android RecyclerView实现查看更多及收起

看到这个需求下面评论还挺多的，自己就写了个demo 但处理方式和下面这个方法不一样，下面的方法是在外部处理list 设置了三个数据源，觉得每次用这个适配器都需要这么设置数据源很麻烦，还要在外部处理点击，就把逻辑封装到适配器内部处理了 具体逻辑可以见第二种方式代码

第一种方式：

三个list：

• realList 真实list
• hideList 隐藏时的list
• openList 展开时的list

做法就是

• 判断适配器条目小于4（可任意）时，将适配器list设置为真实list
• 判断适配器条目大于4（可任意）时，将适配器hideList设置为真实list的前三个条目+查看更多；将适配器openList设置为真实list+收起

适配器代码

public class LuckyCodeAdapter extends RecyclerView.Adapter<LuckyCodeAdapter.LuckyCodeViewHolder> {
    private Context context;
    private List<String> list;
    private boolean isHide;//隐藏
    private boolean isOpen;//展开

    public LuckyCodeAdapter(Context context) {
        this.context = context;
    }

    @Override
    public LuckyCodeViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(context).inflate(R.layout.item_tosanpup_lucky_code, parent, false);
        return new LuckyCodeViewHolder(v);
    }

    @Override
    public void onBindViewHolder(LuckyCodeViewHolder holder, final int position) {
        holder.txtLuckyCode.setText(list.get(position));
        if (hideOrShowCallBack != null) {
            holder.txtLuckyCode.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (position == list.size() - 1) {
                        if (isOpen) {
                            hideOrShowCallBack.hide();
                            return;
                        }
                        if (isHide) {
                            hideOrShowCallBack.open();
                            return;
                        }
                    }
                }
            });

        }
    }

    @Override
    public int getItemCount() {
        return list == null ? 0 : list.size();
    }

    //隐藏
    public void setHideList(List<String> newList) {
        this.list = newList;
        notifyDataSetChanged();
        this.isHide = true;
        this.isOpen = false;
    }

    //展开
    public void setOpenList(List<String> openList) {
        this.list = openList;
        this.isOpen = true;
        this.isHide = false;
        notifyDataSetChanged();
    }

    //不需要隐藏/展开
    public void setRealList(List<String> realList) {
        this.list = realList;
        notifyDataSetChanged();
        this.isHide = false;
        this.isOpen = false;
    }

    //清除数据
    public void clearData() {
        if (list != null) {
            this.list.clear();
            notifyDataSetChanged();
        }
    }

    class LuckyCodeViewHolder extends RecyclerView.ViewHolder {
        TextView txtLuckyCode;//幸运号码

        public LuckyCodeViewHolder(View itemView) {
            super(itemView);
            txtLuckyCode = (TextView) itemView;
        }
    }

    private HideOrShowCallBack hideOrShowCallBack;

    public void setHideOrShowCallBack(HideOrShowCallBack hideOrShowCallBack) {
        this.hideOrShowCallBack = hideOrShowCallBack;
    }

    public interface HideOrShowCallBack {
        void hide();

        void open();
    }
}

//luckyList为真实list，判断是否需要隐藏
  if (luckyList.size() > 4) {
            luckyCodeHideList = new ArrayList<>();
            luckyCodeOpenList = new ArrayList<>();
            for (int i = 0; i < luckyList.size(); i++) {
                luckyCodeOpenList.add(luckyList.get(i));
            }
            luckyCodeOpenList.add("收起");

            for (int i = 0; i < 3; i++) {
                luckyCodeHideList.add(luckyList.get(i));
            }
            luckyCodeHideList.add("查看更多");
            luckyCodeAdapter.setHideList(luckyCodeHideList);
        } else {
            luckyCodeAdapter.setRealList(luckyList);
        }

设置监听

luckyCodeAdapter.setHideOrShowCallBack(new LuckyCodeAdapter.HideOrShowCallBack() {
            @Override
            public void hide() {
                luckyCodeAdapter.setHideList(luckyCodeHideList);
            }

            @Override
            public void open() {
                luckyCodeAdapter.setOpenList(luckyCodeOpenList);
            }
        });

第二种方式：

recyclerView = findViewById(R.id.recycler_view);
List<String> list = new ArrayList<>();
for (int i = 0; i < 30; i++) {
    list.add("10000000" + i);
}
SeeMoreAdapter seeMoreAdapter = new SeeMoreAdapter(list);
recyclerView.setLayoutManager(new GridLayoutManager(this, 4));
recyclerView.setAdapter(seeMoreAdapter);

class SeeMoreAdapter extends RecyclerView.Adapter<SeeMoreAdapter.SeeMoreViewHolder> {

    private final static int TYPE_NORMAL = 0;//正常条目
    private final static int TYPE_SEE_MORE = 1;//查看更多
    private final static int TYPE_HIDE = 2;//收起
    private List<String> mList;
    private boolean mOpen = false;//是否是展开状态

    SeeMoreAdapter(List<String> mList) {
        this.mList = mList;
    }

    @NonNull
    @Override
    public SeeMoreViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item_view, viewGroup, false);
        return new SeeMoreViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull SeeMoreViewHolder seeMoreViewHolder, int position) {
        TextView textView = (TextView) seeMoreViewHolder.itemView;
        if (getItemViewType(position) == TYPE_HIDE) {
            textView.setText("收起");
            textView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mOpen = false;
                    notifyDataSetChanged();
                }
            });
        } else if (getItemViewType(position) == TYPE_SEE_MORE) {
            textView.setText("查看更多");
            textView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mOpen = true;
                    notifyDataSetChanged();
                }
            });
        } else {
            textView.setText(mList.get(position));
            textView.setClickable(false);
        }
    }

    @Override
    public int getItemViewType(int position) {
        if (mList.size() <= 4) {
            return TYPE_NORMAL;
        }
        if (mOpen) {
            if (position == mList.size()) {
                return TYPE_HIDE;
            } else {
                return TYPE_NORMAL;
            }
        } else {
            if (position == 3) {
                return TYPE_SEE_MORE;
            } else {
                return TYPE_NORMAL;
            }
        }
    }

    @Override
    public int getItemCount() {
        if (mList == null || mList.size() == 0) {
            return 0;
        }
        if (mList.size() > 4) {
            //若现在是展开状态 条目数量需要+1 "收起"条目
            if (mOpen) {
                return mList.size() + 1;
            } else {
                return 4;
            }
        } else {
            return mList.size();
        }
    }

    class SeeMoreViewHolder extends RecyclerView.ViewHolder {

        public SeeMoreViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }
}

请接受我双手奉上的源码