** methods when RecyclerView decides how items should be animated.
See also
recordPreLayoutInformation
animateAppearance
animateDisappearance
animateChange
animatePersistence

recordPreLayoutInformation

Added in 1.0.0
public @NonNull RecyclerView.ItemAnimator.ItemHolderInfo recordPreLayoutInformation(
    @NonNull RecyclerView.State state,
    @NonNull RecyclerView.ViewHolder viewHolder,
    @RecyclerView.ItemAnimator.AdapterChanges int changeFlags,
    @NonNull List<Object> payloads
)

Called by the RecyclerView before the layout begins. Item animator should record necessary information about the View before it is potentially rebound, moved or removed.

The data returned from this method will be passed to the related animate** methods.

Note that this method may be called after pre-layout phase if LayoutManager adds new Views to the layout in pre-layout pass.

The default implementation returns an ItemHolderInfo which holds the bounds of the View and the adapter change flags.

Parameters
@NonNull RecyclerView.State state

The current State of RecyclerView which includes some useful data about the layout that will be calculated.
@NonNull RecyclerView.ViewHolder viewHolder

The ViewHolder whose information should be recorded.
@RecyclerView.ItemAnimator.AdapterChanges int changeFlags

Additional information about what changes happened in the Adapter about the Item represented by this ViewHolder. For instance, if item is deleted from the adapter, FLAG_REMOVED will be set.
@NonNull List<Object> payloads

The payload list that was previously passed to notifyItemChanged or notifyItemRangeChanged.
Returns
@NonNull RecyclerView.ItemAnimator.ItemHolderInfo

An ItemHolderInfo instance that preserves necessary information about the ViewHolder. This object will be passed back to related animate** methods after layout is complete.
See also
recordPostLayoutInformation
animateAppearance
animateDisappearance
animateChange
animatePersistence

runPendingAnimations

Added in 1.0.0
public abstract void runPendingAnimations()

Called when there are pending animations waiting to be started. This state is governed by the return values from animateAppearance(), animateChange()animatePersistence(), and animateDisappearance(), which inform the RecyclerView that the ItemAnimator wants to be called later to start the associated animations. runPendingAnimations() will be scheduled to be run on the next frame.

setAddDuration

Added in 1.0.0
public void setAddDuration(long addDuration)

Sets the duration for which all add animations will run.

Parameters
long addDuration

The add duration

setChangeDuration

Added in 1.0.0
public void setChangeDuration(long changeDuration)

Sets the duration for which all change animations will run.

Parameters
long changeDuration

The change duration

setMoveDuration

Added in 1.0.0
public void setMoveDuration(long moveDuration)

Sets the duration for which all move animations will run.

Parameters
long moveDuration

The move duration

setRemoveDuration

Added in 1.0.0
public void setRemoveDuration(long removeDuration)

Sets the duration for which all remove animations will run.

Parameters
long removeDuration

The remove duration