added in version 24.1.0
belongs to Maven artifact


public static abstract class ItemTouchHelper.Callback
extends Object

Known Direct Subclasses

This class is the contract between ItemTouchHelper and your application. It lets you control which touch behaviors are enabled per each ViewHolder and also receive callbacks when user performs these actions.

To control which actions user can take on each view, you should override getMovementFlags(RecyclerView, ViewHolder) and return appropriate set of direction flags. (LEFT, RIGHT, START, END, UP, DOWN). You can use makeMovementFlags(int, int) to easily construct it. Alternatively, you can use ItemTouchHelper.SimpleCallback.

If user drags an item, ItemTouchHelper will call onMove(recyclerView, dragged, target). Upon receiving this callback, you should move the item from the old position (dragged.getAdapterPosition()) to new position (target.getAdapterPosition()) in your adapter and also call notifyItemMoved(int, int). To control where a View can be dropped, you can override canDropOver(RecyclerView, ViewHolder, ViewHolder). When a dragging View overlaps multiple other views, Callback chooses the closest View with which dragged View might have changed positions. Although this approach works for many use cases, if you have a custom LayoutManager, you can override chooseDropTarget(ViewHolder, java.util.List, int, int) to select a custom drop target.

When a View is swiped, ItemTouchHelper animates it until it goes out of bounds, then calls onSwiped(ViewHolder, int). At this point, you should update your adapter (e.g. remove the item) and call related Adapter#notify event.





Public constructors


Public methods

boolean canDropOver(RecyclerView recyclerView, RecyclerView.ViewHolder current, RecyclerView.ViewHolder target)

Return true if the current ViewHolder can be dropped over the the target ViewHolder.

RecyclerView.ViewHolder chooseDropTarget(RecyclerView.ViewHolder selected, List<RecyclerView.ViewHolder> dropTargets, int curX, int curY)

Called by ItemTouchHelper to select a drop target from the list of ViewHolders that are under the dragged View.

void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder)

Called by the ItemTouchHelper when the user interaction with an element is over and it also completed its animation.

int convertToAbsoluteDirection(int flags, int layoutDirection)

Converts a given set of flags to absolution direction which means START and END are replaced with LEFT and RIGHT depending on the layout direction.

static int convertToRelativeDirection(int flags, int layoutDirection)

Replaces a movement direction with its relative version by taking layout direction into account.

long getAnimationDuration(RecyclerView recyclerView, int animationType, float animateDx, float animateDy)

Called by the ItemTouchHelper when user action finished on a ViewHolder and now the View will be animated to its final position.

int getBoundingBoxMargin()

When finding views under a dragged view, by default, ItemTouchHelper searches for views that overlap with the dragged View.

static ItemTouchUIUtil getDefaultUIUtil()

Returns the