DefaultItemAnimator

Called when an item is added to the RecyclerView. Implementors can choose whether and how to animate that change, but must always call dispatchAddFinished(ViewHolder) when done, either immediately (if no animation will occur) or after the animation actually finishes. The return value indicates whether an animation has been set up and whether the ItemAnimator's runPendingAnimations() method should be called at the next opportunity. This mechanism allows ItemAnimator to set up individual animations as separate calls to animateAdd(), animateMove(), animateRemove(), and animateChange(ViewHolder, ViewHolder, int, int, int, int) come in one by one, then start the animations together in the later call to runPendingAnimations().

This method may also be called for appearing items which were already in the RecyclerView, but for which the system does not have enough information to animate them into view. In that case, the default animation for adding items is run on those items as well.

Called when an item is changed in the RecyclerView, as indicated by a call to notifyItemChanged(int) or notifyItemRangeChanged(int, int).

Implementers can choose whether and how to animate changes, but must always call dispatchChangeFinished(ViewHolder, boolean) for each non-null ViewHolder, either immediately (if no animation will occur) or after the animation actually finishes. The return value indicates whether an animation has been set up and whether the ItemAnimator's runPendingAnimations() method should be called at the next opportunity. This mechanism allows ItemAnimator to set up individual animations as separate calls to animateAdd(), animateMove(), animateRemove(), and animateChange(ViewHolder, ViewHolder, int, int, int, int) come in one by one, then start the animations together in the later call to runPendingAnimations().

Called when an item is moved in the RecyclerView. Implementors can choose whether and how to animate that change, but must always call dispatchMoveFinished(ViewHolder) when done, either immediately (if no animation will occur) or after the animation actually finishes. The return value indicates whether an animation has been set up and whether the ItemAnimator's runPendingAnimations() method should be called at the next opportunity. This mechanism allows ItemAnimator to set up individual animations as separate calls to animateAdd(), animateMove(), animateRemove(), and animateChange(ViewHolder, ViewHolder, int, int, int, int) come in one by one, then start the animations together in the later call to runPendingAnimations().

Called when an item is removed from the RecyclerView. Implementors can choose whether and how to animate that change, but must always call dispatchRemoveFinished(ViewHolder) when done, either immediately (if no animation will occur) or after the animation actually finishes. The return value indicates whether an animation has been set up and whether the ItemAnimator's runPendingAnimations() method should be called at the next opportunity. This mechanism allows ItemAnimator to set up individual animations as separate calls to animateAdd(), animateMove(), animateRemove(), and animateChange(ViewHolder, ViewHolder, int, int, int, int) come in one by one, then start the animations together in the later call to runPendingAnimations().

This method may also be called for disappearing items which continue to exist in the RecyclerView, but for which the system does not have enough information to animate them out of view. In that case, the default animation for removing items is run on those items as well.

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, appropriate dispatch methods (e.g., dispatchAddFinished(ViewHolder) should be called since the animations are effectively done when this method is called.

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, appropriate dispatch methods (e.g., dispatchAddFinished(ViewHolder) should be called since the animations are effectively done when this method is called.

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.

Called when there are pending animations waiting to be started. This state is governed by the return values from animateAdd(), animateMove(), and animateRemove(), 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.