RecyclerView.getChild(index) shows null when list is scrolled (index gets messed up)

Question

I've been using SwipeableRecyclerView for my android application for enabling swipes for my recyclerView. RecyclerView contains a list of cardViews.

I was trying to implement undo functionality for cards which will get deleted when swipe to left (first swipe shows undo, next swipe triggers delete)

I am trying the following code (partially working I guess)

SwipeableRecyclerViewTouchListener srvTouchListner = new SwipeableRecyclerViewTouchListener(rvTimerList,
            new SwipeableRecyclerViewTouchListener.SwipeListener(){

                @Override
                public boolean canSwipe(int i) {
                    return true;
                }

                @Override
                public void onDismissedBySwipeLeft(RecyclerView recyclerView, int[] ints) {
                    for(int position : ints){
                        View view = recyclerView.getChildAt(position);
                            if (view.getTag(R.string.card_undo) == null) {
                                if(viewStack == null) {
                                    saveToViewStack(position, view);
                                    final ViewGroup viewGroup = (ViewGroup) view.findViewById(R.id.time_card2);
                                    view.setTag(R.string.card_undo, "true");
                                    viewGroup.addView(view.inflate(TimerSummary.this, R.layout.timeslot_card_undo, null));
                                }
                            } else {
                                Log.d(TAG, "Removing Item");
                                deleteTimeSlot(timerInstanceList.get(position));
                                Toast.makeText(TimerSummary.this, "Deleted!", Toast.LENGTH_SHORT).show();
                                timerInstanceList.remove(position);
                                finalSummaryAdapter.notifyItemRemoved(position);
                            }

                    }
                    finalSummaryAdapter.notifyDataSetChanged();
                }
                @Override
                public void onDismissedBySwipeRight(RecyclerView recyclerView, int[] ints) {
                    for (int position:ints){
                        View view = recyclerView.getChildAt(position);
                        if(view.getTag(R.string.card_undo) != null && view.getTag(R.string.card_undo).equals("true")){
                            viewStack = null;
                            recyclerView.setAdapter(finalSummaryAdapter);
                        }
                    }

                }
            });

when Items are more (needs scrolling)

View view = recyclerView.getChildAt(position);

returns a null reference which causes an app crash.

I doubt that I am using the wrong method for taking view. I should be using something related with viewholder, I am actually kind of confused about how to get the view which you want from viewholder.

If anybody can share anything that helps,, that'll be great! I ll be happy to provide any more infos if somebody wants it,

Answer 1

You should use findViewHolderForAdapterPosition. https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html#findViewHolderForAdapterPosition(int)

Keep in mind that it will return null if the position is not laid out (e.g. out of bounds or removed).