窗口无法加载-c ++ / SDL

Question

I'm very new with SDL. I'm trying to add an image to a window and I have followed this tutorial: http://lazyfoo.net/SDL_tutorials/lesson02/index.php

I'm doing all the code in xcode and when I run it the window won't load. I just flashes up and then dissapear and I know I've done all the steps I should. This is my code:

const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;

SDL_Surface *message = NULL;
SDL_Surface *background = NULL;
SDL_Surface *screen = NULL;

SDL_Surface *load_image(std::string filename)
{
    SDL_Surface *loadedImage = NULL;
    SDL_Surface *optimizedImage = NULL;

    loadedImage = SDL_LoadBMP( filename.c_str() );

    if (loadedImage != NULL)
    {
        optimizedImage = SDL_DisplayFormat(loadedImage);
        SDL_FreeSurface(loadedImage);

    }

    return optimizedImage;
}

void apply_surface(int x, int y, SDL_Surface *source, SDL_Surface *destination)
{
    SDL_Rect offset;

    offset.x = x;
    offset.y = y;

    SDL_BlitSurface(source, NULL, destination, &offset);
}



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

    //Quit SDL
    SDL_Quit();

    if (SDL_Init(SDL_INIT_EVERYTHING)==-1)
    {
        return 1;
    }

    screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);

    if (screen == NULL)
    {
        return 1;
    }

    SDL_WM_SetCaption("Hellow world!", NULL);

    message = load_image("images.bmp");
    background = load_image("images.bmp");

    apply_surface(0, 0, background, screen);

    apply_surface(180, 140, message, screen);

    return 0;

}

Answer 1

You are prematurely invoking SDL_Quit() in the main function. This function shuts down all SDL subsystems and should instead be called at the end of your program.

If you wish for the window to remain until you close it explicitly, add a loop such as the following:

int main() {
  if (SDL_Init(SDL_INIT_EVERYTHING) == -1) {
    return 1;
  }

  screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);
  if (!screen) {
    return 1;
  }

  bool running = true;

  SDL_Event event;
  while (running) {
    while (SDL_PollEvent(&event)) {
      if (event.type == SDL_QUIT) {
        running = false;
      }
    }
  }

  SDL_Quit();
  return 0;
}

You can set running to false when some event occurs, such as when the window is closed.

Answer 2

you have put SDL_Quit(); at the very start of your program. This is like putting return 0; before all your code. It shuts down when it reads that line. To avoid this you should make a loop that breaks when the 'x' at the top of the window it pressed.