由于recyclerview拖放的变化，如何更新ArrayList中的所有项目

Question

我RecyclerView的布局是GridLayout3列。我正在使用ItemTouchHelper拖放GridLayout的RecyclerView。在我的适配器中，有一种方法onItemMove()可以通知我我已移动的物品。它只交换那些ArrayList我拖放过的项目。但是由于拖放，其他元素也会发生变化。我也想更新他们在中的职位ArrayList。

这是我的Recyclerview的适配器：

public class GridAdapter extends RecyclerView.Adapter<GridAdapter.MyViewHolder> implements com.sagar.quizdemo.helper.ItemTouchHelperAdapter {
    String[] str = {"Level 1", "Level 2", "Level 3", "Level 4", "Level 5", "Level 6", "Level 7", "Level 8", "Level 9"};
    List<String> itemList, actualList;
    LayoutInflater inflater;
    Context context;
    private final OnStartDragListener mDragStartListener;

    public GridAdapter(Context context, OnStartDragListener dragStartListener) {
        this.context = context;
        mDragStartListener = dragStartListener;
        inflater = LayoutInflater.from(context);
        itemList = new ArrayList<>();
        actualList = new ArrayList<>(Arrays.asList(str));
    }

    public void getItemList(List<String> nameList) {
        int currentSize = itemList.size();
        itemList.clear();
        itemList.addAll(nameList);
        notifyItemRangeRemoved(0, currentSize);
        notifyItemRangeInserted(0, nameList.size());
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = inflater.inflate(R.layout.custom_level_row, parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final MyViewHolder holder, int position) {
        holder.textView.setText(itemList.get(position));
        // Start a drag whenever the handle view it touched
        holder.cardView.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (MotionEventCompat.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
                    mDragStartListener.onStartDrag(holder);
                }
                return false;
            }
        });
    }

    @Override
    public int getItemCount() {
        return itemList.size();
    }

    @Override
    public boolean onItemMove(int fromPosition, int toPosition) {
        Collections.swap(itemList, fromPosition, toPosition);
        notifyItemMoved(fromPosition, toPosition);
        notifyItemChanged(fromPosition);
        notifyItemChanged(toPosition);
        return true;
    }

    @Override
    public void onItemDismiss(int position) {
        itemList.remove(position);
        notifyItemRemoved(position);
    }

    public class MyViewHolder extends RecyclerView.ViewHolder implements ItemTouchHelperViewHolder {

        CardView cardView;
        TextView textView;

        public MyViewHolder(View itemView) {
            super(itemView);
            cardView = (CardView) itemView.findViewById(R.id.gameCard);
            textView = (TextView) itemView.findViewById(R.id.gameText);
        }

        @Override
        public void onItemSelected() {
            itemView.setBackgroundColor(Color.LTGRAY);
        }

        @Override
        public void onItemClear() {
            itemView.setBackgroundColor(Color.WHITE);
        }
    }
}

如果最初的列表是：

{"Level 1", "Level 2", "Level 3", "Level 4", "Level 5", "Level 6", "Level 7", "Level 8", "Level 9"}

之后，我在RecyclerView中交换了第二和第四定位的元素。更新后的列表应如下所示（我想要）：

{"Level 1", "Level 5", "Level 2", "Level 3", "Level 4", "Level 6", "Level 7", "Level 8", "Level 9"}

但是我得到这个更新的列表：

{"Level 1", "Level 5", "Level 3", "Level 4", "Level 2", "Level 6", "Level 7", "Level 8", "Level 9"}

Answer 1

我相信您的问题是您使用Collections.swap(itemList, fromPosition, toPosition);，它会在指定位置交换对象。所以输出是正确的。不过，您需要什么：

String item = itemList.remove(fromPostion);
itemList.insert(item, toPosition);