Android RecyclerView自由拖动item的实现代码

private static class MyItemTouchHelperCallback extends ItemTouchHelper.Callback {
        private final ItemAdapter itemAdapter;
        public MyItemTouchHelperCallback(ItemAdapter itemAdapter) {
            this.itemAdapter= itemAdapter;
        }
        @Override
        public int getMovementFlags(@NonNull RecyclerView recyclerView,
                                    @NonNull RecyclerView.ViewHolder viewHolder) {
            int layoutPosition = viewHolder.getLayoutPosition();
            ItemInfo item = ItemAdapter.getItem(layoutPosition);
            if (!item.isMovable()) {
                //不可拖动
                return makeMovementFlags(0, 0);
            }
            //这里表示可以拖动的方向，比如如果不给往上方拖动则去掉ItemTouchHelper.UP
            final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN
                    | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
            return makeFlag(ItemTouchHelper.ACTION_STATE_DRAG, dragFlags);
        }
        @Override
        public boolean onMove(@NonNull RecyclerView recyclerView,
                              @NonNull RecyclerView.ViewHolder viewHolderSource,
                              @NonNull RecyclerView.ViewHolder viewHolderTarget) {
            int layoutPosition = viewHolderTarget.getLayoutPosition();
            ItemInfo item = itemAdapter.getItem(layoutPosition);
            if (!item.isMovable()) {
                //不可拖动到这里
                return false;
            }
            itemAdapter.onMove(viewHolderSource.getAdapterPosition(),
                    viewHolderTarget.getAdapterPosition());
            return true;
        }
        @Override
        public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int i) {
        }
    }

    public ItemInfo getItem(int position) {
        if (position >= 0 && position < mList.size()) {
            return mList.get(position);
        }
        return null;
    }
    public void onMove(int sourcePosition, int targetPosition) {
        ItemInfo item = mList.get(sourcePosition);
        mList.remove(sourcePosition);
        mList.add(targetPosition, item);
        notifyItemMoved(sourcePosition, targetPosition);
    }

    ItemTouchHelper itemTouchHelper = new ItemTouchHelper(
                new MyItemTouchHelperCallback(adapter));
    itemTouchHelper.attachToRecyclerView(recyclerView);

    holder.view.setOnClickListener(v -> {
        int currentPosition = holder.getAdapterPosition();
        ItemInfo info = getItem(currentPosition);
        if (listener != null) {
            listener.onItemClick(currentPosition, info);
        }
    });