关于树形图前面箭头无法显示的问题有大神来看看吗？

Question

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);//箭头图标
            this.tvName = (TextView) rootView.findViewById(R.id.tv_name);
        }

        public ImageView getIvArrow() {
            return ivArrow;
        }

        public TextView getTvName() {
            return tvName;
        }
    }
}

这个是DirectoryNodeBinder类，
然后我在树形图里面想加上这个图标我这样写：

 private void initNode() {
        tempList = AppConst.getmSysProjectNavList();
        ArrayList<SysProjectNav> roots = new ArrayList();
        for (int i = 0; i < tempList.size(); i++) {
            if (tempList.get(i).getSysProjectNave_Parent_ID() != null) {
                if (tempList.get(i).getSysProjectNave_Parent_ID().equals(sysProjectNav.getSysProjectNave_ID())) {
                    roots.add(tempList.get(i));
                }
            }
        }
        getTreeData(roots, null);

        LinearLayoutManager layoutManager = new LinearLayoutManager(ManagementActivity.this);
        rv.setLayoutManager(layoutManager);

        adapter = new TreeViewAdapter(nodes, Arrays.asList(new FileNodeBinder(), new DirectoryNodeBinder()));
        adapter.setOnTreeNodeListener(new TreeViewAdapter.OnTreeNodeListener() {
            @Override
            public boolean onClick(TreeNode node, RecyclerView.ViewHolder holder) {
                if (!node.isLeaf()) {
                    onToggle(!node.isExpand(), holder);
                } else {
                    if (node.isRoot()) {//片断树中节点没有内容时使用
                        ToastUtils.showShort("暂无内容");
                    } else {
                        Object obContent = node.getContent();
                        Object obParnet = node.getParent().getContent();
                        // String fileName = ReflexObjectUtil.getValueByKey(obContent, "dirName").toString();
                        String Id = ReflexObjectUtil.getValueByKey(obContent, "ID").toString();
                        String parentName = ReflexObjectUtil.getValueByKey(obParnet, "dirName").toString();

                        //通过点击的文件名找出相应的对象
                        SysProjectNav sysProjectNav = null;
                        for (int i = 0; i < tempList.size(); i++) {
                            if (tempList.get(i).getID().equals(Id)) {
                                sysProjectNav = tempList.get(i);
                                break;
                            }
                        }
                    }
                }
                return false;
            }
            @Override
            public void onToggle(boolean isExpand, RecyclerView.ViewHolder holder) {
                DirectoryNodeBinder.ViewHolder dirViewHolder = (DirectoryNodeBinder.ViewHolder) holder;
                final ImageView ivArrow = dirViewHolder.getIvArrow();
                int rotateDegree = isExpand ? 90 : -90;
                ivArrow.animate().rotationBy(rotateDegree)
                        .start();
            }
        });
        rv.setAdapter(adapter);
        swipeRefresh.setRefreshing(false);
        swipeRefresh.setEnabled(false);
    }

可是会报强制类型错误有人知道这是什么问题吗？或者怎么才能给树形图加上箭头

Answer 1

强制转换用 (FileNodeBinder.ViewHolder)holder;