c++ - 奇怪的基本 SDL

Question

我刚开始学习 SDL，我发现如果我初始化一个 SDL_Rect 变量，SDL_Delay 不起作用。然后，如果我在 SDL_Rect 中设置其中一个值，图像甚至不会显示(或暂停)。我不明白。我从 lazyfoo 的教程中获得了这段代码，目前我只是在弄乱它

#include <SDL/SDL.h>
#include <iostream>

using namespace std;
int main( int argc, char* args[] ){

    int width = 512;
    int height = 512;

    //The images
    SDL_Surface* source = NULL;
    SDL_Surface* screen = NULL;
    //Start SDL
    //SDL_Init( SDL_INIT_EVERYTHING );
    if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 ) {
        return 1;
    }
    //Set up screen
    screen = SDL_SetVideoMode( width, height, 24, SDL_SWSURFACE );

    //Load imagec
    source = SDL_LoadBMP( "image.bmp");
    //Apply image to screen

    SDL_Rect * hello;                    //here is where it messes up the program 
    //for(int a = 0; a < width; a++){    // i was trying to make the image move around the screen/window
    //hello -> x = 0;
    //now -> w = 200;
    //now -> h = 200;
    //for(int b = 0; b < height; b++){
    //now -> y = 0;
    //SDL_WM_SetCaption( "ajsncnsc", NULL );
    SDL_BlitSurface( source, NULL, screen, NULL );
    //Update Screen
    SDL_Flip( screen );
    SDL_Delay( 2000 );
    //    }
    //}

    //Free the loaded image
    SDL_FreeSurface( source );
    //Quit SDL
    SDL_Quit();
    return 0;
}

Answer 1

SDL_Rect * hello; 创建一个指向 SDL_Rect 的指针。它指向随机内存，因为您没有为它分配任何东西。修改其成员可能会导致任何事情发生。

改用 SDL_Rect hello; - 这会创建一个实际的 SDL_Rect，您现在可以安全地进行操作，例如hello.x = 200; 无需修改您不拥有的内存。