android - how to catch Drop action of ItemTouchHelper which is used with RecyclerView
Solution 1
While dragging and dropping an item, the onMove() can be called more than once, but the clearView() will be called once. So you can use this to indicate the drag was over(drop was happened). And use two variables dragFrom and dragTo to trace the really position in a completed "drag & drop".
private ItemTouchHelper.Callback dragCallback = new ItemTouchHelper.Callback() {
int dragFrom = -1;
int dragTo = -1;
@Override
public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
return makeMovementFlags(ItemTouchHelper.UP|ItemTouchHelper.DOWN|ItemTouchHelper.LEFT|ItemTouchHelper.RIGHT,
0);
}
@Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
int fromPosition = viewHolder.getAdapterPosition();
int toPosition = target.getAdapterPosition();
if(dragFrom == -1) {
dragFrom = fromPosition;
}
dragTo = toPosition;
adapter.onItemMove(fromPosition, toPosition);
return true;
}
private void reallyMoved(int from, int to) {
// I guessed this was what you want...
}
@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
}
@Override
public boolean isLongPressDragEnabled() {
return true;
}
@Override
public boolean isItemViewSwipeEnabled() {
return false;
}
@Override
public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
super.clearView(recyclerView, viewHolder);
if(dragFrom != -1 && dragTo != -1 && dragFrom != dragTo) {
reallyMoved(dragFrom, dragTo);
}
dragFrom = dragTo = -1;
}
};
adapter.onItemMove(fromPosition, toPosition) was like below:
public void onItemMove(int fromPosition, int toPosition) {
list.add(toPosition, list.remove(fromPosition));
notifyItemMoved(fromPosition, toPosition);
}
Solution 2
The onSelectedChanged(RecyclerView.ViewHolder, int)
callback provides information about the current actionState:
- ACTION_STATE_IDLE
:
- ACTION_STATE_DRAG
- ACTION_STATE_SWIPE
So you could keep track whether the order changed, and when the state changes to ACTION_STATE_IDLE
, you can do what you need to do!
Example:
private final class MyCallback extends ItemTouchHelper.Callback {
private boolean mOrderChanged;
@Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
// Check if positions of viewHolders correspond to underlying model, and if not, flip the items in the model and set the mOrderChanged flag
mOrderChanged = true;
}
@Override
public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
super.onSelectedChanged(viewHolder, actionState);
if (actionState == ItemTouchHelper.ACTION_STATE_IDLE && mOrderChanged) {
doSomething();
mOrderChanged = false;
}
}
Solution 3
I did some tests and onSelectedChanged(RecyclerView.ViewHolder?, Int)
seemed most reliable for me to detect end of the gesture (drop). The method is called whenever an item is being dragged and passed action state of ACTION_STATE_DRAG
. When the drag is over, it is called with action state of ACTION_STATE_IDLE
.
See my solution below. The onItemDrag(Int, Int)
callback is used for reordering items in an adapter as the item is being dragged. On the other hand the onItemDragged(Int, Int)
callback is intended for updating positions in a database at the end of the gesture.
class ItemGestureHelper(private val listener: OnItemGestureListener) : ItemTouchHelper.Callback() {
interface OnItemGestureListener {
fun onItemDrag(fromPosition: Int, toPosition: Int): Boolean
fun onItemDragged(fromPosition: Int, toPosition: Int)
fun onItemSwiped(position: Int)
}
private var dragFromPosition = -1
private var dragToPosition = -1
// Other methods omitted...
override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
// Item is being dragged, keep the current target position
dragToPosition = target.adapterPosition
return listener.onItemDrag(viewHolder.adapterPosition, target.adapterPosition)
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
listener.onItemSwiped(viewHolder.adapterPosition)
}
override fun onSelectedChanged(viewHolder: RecyclerView.ViewHolder?, actionState: Int) {
super.onSelectedChanged(viewHolder, actionState)
when (actionState) {
ItemTouchHelper.ACTION_STATE_DRAG -> {
viewHolder?.also { dragFromPosition = it.adapterPosition }
}
ItemTouchHelper.ACTION_STATE_IDLE -> {
if (dragFromPosition != -1 && dragToPosition != -1 && dragFromPosition != dragToPosition) {
// Item successfully dragged
listener.onItemDragged(dragFromPosition, dragToPosition)
// Reset drag positions
dragFromPosition = -1
dragToPosition = -1
}
}
}
}
}
Solution 4
You must implement OnMove listener in you adapter:
Collections.swap(youCoolList, fromPosition, toPosition);
notifyItemMoved(fromPosition, toPosition);
like this man doing https://medium.com/@ipaulpro/drag-and-swipe-with-recyclerview-b9456d2b1aaf#.blviq6jxp
special grid example https://medium.com/@ipaulpro/drag-and-swipe-with-recyclerview-6a6f0c422efd#.xb74uu7ke
Related videos on Youtube
Comments
-
okarakose almost 4 years
I have a problem with ItemTouchHelper of RecyclerView.
