概述

左右联动列表是仿照美团外卖点餐时，左右列表可以联动。比如右边列表会有小项对应左边的，滑动时会置顶，滑动到下一个小项时，置顶会切换，并且左边列表的项也相应切换。同理，左边项的点击，右边的列表也会跟着滚动，对应的小项也会置顶。

详细

一、运行效果如下：

shili.gif

二、实现过程：

1、右边列表adapter

public class RightAdapter extends RecyclerView.Adapter {

    private ArrayList<FoodBean> mList;
    private LayoutInflater mLayoutInflater;


    public RightAdapter(LayoutInflater layoutInflater, ArrayList<FoodBean> list) {
        this.mList = list;
        mLayoutInflater = layoutInflater;
    }


    private FoodBean getItem(int position) {
        return mList.get(position);
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new RightViewHolder(
                mLayoutInflater.inflate(R.layout.listitem_right_content, parent, false));
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        FoodBean target = getItem(position);
        if (holder instanceof RightViewHolder) {
            ((RightViewHolder) holder).bindBean(target);
        } else {
            throw new IllegalStateException("Illegal state Exception onBindviewHolder");
        }
    }

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

    private class RightViewHolder extends RecyclerView.ViewHolder {
        private TextView tvFoodTitle;

        private ImageView ivFood;

        RightViewHolder(View itemView) {
            super(itemView);
            tvFoodTitle = (TextView) itemView.findViewById(R.id.tv_food_title);
            ivFood = (ImageView) itemView.findViewById(R.id.iv_food);
        }

        void bindBean(final FoodBean bean) {
            tvFoodTitle.setText(bean.getFoodTitle());
            ivFood.setImageResource(bean.getImageResId());

        }
    }


}  

其中FoodBean.class

public class FoodBean {
    private int imageResId;
    private String foodTitle;
    //这是每小项的标题，用来滑动置顶用
    private String itemTitle;

    public FoodBean(int imageResId, String foodTitle,String itemTitle) {
        this.imageResId = imageResId;
        this.foodTitle = foodTitle;
        this.itemTitle = itemTitle;

    }
    public FoodBean(int imageResId, String foodTitle) {
        this.imageResId = imageResId;
        this.foodTitle = foodTitle;


    }

    public String getItemTitle() {
        return itemTitle;
    }

    public void setItemTitle(String itemTitle) {
        this.itemTitle = itemTitle;
    }

    public int getImageResId() {
        return imageResId;
    }

    public void setImageResId(int imageResId) {
        this.imageResId = imageResId;
    }

    public String getFoodTitle() {
        return foodTitle;
    }

    public void setFoodTitle(String foodTitle) {
        this.foodTitle = foodTitle;
    }
}

2、左边adapter

public class LeftAdapter extends RecyclerView.Adapter<LeftAdapter.LeftViewHolder> {

    private ArrayList<LeftBean> mList;
    private OnItemClickListener onItemClickListener;

    public LeftAdapter( ArrayList<LeftBean> list) {
        this.mList = list;

    }

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }



    private LeftBean getItem(int position) {
        return mList.get(position);
    }

    @Override
    public LeftViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext())
                .inflate(R.layout.listitem_left_content,parent,false);

        return new LeftViewHolder(view);

    }

    @Override
    public void onBindViewHolder(LeftViewHolder holder, int position) {
        LeftBean target = getItem(position);
        holder.tvTitle.setText(target.getTitle());
        if (target.isSelect()){
            holder.itemView.setBackgroundColor(ContextCompat.getColor(holder.itemView.getContext(), R.color.white));
        } else {
            holder.itemView.setBackgroundColor(ContextCompat.getColor(holder.itemView.getContext(), R.color.c_aaa));
        }
        //绑定监听事件
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Log.v("onClick",position+"\t");
                if (onItemClickListener != null){
                    onItemClickListener.onItemClicked(getItem(position).getRightPosition());
                }
                for (LeftBean bean:mList){
                    bean.setSelect(false);
                }
                getItem(position).setSelect(true);
                notifyDataSetChanged();
            }
        });
    }

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

    public static class LeftViewHolder extends RecyclerView.ViewHolder {
        private final TextView tvTitle;
        //private View cl_left_item;


        LeftViewHolder(View itemView) {
            super(itemView);
            tvTitle = (TextView) itemView.findViewById(R.id.tv_title);

        }

    }

    interface OnItemClickListener {
        void onItemClicked(int rightPosition );
    }

    public void setCurrentPosition(int rightPosition){
        for (LeftBean bean:mList){
            if (bean.getRightPosition() == rightPosition){
                bean.setSelect(true);
            } else {
                bean.setSelect(false);
            }

        }
        notifyDataSetChanged();
    }

    public String getCurrentTitle(){
        String currentTitle = "";
        for (LeftBean bean:mList){
            if (bean.isSelect()){
                currentTitle = bean.getTitle();
                break;
            }
        }
        return currentTitle;
    }
}  

主要处理点击左边项目的选中状态，并将右边的小项的position回调出去给右边列表使用
其中LeftBean.class

public class LeftBean {
    //记录右边列表置顶项所在的item的位置
    private int rightPosition;
    private String title;
    //设置是否选中，改变背景色
    private boolean isSelect;

    public LeftBean(int rightPosition, String title) {
        this.rightPosition = rightPosition;
        this.title = title;
    }

    public boolean isSelect() {
        return isSelect;
    }

    public void setSelect(boolean select) {
        isSelect = select;
    }

    public int getRightPosition() {
        return rightPosition;
    }

    public void setRightPosition(int rightPosition) {
        this.rightPosition = rightPosition;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }
}  

三、项目结构图

select_goods_jiegou.png