如何知道在SDL2中按下了哪些键

#include <SDL2/SDL.h>

int main() {
    // 初始化SDL2库
    SDL_Init(SDL_INIT_VIDEO);

    // 创建窗口和渲染器
    SDL_Window* window = SDL_CreateWindow("SDL2 Keyboard Input", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 800, 600, SDL_WINDOW_SHOWN);
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, 0);

    // 事件循环
    SDL_Event event;
    bool quit = false;
    while (!quit) {
        // 获取事件
        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT) {
                quit = true;
            } else if (event.type == SDL_KEYDOWN) {
                // 判断按键
                switch (event.key.keysym.sym) {
                    case SDLK_LEFT:
                        printf("Left arrow key pressed\n");
                        break;
                    case SDLK_RIGHT:
                        printf("Right arrow key pressed\n");
                        break;
                    case SDLK_a:
                        printf("A key pressed\n");
                        break;
                    case SDLK_b:
                        printf("B key pressed\n");
                        break;
                    // 其他按键的判断...
                }
            }
        }

        // 渲染画面
        SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
        SDL_RenderClear(renderer);
        SDL_RenderPresent(renderer);
    }

    // 清理资源
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}