SDL中的输入(按下按键)

Question

我想知道如何在SDL中的while循环中检测按键或释放键.现在,我知道你可以使用像OnKeyPressed,OnKeyReleased,OnKeyHit等SDL获取事件,但我想知道如何构建像'KeyPressed'这样的函数,它返回一个布尔值,而不是一个事件.例:

while not KeyHit( KEY_ESC ) 
{
//Code here
}

Answer 1

我知道你已经选择了答案..但这里有一些实际的代码,我通常用一个数组来做.:)

首先在某处定义.

bool KEYS[322];  // 322 is the number of SDLK_DOWN events

for(int i = 0; i < 322; i++) { // init them all to false
   KEYS[i] = false;
}

SDL_EnableKeyRepeat(0,0); // you can configure this how you want, but it makes it nice for when you want to register a key continuously being held down

然后,创建一个键盘()函数,它将注册键盘输入

void keyboard() {
        // message processing loop
        SDL_Event event;
        while (SDL_PollEvent(&event)) {
            // check for messages
            switch (event.type) {
                // exit if the window is closed
            case SDL_QUIT:
                game_state = 0; // set game state to done,(do what you want here)
                break;
                // check for keypresses
            case SDL_KEYDOWN:
                KEYS[event.key.keysym.sym] = true;
                break;
            case SDL_KEYUP:
                KEYS[event.key.keysym.sym] = false;
                break;
            default:
                break;
            }
        } // end of message processing
}

然后当你真的想要使用键盘输入即handleInput()函数时,它可能看起来像这样:

void handleInput() {
    if(KEYS[SDLK_LEFT]) { // move left
        if(player->x - player->speed >= 0) {
            player->x -= player->speed;
        }
    }
    if(KEYS[SDLK_RIGHT]) { // move right
        if(player->x + player->speed <= screen->w) {
            player->x += player->speed;
        }
    }
    if(KEYS[SDLK_UP]) { // move up
        if(player->y - player->speed >= 0) {
            player->y -= player->speed;
        }
    }
    if(KEYS[SDLK_DOWN]) { // move down
        if(player->y + player->speed <= screen->h) {
            player->y += player->speed;
        }
    }
    if(KEYS[SDLK_s]) { // shoot 
        if(SDL_GetTicks() - player->lastShot > player->shotDelay) {
            shootbeam(player->beam);
        }
    }
    if(KEYS[SDLK_q]) {
        if(player->beam == PLAYER_BEAM_CHARGE) {
            player->beam = PLAYER_BEAM_NORMAL;
        } else {
            player->beam = PLAYER_BEAM_CHARGE;
        }
    }
    if(KEYS[SDLK_r]) {
        reset();
    }

    if(KEYS[SDLK_ESCAPE]) {
        gamestate = 0;
    }
}

当然,您可以轻松地完成您想要做的事情

while(KEYS[SDLK_s]) {
    // do something
    keyboard(); // don't forget to redetect which keys are being pressed!
}

**我网站上的更新版本:**为了不发布大量源代码,您可以在C++中查看支持的完整SDL Keyboard类

1. 单键输入
2. 同时键组合(按键以任何顺序按下)
3. 顺序键组合(按键按特定顺序按下)

http://kennycason.com/posts/2009-09-20-sdl-simple-space-shooter-game-demo-part-i.html(如果您有任何问题,请告诉我)

Answer 2

有一个 SDL 函数可以实现此目的：SDL_GetKeyboardState

检查左或右 CTRL 键是否被按下的示例：

const Uint8* state = SDL_GetKeyboardState(nullptr);

if (state[SDL_SCANCODE_LCTRL] || state[SDL_SCANCODE_RCTRL]) {
     std::cerr << "ctrl pressed" << std::endl;
}