已定义/多个对象定义/可视化工作室

我正在关注 SDL 上的视频图。当我完全按照他的做法做时，通过在 Game.h 中放置一个 SDL_Texture* 并在 Game.cpp 中使用对象，我会收到有关多个定义的错误。然而，视频创作者没有这样的错误。但是，我可以将SDL_Texture*复制并粘贴到.cpp，它工作得很好。

为什么相同的代码可以在Visual Studio中的一台机器上工作，而不是另一台机器

游戏.cpp

#include "Game.h"

Game::Game()
{

}
Game::~Game()
{

}
void Game::init(const char* title, int xpos, int ypos, int width, int height, bool fullscreen)
{
int flags = 0;
if (fullscreen)
{
flags = SDL_WINDOW_FULLSCREEN;
}
if (SDL_Init(SDL_INIT_EVERYTHING) == 0)
{
std::cout << "Successfully Initialized Subsystem . . . " << std::endl;
window = SDL_CreateWindow(title, xpos, ypos, width, height, flags);
if (window)
{
std::cout << "Successfully Created Window . . . " << std::endl;
}
else
{
std::cout << "Something went wrong. Error: " << SDL_GetError() << std::endl;
}
renderer = SDL_CreateRenderer(window, -1, 0);
if (renderer)
{
SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
std::cout << "Successfully Created Renderer . . . " << std::endl;
}
else
{
std::cout << "Something went wrong. Error: " << SDL_GetError() << std::endl;
}
is_running = true;
}
else
{
is_running = false;
}
SDL_Surface* surf_temp = IMG_Load("assets/player.png");
tex_player = SDL_CreateTextureFromSurface(renderer, surf_temp);
SDL_FreeSurface(surf_temp);

}

void Game::event_handle()
{
SDL_Event event;
SDL_PollEvent(&event);
switch (event.type)
{
case SDL_QUIT:
is_running = false;
}
}
void Game::update()
{
cnt++;
std::cout << cnt << std::endl;

}

void Game::render()
{
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, tex_player, NULL, NULL); 
SDL_RenderPresent(renderer);
}
void Game::clean()
{
SDL_DestroyWindow(window);
SDL_DestroyRenderer(renderer);
SDL_Quit();
std::cout << "Game cleaned . . . " << std::endl;
}

游戏.h

#include "SDL.h"
#include "SDL_image.h"
#include <iostream>
#include <stdio.h>
#include <string>

SDL_Texture* tex_player;
class Game 
{
public:
Game();
~Game();
void init(const char* title, int xpos, int ypos, int width, int height, bool fullscreen);
void event_handle();
void update();
void render();
void clean();
bool running() { return is_running; }

private:
int cnt;
bool is_running;
SDL_Window *window;
SDL_Renderer *renderer;

};

主.cpp

#include "Game.h"

Game *game = nullptr;
int main(int argc, char *argv[])
{
game = new Game();
game->init("Yeah", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 800, 600, false);
while (game->running())
{
game->event_handle();
game->update();
game->render();
}
game->clean();
return 0;
}

错误：

1>------ Build started: Project: SDL_Template, Configuration: Debug Win32 ------
1>main.cpp
1>LINK : C:UsersOniondocumentsvisual studio 2017ProjectsSDL_TemplateDebugSDL_Template.exe not found or not built by the last incremental link; performing full link
1>main.obj : error LNK2005: "struct SDL_Texture * tex_player" (?tex_player@@3PAUSDL_Texture@@A) already defined in Game.obj
1>C:UsersOniondocumentsvisual studio 2017ProjectsSDL_TemplateDebugSDL_Template.exe : fatal error LNK1169: one or more multiply defined symbols found
1>Done building project "SDL_Template.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========