c++ - SDL 如何在按下键时为 Sprite 设置动画

Question

我要开门见山了:我有一个有 8 个运动 Sprite 的 Sprite 表(http://i.imgur.com/hLpo2Qn.png 不能发布图像:\)，所以它创造了我走路的错觉)我的问题是，当我按住一个键时，我希望 Sprite 有点像动画行走。例如，当我按下向上箭头时，前两个 Sprite 会循环播放，直到我松开按键。到目前为止，我所能做的就是在每个方向上只显示一个 Sprite ，所以它会产生一种不切实际的效果。代码:

#include <SDL/SDL.h>

int main(int argc, char* argv[])
{
SDL_Init(SDL_INIT_EVERYTHING);
SDL_Surface* screen, *image;
screen = SDL_SetVideoMode(640, 480, 32, SDL_SWSURFACE);
bool running = true;
const int FPS = 30;
Uint32 start;
bool direction[4] = {0, 0, 0, 0};
SDL_Rect pos;
    pos.x = 0;
    pos.y = 0;
    SDL_Rect sprite;
    sprite.x = 160;
    sprite.y = 0;
    sprite.w = 32;
    sprite.h = 32;;
Uint32 color = SDL_MapRGB(screen -> format, 0xff, 0xff, 0xff);
image = SDL_DisplayFormat(SDL_LoadBMP("sprite.bmp"));
SDL_SetColorKey(image, SDL_SRCCOLORKEY, SDL_MapRGB(screen -> format, 255, 0, 255));
while (running == true)
{
    start = SDL_GetTicks();
    SDL_Event event;
    while(SDL_PollEvent(&event))
    {
        switch(event.type)
        {
        case SDL_QUIT:
            running = false;
            break;
        case SDL_KEYDOWN:
            switch(event.key.keysym.sym)
            {
            case SDLK_UP:
                direction[0] = 1;
                sprite.x = 0;
                break;
            case SDLK_LEFT:
                direction[1] = 1;
                sprite.x = 224;
                break;
            case SDLK_DOWN:
                direction[2] = 1;
                sprite.x = 160;
                break;
            case SDLK_RIGHT:
                direction[3] = 1;
                sprite.x = 96;
                break;
            }
            break;
        case SDL_KEYUP:
            switch(event.key.keysym.sym)
            {
            case SDLK_UP:
                direction[0] = 0;
                sprite.x = 32;
                break;
            case SDLK_LEFT:
                direction[1] = 0;
                break;
            case SDLK_DOWN:
                direction[2] = 0;
                break;
            case SDLK_RIGHT:
                direction[3] = 0;
                break;
            }
            break;
        }
    }
    if(direction[0])
        pos.y-- ;
    if(direction[1])
        pos.x--;
    if(direction[2])
        pos.y++;
    if(direction[3])
        pos.x++;

    SDL_FillRect(screen, &screen -> clip_rect, color);
    SDL_BlitSurface(image, &sprite, screen, &pos);
    SDL_Flip(screen);

        if(1000 / FPS > SDL_GetTicks() - start)
        SDL_Delay(1000 / FPS - (SDL_GetTicks() - start));

}
SDL_FreeSurface(image);
SDL_Quit();
return 0;

Answer 1

免责声明:这不是实现您想要的唯一或最佳方法。这只是一种可能的解决方案

您需要实现一个基本的计时器/计数器以在两个适当的图像之间切换。

对于这个例子，我会将您的 Sprite 偏移量存储在二维数组 int sprite_x[4][2]; - 这将代表四个方向和每个方向的两个图像偏移量。然后在按键上而不是使用 bool 数组只有一个整数索引 int sprite_index; 用于索引 sprite 偏移量。然后你需要做的就是有另一个整数值，类似于 int current_key;，你可以在 0 和 1 之间切换。

// Used for indexing the 2D array
enum
{
    WALK_LEFT,
    WALK_RIGHT,
    WALK_UP,
    WALK_DOWN

    WALK_MAX
};

// How many sprites per animation
const int NUM_KEYFRAMES = 2;

// 2D array to hold the x value offsets for sprites
int sprite_x[WALK_MAX][NUM_KEYFRAMES];

int sprite_index = WALK_LEFT;  // Current animation
int current_key = 0;           // Current keyframe for the animation

// Set up all the x value offsets in the array
sprite_x[WALK_LEFT][0] = 0;
sprite_x[WALK_LEFT][1] = 32;
sprite_x[WALK_RIGHT][0] = 64;
sprite_x[WALK_RIGHT][1] = 96;
.
.
.

然后您只需相应地更新 Sprite x 值 sprite.x = sprite_x[sprite_index][current_key];