c++ - Visual C++ 和 Allegro5 : cannot recognize objects from abstract class from header file

Question

我是 allegro 的初学者，不太熟悉 C++，但我了解这门语言，所以我想编写一个国际象棋游戏。但是因为我想在这个游戏中使用图像，所以我研究了 Allegro 5 来对其进行编程。我想出了一个(当然不完整)头文件来初始化游戏中的每一个棋子:

片.h

#pragma once
#include <allegro5/allegro.h>
#include <allegro5/allegro_native_dialog.h>
#include <allegro5/allegro_primitives.h>
#include <allegro5/allegro_image.h>
#include <iostream>
#include <string>

using namespace std;

class Piece
{
    private:

        int pieceX;
        int pieceY;
        bool inGame;
        char pieceColor;
        string imgAddress;
        ALLEGRO_BITMAP *pieceImage;

    public:

        Piece(int pieceX, int pieceY, bool inGame, char pieceColor, string imgAddress)
        {
            this->pieceX = pieceX;
            this->pieceY = pieceY;
            this->inGame = inGame;
            this->pieceColor = pieceColor;
            this->imgAddress = imgAddress;
            pieceImage = al_load_bitmap(imgAddress.c_str());
        }

        int getPieceX()
        {
            return pieceX;
        }

        int getPieceY()
        {
            return pieceY;
        }

        bool isInGame()
        {
            return inGame;
        }

        char getPieceColor()
        {
            return pieceColor;
        }

        string getImageAddress()
        {
            return imgAddress;
        }

        void setPieceX(int newx)
        {
            pieceX = newx;
        }

        void setPieceY(int newy)
        {
            pieceY = newy;
        }

        void setinGame(bool newingame)
        {
            inGame = newingame;
        }

        void setImageAddress(string newimgaddr)
        {
            imgAddress = newimgaddr;
        }

        void reloadImage()
        {
            pieceImage = al_load_bitmap(imgAddress.c_str());
        }

        Piece(void)
        {

        }

        ~Piece(void)
        {

        }

};

其他一切都将在主类 Chess.cpp 中处理

#include <allegro5/allegro.h>
#include <allegro5/allegro_native_dialog.h>
#include <allegro5/allegro_primitives.h>
#include <allegro5/allegro_image.h>
#include "Piece.h"
#include <iostream>
#include <string>
#include <cstring>

using namespace std;

const int SIDELENGTH = 50;
const int ROWCOLSPAN = 8;
const int WINDOW_WIDTH = (SIDELENGTH * ROWCOLSPAN) + 240;
const int WINDOW_HEIGHT = (SIDELENGTH * ROWCOLSPAN) + 40; 
const float FPS = 60;
const int MAXPIECES = ROWCOLSPAN * 2;
const int MAXSPACES = ROWCOLSPAN * ROWCOLSPAN;

setupBoard(Piece [MAXPIECES], Piece [MAXPIECES], char [MAXSPACES]);

int main()
{
    ALLEGRO_DISPLAY *gameDisplay;

    if (!al_init()) cout << "Failed to load Allegro 5 for Chess++..." << endl;

    gameDisplay = al_create_display(WINDOW_WIDTH, WINDOW_HEIGHT);
    al_set_window_title(gameDisplay, "Chess++");

    if (!gameDisplay) cout << "Couldn't create Allegro 5 display for Chess++..." << endl;

    al_init_primitives_addon(); //allows to load primitives
    al_install_keyboard(); //allows for keyboard use*/
    al_install_mouse(); //installs the mouse to be able to use it
    al_init_image_addon(); //prepares image loading

    ALLEGRO_EVENT_QUEUE *gameQueue = al_create_event_queue(); //queue that receives events and acts them in order
    al_register_event_source(gameQueue, al_get_keyboard_event_source()); //registers keyboard events to be recognized within event_queue