I am making a game. The game board is actually a RecyclerView. RecyclerView has GridLayoutManager with some span count. I want to implement drag & drop recyclerview's items. Any item can dragging over all directions (up, down, left, right).
private void initializeLayout() { recyclerView.setHasFixedSize(true); recyclerView.setLayoutFrozen(true); recyclerView.setNestedScrollingEnabled(false); // set layout manager GridLayoutManager layoutManager = new GridLayoutManager(getContext(), BOARD_SIZE, LinearLayoutManager.VERTICAL, true); recyclerView.setLayoutManager(layoutManager); // Extend the Callback class ItemTouchHelper.Callback itemTouchCallback = new ItemTouchHelper.Callback() { public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) { Log.w(TAG, "onMove"); return false; } @Override public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) { // Application does not include swipe feature. } @Override public void onMoved(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, int fromPos, RecyclerView.ViewHolder target, int toPos, int x, int y) { Log.d(TAG, "onMoved"); // this is calling every time, but I need only when user dropped item, not after every onMove function. } @Override public boolean isItemViewSwipeEnabled() { return false; } @Override public boolean isLongPressDragEnabled() { return true; } @Override public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) { int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.START | ItemTouchHelper.END; int swipeFlags = 0; return makeMovementFlags(dragFlags, swipeFlags); } }; ItemTouchHelper touchHelper = new ItemTouchHelper(itemTouchCallback); touchHelper.attachToRecyclerView(recyclerView); }
SO, why ItemTouchHelper's onMoved function works when I still dragging item on the RecyclerView ? How can I achieve this ?
-
Ucdemir about 8 yearsI was looking this :=)
-
andre719mv over 7 yearsWorks as expected
-
seekingStillness over 7 yearsI've been trying to figure out how to know the drop has completed. Your explanation of the clearView() is perfect. Thanks for showing the implementation as well.
-
Matan Dahan about 7 yearsThis was also my intuitive answer, but apparently it does not work as expected...
-
andygeers over 6 yearsI used a method like this successfully by tracking the previous state each time
onSelectedChanged
was called - if it USED to beACTION_STATE_DRAG
and is nowACTION_STATE_IDLE
thendoSomething()
-
Yusuf Çağlar over 6 yearsThis is way to go!
-
Riddhi Shankar almost 6 yearsWorked as Expected, Thank you so much :)
-
Carnal over 5 yearsThank you, very nice solution!
-
brucemax about 5 yearsI use recycle view in motion layout and clearView calls every time when I cross next item :( It start from removeAndRecycleScrapInt method in recycleview because getScrapCount() != 0 Upd: This behavior starts when I move from constraint-layout-alpha3 to beta1
-
Adrian Grygutis almost 5 yearsWorks perfect for me!
-
AlexS over 4 yearsThis called when view is drag, not dropped. This is not work
-
Vivek about 4 yearsThis will be perfect solution for those who just wanted to implement drag and drop action . As clearView() will be called in both in Drag and Swipe action and then differentiating between the action won't be possible
-
Dan almost 4 years@andre719mv in which class i have write this above code, i mean in activity class, adapter or in class class DragItemTouchHelper extends ItemTouchHelper.Callback class ??
-
Dan almost 4 yearsIn which class i have write this above code, i mean in activity class, adapter or in class class DragItemTouchHelper extends ItemTouchHelper.Callback class ??
-
Dan almost 4 yearsPlease help me on same question stackoverflow.com/questions/62653282
-
Egist Li over 3 yearsThis is NOT the right way to do it since
clearView
can be called when a viewholder is somehow scrapped by recyclerview! This leads to incorrect timeing for calling your subsequence logics which may lead to crashes. UseonSelectedChanged
is the right way to go. InonSelectedChanged
you can checkviewHolder == null
and IDLE state which means a drop is finished (hence selected is set tonull
) -
Dr.jacky over 3 yearsFor me,
viewHolder
is always null!