C 类获取错误(SDL）

C++ classes getting error (SDL)

本文关键字：SDL 取错误 获取      更新时间：2023-10-16

可能的重复：
什么是未定义的参考/未解决的外部符号错误，我该如何修复？

嗨，我是上课的菜鸟，我才开始学习它们。我需要此代码的帮助，因为我不知道为什么会遇到此错误。

这是我的代码

main.cpp 

    #include "stdafx.h"
    #include "player.h"

SDL_Surface* screen = NULL;
void init()
{
    SDL_Init( SDL_INIT_VIDEO );
    //Set up screen
    screen = SDL_SetVideoMode( 640, 480, 32,  SDL_DOUBLEBUF |SDL_HWSURFACE |SDL_SWSURFACE);
    //SDL_BlitSurface( hello, NULL, screen, NULL );
        _putenv("SDL_VIDEO_CENTERED=1"); // Center the window 
    SDL_Init(SDL_INIT_VIDEO);
    SDL_WM_SetCaption("SDL Animation", "SDL Animation");
    //screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, 0, SDL_DOUBLEBUF |SDL_HWSURFACE |SDL_SWSURFACE);
    SDL_EnableKeyRepeat(0, 1600000);
    if(screen == NULL){
         printf("SDL_Init failed: %sn", SDL_GetError());
    }

}
int _tmain(int argc, _TCHAR* argv[])
{   
    init();
    //SDL_Surface* sprite = SDL_BlitSurface(sprite,rcSprite, screen, &rcSprite);
    Player player;

    //Update Screen
    SDL_Flip( screen );
    SDL_FreeSurface(screen); 
    return 0;
}

player.h 

    #ifndef PLAYER_H
#define PLAYER_H
#include "SDL.h"
#include "SDL_image.h"
#include "SDL_TTF.h"
class Player
{
public:
    Player (){
        HP = 20;
        playerScore = 0;
        playerSpeed = 10;
        playerJump = 20;
    }
    ~Player();
    int getScore() { return playerScore;}
    void setSpeed(int speed) { int playerSpeed = speed;}
    void setJump (int jump) {playerJump = jump;}
    void movePlayer(int x ,int y);
    void runRightAnim (SDL_Rect* clip);
    void runLeftAnim (SDL_Rect* clip);
    void drawPlayer(int x, int y, SDL_Surface* source, SDL_Surface* destination);
    static SDL_Rect sprite;
private:
    static int HP;
    static int playerScore;
    static int playerSpeed;
    static int playerJump;
    static int animRate;
};
#endif

和最后一个玩家。CPP

    #include "stdafx.h"
#include "SDL.h"
#include "SDL_image.h"
#include "SDL_TTF.h"
#include "player.h"
void Player::runRightAnim(SDL_Rect* clip)
{
}
void Player::runLeftAnim(SDL_Rect* clip)
{
}
void Player::drawPlayer(int x, int y, SDL_Surface* source, SDL_Surface* destination)
{
     SDL_Rect dst;
          dst.x = x;
          dst.y = y;
     SDL_BlitSurface(source,NULL,destination,&dst);
     //SDL_BlitSurface(selectionCanvas, NULL, canvas, selectionRect);
}

错误是

1>main.obj : error LNK2019: unresolved external symbol "public: __thiscall Player::~Player(void)" (??1Player@@QAE@XZ) referenced in function _wmain
1>main.obj : error LNK2001: unresolved external symbol "private: static int Player::playerJump" (?playerJump@Player@@0HA)
1>main.obj : error LNK2001: unresolved external symbol "private: static int Player::playerSpeed" (?playerSpeed@Player@@0HA)
1>main.obj : error LNK2001: unresolved external symbol "private: static int Player::playerScore" (?playerScore@Player@@0HA)
1>main.obj : error LNK2001: unresolved external symbol "private: static int Player::HP" (?HP@Player@@0HA)

代码显然没有完成，但我只想摆脱此错误

"未解决的外部"错误在您声明和尝试使用函数时会发生，但您不实现它。特别是：

1> main.obj：错误lnk2019：未解决的外部符号"公共： __ thiscall player ::〜播放器（void）"（?? 1player @@ qae@xz）在功能中引用_wmain

是因为尽管您有Player::~Player()的声明：

class Player
{
public:
  /* ... */
    ~Player();

从未实现此方法。

通过实现所讨论的方法来修复此错误。

编辑：此外，您的类具有静态成员变量，这些变量已声明但从未定义。您的声明在这里：

class Player
{
/* ...  */
private:
    static int HP;
    static int playerScore;
    static int playerSpeed;
    static int playerJump;
    static int animRate;
};

，但此声明并未定义变量。您必须定义和初始化这些静态，否则您也将得到（正在得到）未解决的外部。

通常在CPP文件中的某个地方：

int Player::playerScore = 0;

顺便说一句，您正在使用static成员变量作为类，该类似乎多次可以让您有效。如果这样做：

Player a;
Player b;

要实例化多个Player对象，因为将成员变量声明为static，它们每个人都会"共享"相同的playerScore等。在查看您的代码时，这并没有很多意义。您可能不希望这些是statics。

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