    ALLEGRO_KEYBOARD_STATE keyState;
    ALLEGRO_TIMER *gameTimer = al_create_timer(1.0 / FPS);

    al_register_event_source(gameQueue, al_get_keyboard_event_source()); //registers keyboard events to be recognized within event_queue
    al_register_event_source(gameQueue, al_get_timer_event_source(gameTimer)); //registers a timer to work within event_queue
    al_register_event_source(gameQueue, al_get_display_event_source(gameDisplay)); //registers the window to be able to give it events
    al_register_event_source(gameQueue, al_get_mouse_event_source()); //register the installed mouse

    bool gameOver = false;
    bool draw = false;
    bool quitclose = false;

    int X = 0;
    int Y = 0;

    Piece blackPieces[MAXPIECES];
    Piece whitePieces[MAXPIECES];

    //The 8 by 8 board with the pieces; lowercase for black, uppercase for white
    char chessboard[] = "rnbqkbnr\n"
                        "pppppppp\n" 
                        "--------\n"
                        "--------\n"
                        "--------\n"
                        "--------\n"
                        "--------\n"
                        "PPPPPPPP\n"
                        "RNBQKBNR";

    //setupBoard(blackPieces, whitePieces, chessboard);

    al_start_timer(gameTimer); //starts the specified timer

    gameloop:
    while(!gameOver)
    {
        ALLEGRO_EVENT gameEvents; //create receiver for events
        al_wait_for_event(gameQueue, &gameEvents); //waits for an event from event_queue to be passed on to ALLEGRO_EVENT events

        if (gameEvents.type == ALLEGRO_EVENT_KEY_UP/*DOWN*/)
        {

        }
        else if (gameEvents.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
        {
            quitclose = true;
            gameOver = true;
        }
        else if (gameEvents.type == ALLEGRO_EVENT_MOUSE_AXES) //determines the movement of the mouse coordinates
        {

        }
        else if (gameEvents.type == ALLEGRO_EVENT_MOUSE_BUTTON_DOWN) //if a mouse button is pressed
        {

        }

        if (gameEvents.type == ALLEGRO_EVENT_TIMER)
        {
            draw = true;
        }

        if (draw)
        {
            draw = false;

            int squareX = 20;
            int squareY = 20;
            bool colorchange = true;
            for (int i = 1; i <= MAXSPACES;i++)
            {               
                ALLEGRO_COLOR squarecolor = al_map_rgb(255, 255, 255);
                if (!colorchange) squarecolor = al_map_rgb(0, 100, 0);

                al_draw_filled_rectangle(squareX, squareY, squareX + SIDELENGTH, squareY + SIDELENGTH, squarecolor);
                squareX += SIDELENGTH;
                if (i % ROWCOLSPAN != 0) colorchange = !colorchange;

                if (i % ROWCOLSPAN == 0)
                {
                    squareY += SIDELENGTH;
                    squareX = 20;
                }

            }

            al_flip_display();          
            al_clear_to_color(al_map_rgb(0, 0, 0)); //clears the canvas (display) like Java's repaint()
        }

    }

    if (quitclose)
    {
        int quit = al_show_native_message_box(gameDisplay, "CHES++: QUIT", "ARE YOU SURE YOU WANNA QUIT?", "Please select YES or NO", NULL, ALLEGRO_MESSAGEBOX_YES_NO);
        if (quit == 0)
        {
            gameOver = false;
            goto gameloop;
        }
    }

    al_destroy_display(gameDisplay);

    /*cin.sync();
    cout << "\n\nPress any key to finish...";
    cin.get();*/
    return 0;
}

void setupBoard(Piece bp[MAXPIECES], Piece wp[MAXPIECES], char cb[])
{
    int barrindex = 0;
    int warrindex = 0;
    int x = 20;
    int y = 20;

