Question

我正在使用SDL库来创建乒乓球游戏。我正要在键盘上按字母w时桨向上和向下移动的位置。我试图在按下w时移动矩形。但它行不通。以前可以使用，但是它只是在渲染器上进行绘画，而不是移动整个矩形。

 #include <iostream>
#include<SDL.h>
#include<fstream>
using namespace std;

SDL_Window *window = NULL;
SDL_Surface *screen = NULL;
Uint32 white;
Uint32 black;
SDL_Renderer *renderer;
const int HEIGHT = 700;
const int WIDTH = 800;
const int padH = 95;
const int padW = 25;
SDL_Event e;
SDL_Rect player;
SDL_Rect player2;
SDL_Rect Ball;
void init() 
{
    SDL_Init(SDL_INIT_EVERYTHING);
    window = SDL_CreateWindow("Pong",SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,WIDTH,HEIGHT,SDL_WINDOW_SHOWN);
    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
    screen = SDL_GetWindowSurface(window);
    white = SDL_MapRGB(screen->format, 255, 255, 255);
    black= SDL_MapRGB(screen->format, 0,0,0);
    player.h = padH;
    player.w = padW;
    player2.h = padH;
    player2.w = padW;

    player.x = 20;
    player.y = HEIGHT / 2;
    player2.x = WIDTH-40;
    player2.y = HEIGHT / 2;
    Ball.h = 20;
    Ball.w = 20;
    Ball.x = WIDTH / 2;
    Ball.y = HEIGHT / 2;


}

void draw() 
{
    SDL_SetRenderDrawColor(renderer,0,0,0,255);
    SDL_RenderClear(renderer);

    SDL_SetRenderDrawColor(renderer,255,255,255,255);
    SDL_RenderFillRect(renderer, &Ball);

    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
    SDL_RenderFillRect(renderer, &player);

    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
    SDL_RenderFillRect(renderer, &player2);

    SDL_RenderPresent(renderer);


}

void gamelogic()
{
    while (SDL_PollEvent(&e) !=0) 

    {
        if (e.type = SDL_KEYDOWN)
        {
            switch (e.key.keysym.sym)
            {
            case SDLK_w:
                SDL_RenderFillRect(renderer, &player);
                player.y = player.y + 1;

            }

        }

    }
}
int main(int arg, char*argv[]) {
    bool done = true;

    init();
    draw();
    gamelogic();
    while (done) 
    {
        SDL_PollEvent(&e);
        if (e.type == SDL_QUIT)
        {
            done = false;
        }

    }

    return 0;
}

当我在while循环中按下按键时，它只是保持绘画而不是移动矩形并将其刷过

Answer 1

您的主循环基本上是不存在的-它只会泵出事件队列并在最后一个窗口关闭时退出（或在此之前的任何时间，因为您从不检查是否有事件但仍会对其进行反应-可能是任何事情）。主循环应在每次迭代中检查事件，对事件做出反应并重绘。您不需要在事件处理代码中绘制任何内容，并且if (e.type = SDL_KEYDOWN)是分配的，而不是比较的-我建议启用编译器警告。

总结起来，完整的例子（还有很大的改进余地）：

#include <iostream>
#include <SDL.h>
#include <fstream>
using namespace std;

SDL_Window *window = NULL;
SDL_Surface *screen = NULL;
Uint32 white;
Uint32 black;
SDL_Renderer *renderer;
const int HEIGHT = 700;
const int WIDTH = 800;
const int padH = 95;
const int padW = 25;
SDL_Event e;
SDL_Rect player;
SDL_Rect player2;
SDL_Rect Ball;
bool done = false;

void init() 
{
    SDL_Init(SDL_INIT_EVERYTHING);
    window = SDL_CreateWindow("Pong",SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,WIDTH,HEIGHT,SDL_WINDOW_SHOWN);
    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
    screen = SDL_GetWindowSurface(window);
    white = SDL_MapRGB(screen->format, 255, 255, 255);
    black= SDL_MapRGB(screen->format, 0,0,0);
    player.h = padH;
    player.w = padW;
    player2.h = padH;
    player2.w = padW;

    player.x = 20;
    player.y = HEIGHT / 2;
    player2.x = WIDTH-40;
    player2.y = HEIGHT / 2;
    Ball.h = 20;
    Ball.w = 20;
    Ball.x = WIDTH / 2;
    Ball.y = HEIGHT / 2;
}

void draw() 
{
    SDL_SetRenderDrawColor(renderer,0,0,0,255);
    SDL_RenderClear(renderer);

    SDL_SetRenderDrawColor(renderer,255,255,255,255);
    SDL_RenderFillRect(renderer, &Ball);

    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
    SDL_RenderFillRect(renderer, &player);

    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
    SDL_RenderFillRect(renderer, &player2);

    SDL_RenderPresent(renderer);
}

void gamelogic()
{
    while (SDL_PollEvent(&e) !=0) 
    {
        if (e.type == SDL_KEYDOWN)
        {
            switch (e.key.keysym.sym)
            {
            case SDLK_w:
                player.y = player.y + 1;

            }
        }
        else if (e.type == SDL_QUIT)
        {
            done = true;
        }
    }
}

int main(int arg, char*argv[]) {
    init();

    while (!done)
    {
        gamelogic();
        draw();
    }

    return 0;
}

如何使用方法在sdl2中的按键上移动矩形

1 个答案: