如何在RecyclerView中保存新项目？

Question

我正在尝试制作一个RecyclerView，可以拖动它以交换和滑动以使用3种不同的视图进行删除。然后switch-case对它们进行分类。交换和拖动部分很好。

但是，我想实现add功能，当我分别单击三个不同的按钮并且View本身添加得很好时，但是，当我向上或向下滚动时，或当我添加了新按钮。

此代码已简化为看起来更简洁，但是我有三种不同的视图，并且将其分类为哪种视图。

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> implements OnItemMoveListener {
    private final static String TAG = MyAdapter.class.getSimpleName();
    ArrayList<MyItem> items;
    private static final int VIEW_MESSAGE = 0;

    /**
     * A listener for Move & Swipe. It detects dragging from the user.
     */

    public MyAdapter(ArrayList<MyItem> items) {
        this.items = items;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = null;
        switch (viewType) {
            default: {
                v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_edit_message, parent, false);
                break;
            }
        }
        return new MyViewHolder(v);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        switch (holder.getItemViewType()) {
            case VIEW_MESSAGE: {
                MyItem item = items.get(position);
                holder.messageTV.setText(item.getMessage());                
                break;
            }
        }
    }

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

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

    @Override
    public void onItemDissmiss(int position) {
        items.remove(position);
        notifyItemRemoved(position);
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {
        TextView messageTV;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            messageTV = itemView.findViewById(R.id.message);
        }
    }

    @Override
    public int getItemViewType(int position) {
        Log.d(TAG, "getItemViewType() = position: " + position);

        switch (items.get(position).getType()) {
            default:
                return VIEW_MESSAGE;
        }
    }

    public void setItems(ArrayList<MyItem> items) {
        Log.d(TAG, items.size() + "");
        this.items = items;
        notifyDataSetChanged();
    }

    public ArrayList<MyItem> getItems() {
        return items;
    }
}

这是单击“按钮”后来自“活动”代码的一部分，它可以运行。

    public void addNewMassageView(int type) {
        Items = myAdapter.getMessageItems();
        Items.add(new MessageItem(type));;
        Log.d(TAG, Items.size() + "");
        myAdapter.setItems(items);
        recycleView.scrollTo(0, recycleView.getBottom());
    }

我试图getChildViews并提取像这样的值：

    public ArrayList<MyItem> getItemsFromView() {
        ArrayList<MyItem> viewItems = new ArrayList<>();

        recycleView.postDelayed(() -> {
            for (int i = 0; i < items.size(); i++) {
                Log.d(TAG, "i: " + i);
                final int idx = i;
                RecyclerView.ViewHolder holder = recycleView.findViewHolderForAdapterPosition(idx);
                switch (items.get(idx).getType()) {
                    case MESSAGE: {
                        EditText messageET = holder.itemView.findViewById(R.id.message);
                        String message = messageET.getText().toString();

                        viewItems.add(new MyItem(MESSAGE, message));
                        break;
                    }
                }
            }
        }, 50);

        return viewItems;
    }

但是我得到了空引用错误...

出什么问题了？