public abstract class BaseTreeRVAdapter<T extends RecyclerView.ViewHolder, M extends Tree> extends BaseRVAdapterV2<T, M> {

    @Override
    public void onBindViewHolder(T holder, final int position) {
        try {
            getLevel(position, mDatas, new PosBean());
        } catch (StopMsgException ex) {
            int type = Integer.parseInt(ex.getMessage());
            M tree = ex.getTree();
            onBindViewHolder(type, tree, holder);
        }
    }


    @Override
    public int getItemViewType(int position) {
        try {
            getLevel(position, mDatas, new PosBean());
        } catch (StopMsgException ex) {
            return Integer.parseInt(ex.getMessage());
        }
        return 0;
    }

    @Override
    public int getItemCount() {
        return getTotal(mDatas);
    }

    protected abstract void onBindViewHolder(int type, M tree, T holder);

    public List<M> getDatas() {
        return mDatas;
    }

    public void setDatas(List<M> info) {
        if (info != null) {
            mDatas = info;
        } else {
            mDatas.clear();
        }
        notifyDataSetChanged();
    }
}

public class TreeListAdapter extends BaseTreeRVAdapter<RecyclerView.ViewHolder, T extends Tree> {

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view;
        RecyclerView.ViewHolder vh;
        switch (viewType) {
            case 0:
                ......    
                break;
            case 1:
                ......
                break;
            case 2:
                ......
                break;
            case 3:
            case 4:
            ......
        }
        return vh;
    }


    @Override
    protected void onBindViewHolder(int type, final DiscountItem itemCategoryListBean, RecyclerView.ViewHolder holder) {
        switch (type) {
            case 0:
                ......
                break;
            case 1:
                ......
                break;
            case 2:
                ......
                break;
            case 3:
            case 4:
            ......
        }
    }
}

    int getLevel();//每个item的层级，比如一级就是0，二级就返回1，这里的0和1可以自己定义，后面就是根据这个来选择哪种样式的item

    List<T> getChilds();//返回的子列表，比如当前类是一级的话，那么这个方法返回的是二级的列表数据

    boolean isExpand();//是否展开，true展开，false不展开，一般就是点击下去修改这个值刷新adapter，就能达到展开还是折叠的目的了

step 1.
Add it in your root build.gradle at the end of repositories:

	allprojects {
		repositories {
			...
			maven { url 'https://jitpack.io' }
		}
	}
Step 2. Add the dependency

	dependencies {
	        implementation 'com.github.WelliJohn:MultiLevelRecyclerView:0.0.1'
	}