分类（left。right）

1.model层（ITask）

public interface ITask {
    //得到商品列表
    void getListData(String url, OkCallback callback);
}

Task

public class Task implements ITask{

    @Override
    public void getListData(String url, OkCallback callback) {
        OK.getOk().doGet(url,callback);
    }
}

2：Presenter层（BasePresenter）

public interface BasePresenter  {
    void Destory();
}

IPresenter

public interface IPresenter extends BasePresenter{
    //得到商品列表
    void getList();
}

Presenter

public class MyPresenter extends OkCallback implements IPresenter {
    //注入M层
    Task task;
    //注入V层
    IView view;

    public MyPresenter(MainActivity activity) {
        task=new Task();
        view= (IView) activity;
    }

    @Override
    public void getList() {
        //得到商品列表
        task.getListData("http://39.108.3.12:3000/v1/food/32",this);
    }

    @Override
    public void onUI(String json) {
        //解析
        Gson gson=new Gson();
        ResData resData = gson.fromJson(json, ResData.class);
        //展示
        view.showData(resData.data);

    }

    @Override
    public void onFailed(String json) {

    }
    //销毁，防止内存泄漏
    @Override
    public void Destory() {
        view=null;
    }
}

3：View

public interface IView {
    //展示数据
    void showData(List<SetMeal> meals);
}

4：适配器

\\左边

public class LeftAdapter extends RecyclerView.Adapter<LeftAdapter.LeftHolder>{
    private LeftItemClickListener itemClickListener;
    private List<SetMeal> list;
    public LeftAdapter() {
       this.list=new ArrayList<>();
    }

    public void addData(List<SetMeal> meals) {
        this.list.addAll(meals);
        notifyDataSetChanged();
    }

    class LeftHolder extends RecyclerView.ViewHolder{
        TextView left_text;
        public LeftHolder(View itemView) {
            super(itemView);
            left_text=itemView.findViewById(R.id.left_text);
        }
    }
    @NonNull
    @Override
    public LeftHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
          View view=LayoutInflater.from(parent.getContext()).inflate(R.layout.left_recycler_layout,parent,false);
        return new LeftHolder(view);
    }
    @Override
    public void onBindViewHolder(@NonNull final LeftHolder holder, final int position) {
        final SetMeal meal=list.get(position);
        holder.left_text.setText(meal.name);
        //根据选中状态更新条目背景
        if(meal.isClick){
            holder.itemView.setBackgroundColor(Color.GRAY);
        }else {
            holder.itemView.setBackgroundColor(Color.WHITE);
        }
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               itemClickListener.onItemClick(meal);
               //遍历集合
                for (SetMeal temp: list) {
                    if(temp.id==meal.id){
                        temp.isClick=true;
                    }else{
                        temp.isClick=false;
                    }
                }
               //刷新页面
               notifyDataSetChanged();
            }
        });
    }

    @Override
    public int getItemCount() {
        return list.size();
    }
   //接口
    public interface LeftItemClickListener{
         void onItemClick(SetMeal meal);
   }
    // 向外提供的接口
    public void setItemClickListener(LeftItemClickListener itemClickListener){
        this.itemClickListener=itemClickListener;
    }

}

5：MianActivity

public class MainActivity extends AppCompatActivity implements IView{
     //注入P层
    IPresenter presenter;
    RecyclerView recyclerView1,recyclerView2;
    LeftAdapter adapter1;
    RightAdapter adapter2;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        presenter=new MyPresenter(this);
        presenter.getList();
        initView();
    }
    private void initView() {
        //获取资源id
        recyclerView1=findViewById(R.id.left_recycle);
        recyclerView2=findViewById(R.id.right_recycle);
        //左边
        //布局管理器
        LinearLayoutManager manager=new LinearLayoutManager(this);
        recyclerView1.setLayoutManager(manager);
        //分割线
       recyclerView1.addItemDecoration(new DividerItemDecoration(this, OrientationHelper.VERTICAL));
       adapter1=new LeftAdapter();
       recyclerView1.setAdapter(adapter1);
        //接口回掉
        adapter1.setItemClickListener(new LeftAdapter.LeftItemClickListener() {
            @Override
            public void onItemClick(SetMeal meal) {
                Toast.makeText(MainActivity.this,meal.name,Toast.LENGTH_SHORT).show();
                adapter2.addData(meal.spus);

            }
        });
        //右边
        LinearLayoutManager rightmanager=new LinearLayoutManager(this);
        recyclerView2.setLayoutManager(rightmanager);
        recyclerView2.addItemDecoration(new DividerItemDecoration(this,OrientationHelper.VERTICAL));
        adapter2=new RightAdapter();
        recyclerView2.setAdapter(adapter2);
    }

    //展示数据
    @Override
    public void showData(List<SetMeal> meals) {
        //初始化数据
        //左边
        adapter1.addData(meals);
        //右边
        SetMeal meal=meals.get(0);
        meal.isClick=true;
        adapter2.addData(meal.spus);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
     //调用防止内存泄漏
        presenter.Destory();

    }
}

\\右边

public class RightAdapter extends RecyclerView.Adapter<RightAdapter.RightHolder> {
    List<Spus> list;

    public RightAdapter() {
        this.list=new ArrayList<>();
    }

    public void addData(List<Spus> spus) {
        //清除
        this.list.clear();
        this.list.addAll(spus);
        notifyDataSetChanged();

    }

    @NonNull
    @Override
    public RightAdapter.RightHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.right_recycle_layout,parent,false);
        return new RightHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RightAdapter.RightHolder holder, int position) {
       Spus spus=list.get(position);
       holder.right_text.setText(spus.name);
    }

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


    public class RightHolder extends RecyclerView.ViewHolder{
        TextView right_text;
        public RightHolder(View itemView) {
            super(itemView);
            right_text=itemView.findViewById(R.id.right_text);
        }
    }
}