Animate Any Listview/Gridview changes.

//MIT license


    handleViewDatasetChange();
    swapElements(mBackingList, mMobileAdapterPosition, mMobileAdapterPosition + positionChange);



    private static class IdLocator {
        public int left;
        public int top;
        public boolean visible;

        public IdLocator(int left, int top, boolean visible) {
            this.left = left;
            this.top = top;
            this.visible = visible;
        }
    }

    public void handleViewDatasetChange() {
        //THIS MUST BE CALLED PRIOR TO THE UNDERLYING CHANGES IN THE ADAPTER.
        //It saves the state, and calls the notify, and plugs in the predraw listener animations.

        //Save the adapter state.
        final HashMap<Long,IdLocator> locations = new HashMap<>(getChildCount());
        int firstVisiblePosition = getFirstVisiblePosition();
        Adapter adapter = getAdapter();
        for (int i = 0, s = getChildCount(); i < s; i++) {
            View v = getChildAt(i);
            int position = firstVisiblePosition + i;
            long id = adapter.getItemId(position);
            locations.put(id, new IdLocator(v.getLeft(), v.getTop(), v.getVisibility() == View.VISIBLE));
            v.setVisibility(VISIBLE);
        }

        ((BaseAdapter) getAdapter()).notifyDataSetChanged();


        final ViewTreeObserver observer = getViewTreeObserver();
        observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
            public boolean onPreDraw() {
                observer.removeOnPreDrawListener(this);

                int firstVisiblePosition = getFirstVisiblePosition();
                Adapter adapter = getAdapter();

                //Animate the changes from the saved states.
                for (int i = 0, s = getChildCount(); i < s; i++) {
                    int position = firstVisiblePosition + i;
                    long id = adapter.getItemId(position);
                    IdLocator idLocator = locations.get(id);
                    if (idLocator == null) continue;

                    View v = getChildAt(i);

                    if (!idLocator.visible) v.setVisibility(INVISIBLE);
                    else v.setVisibility(VISIBLE);

                    int changeLeft = idLocator.left - v.getLeft();
                    if (changeLeft != 0) {
                        v.setTranslationX(changeLeft);
                        Animator animatorX = ObjectAnimator.ofFloat(v, View.TRANSLATION_X, 0);
                        animatorX.setDuration(MOVE_DURATION);
                        animatorX.start();
                    }

                    int changeTop = idLocator.top - v.getTop();
                    if (changeTop != 0) {
                        v.setTranslationY(changeTop);
                        Animator animatorY = ObjectAnimator.ofFloat(v, View.TRANSLATION_Y, 0);
                        animatorY.setDuration(MOVE_DURATION);
                        animatorY.start();
                    }
                }
                return true;
            }
        });
    }