SDL_Surface未在此范围内声明

Question

我似乎遇到了使用SDL_Surface的问题。

这是我的头文件（CApp.h）：

#ifndef _CAPP_H_
    #define _CAPP_H_

#include <SDL.h>

class CApp {
    private:
        bool            Running;

        SDL_Surface*    Surf_Display;

    public:
        CApp();

        int OnExecute();

    public:
        bool OnInit();

        void OnEvent(SDL_Event* Event);

        void OnLoop();

        void OnRender();

        void OnCleanup();
};

#endif

这就是问题所在：

#include "CApp.h"

CApp::CApp() {
    Surf_Display = NULL;
    Running = true;
}

int CApp::OnExecute() {
    if(OnInit() == false) {
        return -1;
    }

    SDL_Event Event;

    while(Running) {
        while(SDL_PollEvent(&Event)) {
            OnEvent(&Event);
        }

        OnLoop();
        OnRender();
    }

    OnCleanup();

    return 0;
}

int main(int argc, char* argv[]) {
//Start SDL
    SDL_Init( SDL_INIT_EVERYTHING );

    //Quit SDL
    SDL_Quit();

    return 0;
    CApp theApp;

    return theApp.OnExecute();
}

错误说'Surf_Display' was not declared in this scope.