由于 recyclerview 的拖放移动，如何更新 ArrayList 中的所有项目

Question

我有一个 RecyclerView，其布局是 GridLayout 3 列。我正在使用 ItemTouchHelper 拖放 RecyclerView 的 GridLayout。在我的适配器中有一个方法 onItemMove() 通知我我已经移动的项目。它只交换我拖放的 ArrayList 中的那些项目。但是由于拖放，其他元素也发生了变化。我也想更新他们在 ArrayList.

中的位置

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);
        }
    }
}

如果列表最初是：

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

在我交换 RecyclerView 中的第二个和第四个定位元素之后。更新后的列表应该如下所示（我想要的）：

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

但我收到了这个更新列表：

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

Answer 1

尝试在 onItemMove 方法中调用 notifyDataSetChanged()。

@Override
    public boolean onItemMove(int fromPosition, int toPosition) {
        notifyItemMoved(fromPosition, toPosition);
        notifyItemChanged(fromPosition);
        notifyItemChanged(toPosition);
        notifyDataSetChanged();    
        return true;
    }

Answer 2

我认为您的问题在于您使用 Collections.swap(itemList, fromPosition, toPosition);，它在指定位置交换对象。所以输出是正确的。不过，您需要的是：

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

Answer 3

试试这个。在您的情况下，您首先必须找到要替换的项目的索引 (fromPosition)，然后将 toPosition 添加到该索引。 How to move specific item in array list to the first item

Answer 4

代码 here 为我工作。

 @Override
public boolean onItemMove(int fromPosition, int toPosition) {
    if (fromPosition < toPosition) {
        for (int i = fromPosition; i < toPosition; i++) {
            Collections.swap(listData, i, i + 1);
        }
    } else {
        for (int i = fromPosition; i > toPosition; i--) {
            Collections.swap(listData, i, i - 1);
        }
    }
    notifyItemMoved(fromPosition, toPosition);
    return true;
}

由于 recyclerview 的拖放移动，如何更新 ArrayList 中的所有项目

How to update all the items in ArrayList due to shift in drag and drop of recyclerview

java

android

drag-and-drop

android-recyclerview

itemtouchhelper