RecyclerView的滑動刪除和排序

http://blog.csdn.net/javacainiao931121/article/details/51704672
根據上述網址的博客內容，在MainActivity中添加代碼實現RecyclerView滑動刪除和排序功能。

ItemTouchHelper.Callback callback = new ItemTouchHelper.SimpleCallback(ItemTouchHelper.UP | ItemTouchHelper.DOWN, ItemTouchHelper.RIGHT | ItemTouchHelper.LEFT) {
            @Override
            public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
                //得到拖動ViewHolder的position
                int fromPosition = viewHolder.getAdapterPosition();
                //得到目標ViewHolder
                int toPosition = target.getAdapterPosition();
                if (fromPosition < toPosition) {
                //分別把中間所有的item的位置重新交換
                    for (int i = fromPosition; i < toPosition; ++i) {
                        Collections.swap(list, i, i + 1);
                    }
                } else {
                    for (int i = fromPosition; i > toPosition; i--) {
                        Collections.swap(list, i, i - 1);
                    }
                }
                homeAdapter.notifyItemMoved(fromPosition, toPosition);
                //返回true表示執行拖動
                return true;
            }

            @Override
            public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
                int position = viewHolder.getAdapterPosition();
                list.remove(position);
                homeAdapter.notifyItemRemoved(position);
            }

            @Override
            public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
                super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
                if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
                    //左右滑動時改變Item的透明度
                    final float alpha = 1 - Math.abs(dX) / (float) viewHolder.itemView.getWidth();
                    viewHolder.itemView.setAlpha(alpha);
                    viewHolder.itemView.setTranslationX(dX);
                }
            }

            @Override
            public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
                super.onSelectedChanged(viewHolder, actionState);
                //當選中Item時候會調用該方法，重寫此方法可以實現選中時候的一些動畫邏輯
                Log.v("wx", "onSelectedChanged");
            }

            @Override
            public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
                super.clearView(recyclerView, viewHolder);
                //當動畫已經結束的時候調用該方法，重寫此方法可以實現恢復Item的初始狀態
                Log.v("wx", "clearView");
            }
        };
        ItemTouchHelper itemTouchHelper = new ItemTouchHelper(callback);
        itemTouchHelper.attachToRecyclerView(recyclerView);