如何启用SDL2以允许所有key_down事件而不仅仅是退出事件？

Question

我的SDL窗口在另一个位图的顶部显示一个位图，但是我无法使用SDL_KeyDown事件来控制位图图像。 唯一有效的事件是SDL_QUIT。

我尝试使用ASWD键和上下左右箭头键进行映射，但是SDL窗口不处理任何这些事件。 发生的唯一事件是当我单击X按钮关闭窗口时，或者当我按q或Escape键关闭窗口时。 另外，控制台上没有出现任何printf语句，所以我不确定问题出在哪里，因为程序可以编译并运行而没有任何错误。

我正在使用C而不是C ++

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_timer.h>
#include <SDL_image.h>


#define WINDOW_WIDTH (640)
#define WINDOW_HEIGHT (480)
// Speed in Pixels/Seconds
#define SCROLL_SPEED (300)

// Spirte Size
#define SPRITE_SIZE    32


int main(int argc, const char * argv[]) {

// Attempt to initialize graphics library
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
    SDL_Log("Unable to initialize SDL: %s", SDL_GetError());
    return 1;
}

//Initialize Key Variables
SDL_Window *window = NULL;
SDL_Renderer *renderer = NULL;
SDL_Surface *windowSurface = NULL;
SDL_Surface *imageSurface = NULL;



// Creating Surfaces and Addresses
SDL_Surface *temp = NULL;
SDL_Surface *sprite = NULL;

// set sprite position
SDL_Rect dstSprite = {0, 0, 32, 32};


// Attempt to create SDL Window
window = SDL_CreateWindow("Atari Lunar Lander", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, WINDOW_WIDTH, WINDOW_HEIGHT, 0);

// Print an Error if the window fails to initialize
if (window == NULL) {
    printf("Could not create window: %s\n", SDL_GetError());
    return 1;
}

// Create The Title of the Window
SDL_SetWindowTitle(window, "Atari Lunar Lander");

// Create SDL Render Window
Uint32 render_flags = SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE;
renderer = SDL_CreateRenderer(window, -1, render_flags);

// if rendering the window fails
if (!renderer) {
    printf("error creating render: %s\n", SDL_GetError());
    SDL_DestroyWindow(window);
    SDL_Quit();
    return 1;
}

windowSurface = SDL_GetWindowSurface(window);

// Load A bitmap image as an Surface
windowSurface = SDL_LoadBMP("/Users/jeremiahonwubuya/Desktop/AtariLunarLander/outerspace.bmp");

if (!windowSurface) {
    printf("error creating surface: %s\n", SDL_GetError());
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
    return 1;
}

//Load Image data into graphics hardware memory
SDL_Texture *texture = SDL_CreateTextureFromSurface(renderer, windowSurface);


if (!texture) {
    printf("error creating texture: %s\n", SDL_GetError());
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
    return 1;
}


// load bitmap image into an SDL_Surface "temp" and store "temp" into the SDL_Surface "sprite" that is optimized for Blitting
temp   = SDL_LoadBMP("/Users/jeremiahonwubuya/Desktop/AtariLunarLander/player.bmp");
sprite = SDL_ConvertSurface(temp, temp->format, 0);
SDL_FreeSurface(temp);

SDL_Texture *playerTexture = SDL_CreateTextureFromSurface(renderer, sprite);


if (!sprite) {
    printf("error creating sprite: %s\n", SDL_GetError());
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
    return 1;
}



// updating the Window Surface to be the BitMap Image
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture, NULL, NULL);
SDL_RenderCopy(renderer, playerTexture, NULL, &dstSprite);
SDL_RenderPresent(renderer);



bool isRunning = true;
SDL_Event event;

while (isRunning) {

    while (SDL_PollEvent(&event) != 0 ) {
        if (event.type == SDL_QUIT) {
            // close button clicked
            isRunning = false;
            break;
        }

        if (event.type == SDL_KEYDOWN) {
            // close program upon buttons pressed
            switch(event.key.keysym.sym){
                case SDLK_q:
                    printf("program stopped");
                    isRunning = false;
                    break;
                case SDLK_ESCAPE:
                    printf("programm stopped");
                    isRunning = false;
                    break;

            }

            // Animating the Sprite

            if (event.key.keysym.sym == SDLK_a || event.key.keysym.sym == SDLK_LEFT) {
                dstSprite.x -= 5;
                dstSprite.w = 32;
                dstSprite.h = 32;
                SDL_RenderClear(renderer);
                SDL_RenderCopy(renderer, texture, NULL, NULL);
                SDL_RenderCopy(renderer, playerTexture, NULL, &dstSprite);
                SDL_RenderPresent(renderer);
                printf("sprite moved leftt to position %d \n", dstSprite.x);

     }

            if (event.key.keysym.sym == SDLK_d || event.key.keysym.sym == SDLK_RIGHT) {
                dstSprite.x += 5;
                dstSprite.w = 32;
                dstSprite.h = 32;
                SDL_RenderClear(renderer);
                SDL_RenderCopy(renderer, texture, NULL, NULL);
                SDL_RenderCopy(renderer, playerTexture, NULL, &dstSprite);
                SDL_RenderPresent(renderer);
                printf("sprite moved right to position %d \n", dstSprite.x);