    for (int i = 0; i < MAXSPACES; i++)
    {
        if (cb[i] == 'r')
        {
            bp[barrindex] = new Piece(x, y, true, 'b', "images/br.png");
            barrindex++;
            x += SIDELENGTH;
        }     
        if (cb[i] == 'n')
        {
            bp[barrindex] = new Piece(x, y, true, 'b', "images/bn.png");
            barrindex++;
            x += SIDELENGTH;
        }
        if (cb[i] == 'b')
        {
            bp[barrindex] = new Piece(x, y, true, 'b', "images/bb.png");
            barrindex++;
            x += SIDELENGTH;
        }
        if (cb[i] == 'q')
        {
            bp[barrindex] = new Piece(x, y, true, 'b', "images/bq.png");
            barrindex++;
            x += SIDELENGTH;
        }
        if (cb[i] == 'k')
        {
            bp[barrindex] = new Piece(x, y, true, 'b', "images/bk.png");
            barrindex++;
            x += SIDELENGTH;
        } 
        if (cb[i] == 'p')
        {
            bp[barrindex] = new Piece(x, y, true, 'b', "images/bp.png");
            barrindex++;
            x += SIDELENGTH;
        }
        if (cb[i] == 'R')
        {
            wp[warrindex] = new Piece(x, y, true, 'w', "images/wr.png");
            warrindex++;
            x += SIDELENGTH;
        }     
        if (cb[i] == 'N')
        {
            wp[warrindex] = new Piece(x, y, true, 'w', "images/wn.png");
            warrindex++;
            x += SIDELENGTH;
        }
        if (cb[i] == 'B')
        {
            wp[warrindex] = new Piece(x, y, true, 'w', "images/wb.png");
            warrindex++;
            x += SIDELENGTH;
        }
        if (cb[i] == 'Q')
        {
            wp[warrindex] = new Piece(x, y, true, 'w', "images/wq.png");
            warrindex++;
            x += SIDELENGTH;
        }
        if (cb[i] == 'K')
        {
            wp[warrindex] = new Piece(x, y, true, 'w', "images/wk.png");
            warrindex++;
            x += SIDELENGTH;
        } 
        if (cb[i] == 'P')
        {
            wp[warrindex] = new Piece(x, y, true, 'w', "images/wp.png");
            warrindex++;
            x += SIDELENGTH;
        }
        if (cb[i] == '-')
        {
            x += SIDELENGTH;
        } 
        if (cb[i] == '\n')
        {
            y += SIDELENGTH;
            x = 20;
        }
    }
}

在添加 setupBoard() 函数和两个 Piece 对象(blackPieces 和 whitePieces)之前，我的程序会运行，并且会显示一个漂亮的“棋盘”，它基本上是使用 allegro 的原始库绘制的 64 个正方形，所以我认为我已经正确安装了库和驱动程序。然而，我得到的错误超出了我的范围:

1. 首先，setupBoard是一个void，只是为了修改其他变量来组织代码。然而 Intellisense 给我一个错误:this declaration has no storage class or type specifier

2. #include "Piece.h" 没有出现错误，但是在数组 blackPieces 和 whitePieces 的声明中，我得到了 identifier "Piece"is未定义

3. 在 Chess.cpp 底部的 setupBoard 函数中，我通读了来自棋盘的字符数组 cb，它具有用于在棋盘中放置棋子的特定字符。并且根据哪个字符，一个 Piece 对象被动态分配到它各自的 Piece 数组中，像这样:

bp[barrindex] = new Piece(x, y, true, 'b', "images/br.png");

然后控制板的 x 和 y 的整数相应地递增以将它们绘制在不同的位置。然而，虽然除了 new Piece( 之外似乎没有错误，我猜这是因为错误 2，但我得到了这个错误:

error C2679: binary '=' : no operator found which takes a right-hand operand of type 'Piece *' (or there is no acceptable conversion)

我确定我一定是分配错误，但我不知道怎么回事，我从来没有遇到过这种错误。现在，我总是可以尝试用 Java 或 C# 做国际象棋游戏，但我想用 C++ 做某种游戏(我认为制作 AI 的逻辑与语言知识没有任何关系)。拜托，如果有人知道如何解决这些错误，我将非常感激!!

Answer 1

setupBoard(Piece [MAXPIECES], Piece [MAXPIECES], char [MAXSPACES]);

你需要在它前面有一个 void。

这些是不同的东西:

Piece bp[MAXPIECES]
Piece* bp[MAXPIECES]

按照你的方式，你需要这样做:

wp[warrindex] = Piece(x, y, true, 'w', "images/wn.png");

要了解两者之间的区别，请阅读堆栈与堆内存分配。您真的可能想通过 Piece* bp[MAXPIECES] 使用堆并保持您的 new 调用。