Bdtjtk

I am implementing onDragDrop method in the adapter class.

 public boolean onDragDrop(int fromPosition, int toPosition) {

    Collections.swap(list, fromPosition, toPosition);

    notifyItemMoved(fromPosition, toPosition);

    if (fromPosition < toPosition) {

        notifyItemRangeChanged(fromPosition, list.size());

    } else {

        notifyItemRangeChanged(toPosition, list.size());

    }

    return true;

}

The problem I am facing is when onDragDrop method is implemented, the animation is not good; there's a trace of elements before being replaced. I understand that for drag and drop, just notifyItemMoved method is enough, and with that, the animation is perfect. The reason I am implementing notifyItemRangeChanged is that after drag and drop, I want the data to get refreshed.

I went through a lot of StackOverflow posts and tried implementing the suggestions, but nothing worked. Thanks for your help.

Try adding a third argument to your notifyItemRangeChanged() calls. It can be literally any object, but I recommend Boolean.FALSE since it won't take up any extra memory and because "false" and "don't run an animation I don't want" are sort of related concepts.

if (fromPosition < toPosition) {

    notifyItemRangeChanged(fromPosition, list.size(), Boolean.FALSE);

} else {

    notifyItemRangeChanged(toPosition, list.size(), Boolean.FALSE);

}

The reason this should work has to do with what the whole RecyclerView system does when you notify the adapter that items have changed. Part of that process involves the DefaultItemAnimator, which has to decide whether to re-use old ViewHolder instances or not. You want this re-using, but you're not getting it.

When you pass a third argument to notifyItemRangeChanged(), that third argument is passed around the system as a "payload". DefaultItemAnimator is one piece of the system that receives this payload, and it decides whether or not to re-use ViewHolders based on whether or not this payload exists.

@Override

public boolean canReuseUpdatedViewHolder(@NonNull RecyclerView.ViewHolder viewHolder,

        @NonNull List<Object> payloads) {

    return !payloads.isEmpty() || super.canReuseUpdatedViewHolder(viewHolder, payloads);

}

In your current code, there's no payload, so ViewHolders don't get re-used. This causes an animation of the "old" ViewHolder fading out and the "new" ViewHolder fading in, which looks an awful lot like a flicker.

When you add the third argument, suddenly there's a payload. Again, it doesn't matter what the payload is, just that it exists at all. Now your ViewHolder can be re-used, so there's no fade in/out animation.