            }

            if (event.key.keysym.sym == SDLK_w || event.key.keysym.sym == SDLK_UP) {
                dstSprite.y -= 5;
                dstSprite.w = 32;
                dstSprite.h = 32;
                SDL_RenderClear(renderer);
                SDL_RenderCopy(renderer, texture, NULL, NULL);
                SDL_RenderCopy(renderer, playerTexture, NULL, &dstSprite);
                SDL_RenderPresent(renderer);
                printf("sprite moved up to position %d \n", dstSprite.y);


            }

            if (event.key.keysym.sym == SDLK_s || event.key.keysym.sym == SDLK_DOWN) {
                dstSprite.y += 5;
                dstSprite.w = 32;
                dstSprite.h = 32;
                SDL_RenderClear(renderer);
                SDL_RenderCopy(renderer, texture, NULL, NULL);
                SDL_RenderCopy(renderer, playerTexture, NULL, &dstSprite);
                SDL_RenderPresent(renderer);
                printf("sprite moved down to position %d \n", dstSprite.y);


            }

        }


      // Prevent Sprite from colliding with the edges of the screen

        if ( dstSprite.x < 0 ) {
            dstSprite.x = 0;
        }
        else if ( dstSprite.x > WINDOW_WIDTH-SPRITE_SIZE ) {
            dstSprite.x = WINDOW_WIDTH-SPRITE_SIZE;
        }
        if ( dstSprite.y < 0 ) {
            dstSprite.y = 0;
        }
        else if ( dstSprite.y > WINDOW_HEIGHT-SPRITE_SIZE ) {
            dstSprite.y = WINDOW_HEIGHT-SPRITE_SIZE;
        }


        // Draw the Sprite
        SDL_BlitSurface(sprite, NULL, windowSurface, &dstSprite);


        SDL_UpdateWindowSurface(window);
    }

}


SDL_Delay(5000);

// Clean Up

// Free SDL Surfaces
SDL_FreeSurface(sprite);
sprite = NULL;
SDL_FreeSurface(windowSurface);
windowSurface = NULL;
SDL_FreeSurface(imageSurface);
imageSurface = NULL;
// Destroy Texture and Window
texture = NULL;
SDL_DestroyTexture(texture);
playerTexture = NULL;
SDL_DestroyTexture(playerTexture);
window = NULL;
SDL_DestroyWindow(window);
SDL_Quit();

}

Answer 1

您的个案的OR'ing结果产生的整数与.sym中的整数不同。 您应该拆分OR，让它们失败或使用if条件。 例如：

case SDLK_a:    
case SDLK_LEFT: 
   printf("sprite moved leftt");
   break;

case SDLK_d:
case SDLK_RIGHT:
  printf("sprite moved right");
  break;

case SDLK_w:
case SDLK_UP:
  printf("sprite moved up");
  break;

case SDLK_s:
case SDLK_DOWN:
  printf("sprite moved down");
  break;

要么

if (event.key.keysym.sym == SDLK_a || event.key.keysym.sym == SDLK_LEFT)
  // do something..

所以，首先，您的代码正在“工作”，当我按正确的键时，我将文本打印出来，但是您还有另一个错误，ifs中的中断使您跳过了bliting部分，请记住，中断会中断执行在switch，for和while循环中流动，在ifs上不需要它们。

另外，如果您按某个键，然后不按任何键，则应该更新屏幕。 我对此程序进行了测试。 告诉我它是否正在接收您的钥匙。

#include <SDL2/SDL.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
    SDL_Init(SDL_INIT_VIDEO);

    bool isRunning = true;
    SDL_Event event;
    SDL_Rect dstSprite = {0, 0, 0, 0};
    while (isRunning) {

        while (SDL_PollEvent(&event) != 0) {
            if (event.type == SDL_QUIT) {
                // close button clicked
                isRunning = false;
                break;
            }

            if (event.type == SDL_KEYDOWN) {
                // close program upon buttons pressed
                switch (event.key.keysym.sym) {
                case SDLK_q:
                    printf("program stopped");
                    isRunning = false;
                    break;
                case SDLK_ESCAPE:
                    printf("programm stopped");
                    isRunning = false;
                    break;
                }

                // Animating the Sprite

                if (event.key.keysym.sym == SDLK_a ||
                    event.key.keysym.sym == SDLK_LEFT) {
                    dstSprite.x -= 5;
                    printf("sprite moved leftt to position %d \n", dstSprite.x);
                    break;
                }

                if (event.key.keysym.sym == SDLK_d ||
                    event.key.keysym.sym == SDLK_RIGHT) {
                    dstSprite.x += 5;
                    printf("sprite moved right to position %d \n", dstSprite.x);
                    break;
                }

                if (event.key.keysym.sym == SDLK_w ||
                    event.key.keysym.sym == SDLK_UP) {
                    dstSprite.y -= 5;
                    printf("sprite moved up to position %d \n", dstSprite.y);
                    break;
                }

                if (event.key.keysym.sym == SDLK_s ||
                    event.key.keysym.sym == SDLK_DOWN) {
                    dstSprite.y += 5;
                    printf("sprite moved down to position %d \n", dstSprite.y);
                    break;
                }
            }
            printf("update graphics\n");
        }
    }
}