强制类型装换错误的问题！有大神来看看吗？

Question

  @Override
                                    public void onToggle(boolean isExpand, RecyclerView.ViewHolder holder) {

                                     //int position=holder.getAdapterPosition();
                                      DirectoryNodeBinder.ViewHolder dirViewHolder = (DirectoryNodeBinder.ViewHolder) holder;
                                        final ImageView ivArrow = dirViewHolder.getIvArrow();
                                        int rotateDegree = isExpand ? 90 : -90;
                                        ivArrow.animate().rotationBy(rotateDegree)
                                                .start();
                                    }

这句话为什么会报强制类型装换错误。下面是这个 DirectoryNodeBinder.ViewHolder类的写法。有大神给小弟解解疑惑吗？？？？

public class DirectoryNodeBinder extends TreeViewBinder<DirectoryNodeBinder.ViewHolder> {
    @Override
    public ViewHolder provideViewHolder(View itemView) {
        return new ViewHolder(itemView);
    }

    @Override
    public void bindView(ViewHolder holder, int position, TreeNode node) {
        holder.ivArrow.setRotation(0);
        holder.ivArrow.setImageResource(R.drawable.ic_keyboard_arrow_right_black_18dp);
        int rotateDegree = node.isExpand() ? 90 : 0;
        holder.ivArrow.setRotation(rotateDegree);
        Dir dirNode = (Dir) node.getContent();
        holder.tvName.setText(dirNode.dirName);
        if (node.isLeaf())
            holder.ivArrow.setVisibility(View.INVISIBLE);
        else holder.ivArrow.setVisibility(View.VISIBLE);
    }

    @Override
    public int getLayoutId() {
        return R.layout.item_dir;
    }

    public static class ViewHolder extends TreeViewBinder.ViewHolder {
        private ImageView ivArrow;
        private TextView tvName;

        public ViewHolder(View rootView) {
            super(rootView);
            this.ivArrow = (ImageView) rootView.findViewById(R.id.iv_arrow);
            this.tvName = (TextView) rootView.findViewById(R.id.tv_name);
        }

        public ImageView getIvArrow() {
            return ivArrow;
        }

        public TextView getTvName() {
            return tvName;
        }
    }

Answer 1

https://blog.csdn.net/guo_jia_liang/article/details/53213008