I have a Player class and a Game class.

My Game.cpp has has a setPlayers method. It compiles without an error but when I use it in my main, it doesn't work and gives me segment,c++,oop"/>

时间戳

首页 > 解决方案 > 访问向量 from another class' method

I have a Player class and a Game class.

My Game.cpp has has a setPlayers method. It compiles without an error but when I use it in my main, it doesn't work and gives me segment

c++ - 访问向量 from another class' method

I have a Player class and a Game class.

My Game.cpp has has a setPlayers method. It compiles without an error but when I use it in my main, it doesn't work and gives me segment

问题描述

I have a Player class and a Game class.

My Game.cpp has has a setPlayers method. It compiles without an error but when I use it in my main, it doesn't work and gives me segmentation fault instead. Is it even possible to access a vector of another object from another object's method? main.cpp

#include "player.h"
#include "game.h"
#include <iostream>

int main(int argc, char *argv[]){
    Game one;
    std::cout << "Position names: \n";
    std::cout << "Factory:1, ";
    std::cout << "Distributor:2, ";

    bool player_check[4] = {0, 0, 0, 0};
    int role_choice;
    int player_count;

    while(1){
      Player p;
      jump_to_choice:
        std::cout << "Enter your position: ";
        std::cin >> role_choice;
        p.setRole(role_choice);
        if(player_check[p.getRole()-1] == 0){
          std::cout << "Hello" << std::endl;
          //Adding a player to the Player* vector defined in game.h (players)
          one.setPlayers(&p, p.getRole()-1);
          player_check[p.getRole()-1] = 1;
          player_count++;
        }
    }
}

Player.h:

#ifndef PLAYER_H
#define PLAYER_H

#include "iostream"

class Game;

class Player {

private:
    int role;
    Game* game;
public:

    void setRole(int role);

    int getRole();
};

#endif

Player.cpp

int Player::getRole() {
    return this->role;
}
void Player::setRole(int newRole) {
    std::cout << "setting role" << std::endl;
    this->role = role;
}

Game.h

#ifndef GAME_H
#define GAME_H

#include <vector>
#include <map>
#include <string>
#include <stddef.h>
#include <time.h>
#include <stdlib.h>

#include "shipment.h"
#include "order.h"
#include "player.h"

class Game
{

private:
  int gId;
  std::vector<Player*> players;
public:
  std::vector<Player*> getPlayers();
  void setPlayers(Player*, int);
};
#endif

Game.cpp

void Game::setPlayers(Player* player_arg, int p_position){
  players[p_position] = player_arg;
}

android Recyclerview removing item does not update adapter's get item count

I have a RecyclerView with swiping feature to reveal a delete and edit button.

I added: adapter.notifyItemRemoved(position) and this: adapter.notifyItemRangeChanged(0, adapter.getItemCount());

when the revealed delete button is clicked, the animation for removing the item works and The item is deleted from my database

BUT then the deleted item re-appears in my recyclerview. When I change activity and go back, to the activity with the recyclerview, the list that I should be seeing is good.

If I remove the "notifyItemRangeChanged" code, the list updates with the last item repeated.

I think it is my Adapter's getItemCount not properly updating. so what I tried differently was to call my method that generates the list in the first place. This did the trick BUT my remove item animation is gone now because I guess it just skips to re-generate the list....

Any ideas?

Thank you in advanced for your feedback!

****************** UPDATE - ADDING ADAPTER CLASS CODE **************** public class RVCategoryAdapter extends RecyclerView.Adapter { Context context; List categoryItemList;

    public RVCategoryAdapter(Context context, List<CategoryItem> categoryItemList) {
        this.context = context;
        this.categoryItemList = categoryItemList;
    }

    @NonNull
    @Override
    public CategoryViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(context).inflate(R.layout.category_item_layout, parent, false);

        return new CategoryViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull CategoryViewHolder holder, final int position) {
        final int categoryID;
        final String categoryTitle;

        Glide.with(context).load(categoryItemList.get(position).getImage()).into(holder.ivCategoryIcon);
        holder.txtCatID.setText(""+categoryItemList.get(position).getCategoryID());
        holder.txtCategoryTitle.setText(categoryItemList.get(position).getTitle());
        holder.txtCategoryDesc.setText(categoryItemList.get(position).getDescription());

        categoryID = Integer.parseInt(holder.txtCatID.getText().toString());
        categoryTitle = holder.txtCategoryTitle.getText().toString();
        holder.cardViewItemLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(context, NotesListActivity.class);
                intent.putExtra("CategoryID", categoryID);
                intent.putExtra("CategoryTitle", categoryTitle);
                context.startActivity(intent);
            }
        });
    }

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

标签： c++oop

解决方案

您发布的代码中有两个问题。

首先，向量从零大小开始，除非你构造一个非零大小的向量。您创建一个没有元素的向量，然后在这里

void Game::setPlayers(Player* player_arg, int p_position){
  players[p_position] = player_arg;
}

你operator[]用来访问元素。注意到什么了吗？您不能访问空向量中的元素。用于push_back在后面添加元素。实际上，如果您想让玩家在某些位置，那么 astd::unordered_map会更容易，它们可以用作“稀疏”数组，即即使这是您添加的第一个玩家，您也可以添加 a Playerat 。p_position = 12

第二，

one.setPlayers(&p, p.getRole()-1);

指针&p始终具有相同的值。它是本地对象的地址Player p;。当您离开作用域时，该对象将被销毁，并且向量中的所有指针都变为悬空指针。当您实际上想要一个对象容器时，将指针存储在容器中是一个常见的错误。改用 a std::vector<Player>。

推荐阅读