如何使用C在SDL2中移动矩形

时间:2016-01-29 12:00:19

标签: c events sdl-2

我无法移动我在程序中制作的矩形。运行程序时,编译器中没有错误消息。你能告诉我在键盘事件中我错过了什么。我分配给窗口的其他事件工作正常。你可以告诉我解决方案,而不是写下指令。我一直在这。感谢

#include <SDL.h>
#include <stdlib.h>

int main()
{
    SDL_Window *o;
    SDL_Renderer *r;
    SDL_Event e;
    SDL_Rect q;
    int i =1;

    SDL_Init(SDL_INIT_VIDEO);

    o = SDL_CreateWindow("Game test",
                            SDL_WINDOWPOS_UNDEFINED,
                            SDL_WINDOWPOS_UNDEFINED,
                            1024,
                            800,
                            SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);

    r = SDL_CreateRenderer(o, -1,SDL_RENDERER_ACCELERATED);

    while(i)
    {
        while(SDL_PollEvent(&e) !=0)
        {
            if(e.type == SDL_QUIT)
                i=0;
            else if(e.type == SDL_KEYDOWN)
            {
                switch(e.key.keysym.sym)
                {
                case SDLK_ESCAPE:
                case SDLK_q:
                    i=0;
                break;
                case SDLK_UP:
                    q.y -=10;
                break;
                case SDLK_DOWN:
                    q.y +=10;
                break;
                case SDLK_RIGHT:
                    q.x +=10;
                break;
                case SDLK_LEFT:
                    q.x -=10;
                break;
                }
            }
        }
        SDL_SetRenderDrawColor(r,0,0,255,255);
        SDL_RenderClear(r);
        // Creating the rectangle
        q.x=475;
        q.y=700;
        q.h=50;
        q.w=50;

        SDL_SetRenderDrawColor(r,0,0,0,255);

        SDL_RenderFillRect(r,&q);

        SDL_RenderPresent(r);
    }

    SDL_DestroyWindow(o);
    SDL_DestroyRenderer(r);
    SDL_Quit();

    return 0;
}

1 个答案:

答案 0 :(得分:2)

您没有初始化矩形对象:

byte

之前可能在事件循环中修改其值,这将导致未定义的行为:

SDL_Rect q;

然后,当您为其设置常量值时,对该对象所做的任何更改都将失效:

case SDLK_UP:
    q.y -=10;
break;

因此解决方案很明确,只有在定义对象时才将常量值设置为对象。