如何使用DiffUtil获取插入项的位置？

public class MyDiffCallback extends DiffUtil.Callback {
    private List<Item> oldList;
    private List<Item> newList;

    public MyDiffCallback(List<Item> oldList, List<Item> newList) {
        this.oldList = oldList;
        this.newList = newList;
    }

    @Override
    public int getOldListSize() {
        return oldList.size();
    }

    @Override
    public int getNewListSize() {
        return newList.size();
    }

    @Override
    public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
        Item oldItem = oldList.get(oldItemPosition);
        Item newItem = newList.get(newItemPosition);
        return oldItem.getId() == newItem.getId();
    }

    @Override
    public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
        Item oldItem = oldList.get(oldItemPosition);
        Item newItem = newList.get(newItemPosition);
        return oldItem.equals(newItem);
    }
}

// 在需要更新数据集的地方
List<Item> oldList = ...; // 旧数据集
List<Item> newList = ...; // 新数据集

MyDiffCallback diffCallback = new MyDiffCallback(oldList, newList);
DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(diffCallback);

// 将差异应用到RecyclerView的适配器中
diffResult.dispatchUpdatesTo(adapter);

// 获取插入项的位置
int insertedPosition = diffCallback.getNewListSize() - 1;