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ItemTouchHelper

public class ItemTouchHelper
extends RecyclerView.ItemDecoration implements RecyclerView.OnChildAttachStateChangeListener

java.lang.Object
   ↳ android.support.v7.widget.RecyclerView.ItemDecoration
     ↳ android.support.v7.widget.helper.ItemTouchHelper


This is a utility class to add swipe to dismiss and drag & drop support to RecyclerView.

It works with a RecyclerView and a Callback class, which configures what type of interactions are enabled and also receives events when user performs these actions.

Depending on which functionality you support, you should override onMove(RecyclerView, ViewHolder, ViewHolder) and / or onSwiped(ViewHolder, int).

This class is designed to work with any LayoutManager but for certain situations, it can be optimized for your custom LayoutManager by extending methods in the ItemTouchHelper.Callback class or implementing ItemTouchHelper.ViewDropHandler interface in your LayoutManager.

By default, ItemTouchHelper moves the items' translateX/Y properties to reposition them. You can customize these behaviors by overriding onChildDraw(Canvas, RecyclerView, ViewHolder, float, float, int, boolean) or onChildDrawOver(Canvas, RecyclerView, ViewHolder, float, float, int, boolean).

Most of the time you only need to override onChildDraw.

Summary

Nested classes

class ItemTouchHelper.Callback

This class is the contract between ItemTouchHelper and your application. 

class ItemTouchHelper.SimpleCallback

A simple wrapper to the default Callback which you can construct with drag and swipe directions and this class will handle the flag callbacks. 

interface ItemTouchHelper.ViewDropHandler

An interface which can be implemented by LayoutManager for better integration with ItemTouchHelper

Constants

int ACTION_STATE_DRAG

A View is currently being dragged.

int ACTION_STATE_IDLE

ItemTouchHelper is in idle state.

int ACTION_STATE_SWIPE

A View is currently being swiped.

int ANIMATION_TYPE_DRAG

Animation type for views that were dragged and now will animate to their final position.

int ANIMATION_TYPE_SWIPE_CANCEL

Animation type for views which are not completely swiped thus will animate back to their original position.

int ANIMATION_TYPE_SWIPE_SUCCESS

Animation type for views which are swiped successfully.

int DOWN

Down direction, used for swipe & drag control.

int END

Horizontal end direction.

int LEFT

Left direction, used for swipe & drag control.

int RIGHT

Right direction, used for swipe & drag control.

int START

Horizontal start direction.

int UP

Up direction, used for swipe & drag control.

Public constructors

ItemTouchHelper(ItemTouchHelper.Callback callback)

Creates an ItemTouchHelper that will work with the given Callback.

Public methods

void attachToRecyclerView(RecyclerView recyclerView)

Attaches the ItemTouchHelper to the provided RecyclerView.

void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state)

Retrieve any offsets for the given item.

void onChildViewAttachedToWindow(View view)

Called when a view is attached to the RecyclerView.

void onChildViewDetachedFromWindow(View view)

Called when a view is detached from RecyclerView.

void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state)

Draw any appropriate decorations into the Canvas supplied to the RecyclerView.

void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state)

Draw any appropriate decorations into the Canvas supplied to the RecyclerView.

void startDrag(RecyclerView.ViewHolder viewHolder)

Starts dragging the provided ViewHolder.

void startSwipe(RecyclerView.ViewHolder viewHolder)

Starts swiping the provided ViewHolder.

Inherited methods

From class android.support.v7.widget.RecyclerView.ItemDecoration
From class java.lang.Object
From interface android.support.v7.widget.RecyclerView.OnChildAttachStateChangeListener

Constants

ACTION_STATE_DRAG

added in version 22.2.0
int ACTION_STATE_DRAG

A View is currently being dragged.

Constant Value: 2 (0x00000002)

ACTION_STATE_IDLE

added in version 22.2.0
int ACTION_STATE_IDLE

ItemTouchHelper is in idle state. At this state, either there is no related motion event by the user or latest motion events have not yet triggered a swipe or drag.

Constant Value: 0 (0x00000000)

ACTION_STATE_SWIPE

added in version 22.2.0
int ACTION_STATE_SWIPE

A View is currently being swiped.

Constant Value: 1 (0x00000001)

ANIMATION_TYPE_DRAG

added in version 22.2.0
int ANIMATION_TYPE_DRAG

Animation type for views that were dragged and now will animate to their final position.

Constant Value: 8 (0x00000008)

ANIMATION_TYPE_SWIPE_CANCEL

added in version 22.2.0
int ANIMATION_TYPE_SWIPE_CANCEL

Animation type for views which are not completely swiped thus will animate back to their original position.

Constant Value: 4 (0x00000004)

ANIMATION_TYPE_SWIPE_SUCCESS

added in version 22.2.0
int ANIMATION_TYPE_SWIPE_SUCCESS

Animation type for views which are swiped successfully.

Constant Value: 2 (0x00000002)

DOWN

added in version 22.2.0
int DOWN

Down direction, used for swipe & drag control.

Constant Value: 2 (0x00000002)

END

added in version 22.2.0
int END

Horizontal end direction. Resolved to LEFT or RIGHT depending on RecyclerView's layout direction. Used for swipe & drag control.

Constant Value: 32 (0x00000020)

LEFT

added in version 22.2.0
int LEFT

Left direction, used for swipe & drag control.

Constant Value: 4 (0x00000004)

RIGHT

added in version 22.2.0
int RIGHT

Right direction, used for swipe & drag control.

Constant Value: 8 (0x00000008)

START

added in version 22.2.0
int START

Horizontal start direction. Resolved to LEFT or RIGHT depending on RecyclerView's layout direction. Used for swipe & drag control.

