c++ - SDL PollEvent() 从不返回任何内容

Question

我正在尝试让 SDL 检测 OS X 上 C++ 控制台应用程序/游戏的键盘事件。但不仅是 SDL_PollEvent() 没有返回任何键盘事件，据我所知通过调试它应该更新的 SDL_Event* 根本不会更新。我使用 SDL 的经验相当于网络上几分钟的教程，所以我确信在设置 SDL 时我没有做正确的事情导致了这个问题。下面是我编写的管理事件轮询的类，应该在检测到请求的按键时通过回调通知对象(参见 listenForKeyEvents())。但是，由于它依赖于 SDL_PollEvent()，因此它目前根本没有做任何事情。

using namespace std ;

template<class T>
struct KeyInputRegister {

    /**
     * The string representing the keyboard key
     * the client wishes to listen for
     */
    const char * requestedChar ;

    T * caller ;

    /**
     * A pointer to the function to be called
     * when the requested keyboard input is detected.
     */
    void (T::*callBack)() ;

    KeyInputRegister(const char* ch, T * callr, void (T::*cb)()) :
        requestedChar(ch), caller(callr), callBack(cb) {}

} ;

template <class T>
class InputController {

protected:
    static SDL_Event * event ;
    static std::thread * keyEventsThread ;

    static vector<KeyInputRegister<T>> * keyInputRegistry ;

    static void listenForKeyEvents() ;
    static void listenForKeyEvents_thread_start() ;

public:

    static void init() ;
    static void registerForKeypress(KeyInputRegister<T> & reg) ;
    static void exit() ;
} ;

template <class T>
void InputController<T>::init() {
    SDL_Init(SDL_INIT_EVERYTHING) ;
    keyInputRegistry = new vector<KeyInputRegister<T>> ;
    event = new SDL_Event() ;
    listenForKeyEvents_thread_start() ; 
}

template <class T>
void InputController<T>::listenForKeyEvents_thread_start() {
    void (*listenPtr)() = InputController<T>::listenForKeyEvents ;
    InputController<T>::keyEventsThread = new std::thread(listenPtr) ;
}

template <class T>
void InputController<T>::registerForKeypress(KeyInputRegister<T> & reg) {
    keyInputRegistry->push_back(reg) ;
}

template <class T>
void InputController<T>::listenForKeyEvents() {

    while (*GLOBAL_CONTINUE_SIGNAL) {
        if (SDL_PollEvent(event) == 1) {
            cout << "event detected!" << endl ;
            if (event->type == SDL_KEYDOWN) {

                auto key = event->key.keysym.sym ;
                const char * ch = SDL_GetKeyName(key) ;

                for (auto i = 0 ; i < keyInputRegistry->size() ; i++) {
                    if (ch == (keyInputRegistry->at(i).requestedChar)) {

                        T * callr = keyInputRegistry->at(i).caller ;

                        void (T::*callBak)() = (keyInputRegistry->at(i).callBack) ;

                        (callr->*callBak)();

                    }
                }
            }
        }
    }
}


/* An example use of KeyInputRegister and InputController: */

class GameObject {
    void moveForward() { cout << "moved forward!" << endl ; }

    void mfRegForCallback() {
        void (GameObject::*mvForwPtr)() = &GameObject::moveForward ;
        KeyInputRegister<GameObject> regMvF("w", this, mvForwPtr) ;
        InputController<GameObject>::registerForKeypress(regMvF) ;
    }
}


extern bool * GLOBAL_CONTINUE_SIGNAL = new bool(true) ;

#ifdef __cplusplus
extern "C"
#endif
int main(int argc, char ** argv) {
    InputController<GameObject>::init() ;
    GameObject player0 ;
    player0.mfregForCallback() ;
    usleep(1e9) ;
    *GLOBAL_CONTINUE_SIGNAL = false ;
    //other cleanup, etc.
    return 0;
}

#ifdef main
#undef main
#endif
int main(int argc, char ** argv) {
    int r = SDL_main(argc, argv) ; /*actually calls the above main(), which is redefined by SDL to be   
                                   SDL_main() */
    return r ;
}

Answer 1

我在您的代码中没有看到任何对 SDL_Init 的调用，请查看 http://www.friedspace.com/cprogramming/sdlbasic.php它显示了一个非常基本的示例，说明应该如何设置 SDL 应用程序。在轮询事件之前，您必须确保 SDL 正确运行。