Constant Value: 16 (0x00000010)

UP

added in version 22.2.0
int UP

Up direction, used for swipe & drag control.

Constant Value: 1 (0x00000001)

Public constructors

ItemTouchHelper

added in version 22.2.0
ItemTouchHelper (ItemTouchHelper.Callback callback)

Creates an ItemTouchHelper that will work with the given Callback.

You can attach ItemTouchHelper to a RecyclerView via attachToRecyclerView(RecyclerView). Upon attaching, it will add an item decoration, an onItemTouchListener and a Child attach / detach listener to the RecyclerView.

Parameters
callback ItemTouchHelper.Callback: The Callback which controls the behavior of this touch helper.

Public methods

attachToRecyclerView

added in version 22.2.0
void attachToRecyclerView (RecyclerView recyclerView)

Attaches the ItemTouchHelper to the provided RecyclerView. If TouchHelper is already attached to a RecyclerView, it will first detach from the previous one. You can call this method with null to detach it from the current RecyclerView.

Parameters
recyclerView RecyclerView: The RecyclerView instance to which you want to add this helper or null if you want to remove ItemTouchHelper from the current RecyclerView.

getItemOffsets

added in version 22.2.0
void getItemOffsets (Rect outRect, 
                View view, 
                RecyclerView parent, 
                RecyclerView.State state)

Retrieve any offsets for the given item. Each field of outRect specifies the number of pixels that the item view should be inset by, similar to padding or margin. The default implementation sets the bounds of outRect to 0 and returns.

If this ItemDecoration does not affect the positioning of item views, it should set all four fields of outRect (left, top, right, bottom) to zero before returning.

If you need to access Adapter for additional data, you can call getChildAdapterPosition(View) to get the adapter position of the View.

Parameters
outRect Rect: Rect to receive the output.
view View: The child view to decorate
parent RecyclerView: RecyclerView this ItemDecoration is decorating
state RecyclerView.State: The current state of RecyclerView.

onChildViewAttachedToWindow

added in version 22.2.0
void onChildViewAttachedToWindow (View view)

Called when a view is attached to the RecyclerView.

Parameters
view View: The View which is attached to the RecyclerView

onChildViewDetachedFromWindow

added in version 22.2.0
void onChildViewDetachedFromWindow (View view)

Called when a view is detached from RecyclerView.

Parameters
view View: The View which is being detached from the RecyclerView

onDraw

added in version 22.2.0
void onDraw (Canvas c, 
                RecyclerView parent, 
                RecyclerView.State state)

Draw any appropriate decorations into the Canvas supplied to the RecyclerView. Any content drawn by this method will be drawn before the item views are drawn, and will thus appear underneath the views.

Parameters
c Canvas: Canvas to draw into
parent RecyclerView: RecyclerView this ItemDecoration is drawing into
state RecyclerView.State: The current state of RecyclerView

onDrawOver

added in version 22.2.0
void onDrawOver (Canvas c, 
                RecyclerView parent, 
                RecyclerView.State state)

Draw any appropriate decorations into the Canvas supplied to the RecyclerView. Any content drawn by this method will be drawn after the item views are drawn and will thus appear over the views.

Parameters
c Canvas: Canvas to draw into
parent RecyclerView: RecyclerView this ItemDecoration is drawing into
state RecyclerView.State: The current state of RecyclerView.

startDrag

added in version 22.2.0
void startDrag (RecyclerView.ViewHolder viewHolder)

Starts dragging the provided ViewHolder. By default, ItemTouchHelper starts a drag when a View is long pressed. You can disable that behavior by overriding isLongPressDragEnabled().

For this method to work:

  • The provided ViewHolder must be a child of the RecyclerView to which this ItemTouchHelper is attached.
  • ItemTouchHelper.Callback must have dragging enabled.
  • There must be a previous touch event that was reported to the ItemTouchHelper through RecyclerView's ItemTouchListener mechanism. As long as no other ItemTouchListener grabs previous events, this should work as expected.
For example, if you would like to let your user to be able to drag an Item by touching one of its descendants, you may implement it as follows:
     viewHolder.dragButton.setOnTouchListener(new View.OnTouchListener() {
         public boolean onTouch(View v, MotionEvent event) {
             if (MotionEvent.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
                 mItemTouchHelper.startDrag(viewHolder);
             }
             return false;
         }
     });
 

Parameters
viewHolder RecyclerView.ViewHolder: The ViewHolder to start dragging. It must be a direct child of RecyclerView.

See also:

startSwipe

added in version 22.2.0
void startSwipe (RecyclerView.ViewHolder viewHolder)

Starts swiping the provided ViewHolder. By default, ItemTouchHelper starts swiping a View when user swipes their finger (or mouse pointer) over the View. You can disable this behavior by overriding ItemTouchHelper.Callback

For this method to work:

  • The provided ViewHolder must be a child of the RecyclerView to which this ItemTouchHelper is attached.
  • ItemTouchHelper.Callback must have swiping enabled.
  • There must be a previous touch event that was reported to the ItemTouchHelper through RecyclerView's ItemTouchListener mechanism. As long as no other ItemTouchListener grabs previous events, this should work as expected.
For example, if you would like to let your user to be able to swipe an Item by touching one of its descendants, you may implement it as follows:
     viewHolder.dragButton.setOnTouchListener(new View.OnTouchListener() {
         public boolean onTouch(View v, MotionEvent event) {
             if (MotionEvent.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
                 mItemTouchHelper.startSwipe(viewHolder);
             }
             return false;
         }
     });
 

Parameters
viewHolder RecyclerView.ViewHolder: The ViewHolder to start swiping. It must be a direct child of RecyclerView.
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