程序因删除 SDL_PollEvent 而崩溃

Question

为什么当我从 main 中删除 SDL_PollEvent 行时我的程序会崩溃？我想在不使用事件的情况下在我的游戏系统中保留输入管理 class。

我也试过将 !gamesystem.boot() 放在 while 语句本身中，但无济于事。

主要：

int main(int argc, char* args[])
{
    if(!init())
    {
        printf("Failed to initialize!\n");
    }
    else
    {
        GameSystem gamesystem;
        gamesystem.startup(gRenderer,gGameController1,gGameController2);
        bool quit = false;
        SDL_Event e;
        while(!quit)
        {
            while(SDL_PollEvent(&e)!=0)
            {
                if(e.type == SDL_QUIT)
                {
                    quit = true;
                }
            }
            if(!gamesystem.boot())
                quit = true;
        }
    }
    close();
    return 0;
}

游戏系统：

#include "GameSystem.h"

GameSystem::GameSystem()
{
}

void GameSystem::startup(SDL_Renderer* gRenderer, SDL_Joystick* gGameController1, SDL_Joystick* gGameController2)
{
    gameRenderer = gRenderer;
    controller1 = gGameController1;
    controller2 = gGameController2;
    title.loadFile(gameRenderer, "Art/Title.png");
    arrow.loadFile(gameRenderer, "Art/Arrow.png");
    beep = Mix_LoadWAV("SFX/Beep.wav");
    boop = Mix_LoadWAV("SFX/Boop.wav");
    buup = Mix_LoadWAV("SFX/Buup.wav");
    baap = Mix_LoadWAV("SFX/Baap.wav");
}

bool GameSystem::boot()
{
    renderClear();
    if(menu == 0)
    {
        title.render(gameRenderer, 0,0);
        if(selection == 0)
            arrow.render(gameRenderer, 215, 400);
        else if(selection == 1)
            arrow.render(gameRenderer, 250, 440);
        else if(selection == 2)
            arrow.render(gameRenderer, 235, 482);
        else if(selection == 3)
            arrow.render(gameRenderer, 255, 528);
    }
    update();
    return quit;
}

enum buttons GameSystem::controls()
{
    const Uint8 *state = SDL_GetKeyboardState(NULL);
    if(state [SDL_SCANCODE_DOWN] || SDL_JoystickGetHat(controller1, 0) == SDL_HAT_DOWN)
        return u;
    else if(state [SDL_SCANCODE_UP] || SDL_JoystickGetHat(controller1, 0) == SDL_HAT_UP)
        return d;
    else if(state [SDL_SCANCODE_LEFT] || SDL_JoystickGetHat(controller1, 0) == SDL_HAT_LEFT)
        return l;
    else if(state [SDL_SCANCODE_RIGHT] || SDL_JoystickGetHat(controller1, 0) == SDL_HAT_RIGHT)
        return r;
    else if(state [SDL_SCANCODE_X] || SDL_JoystickGetButton(controller1, 0))
        return a;
    else if(state [SDL_SCANCODE_C] || SDL_JoystickGetButton(controller1, 1))
        return b;
    else if(state [SDL_SCANCODE_S] || SDL_JoystickGetButton(controller1, 2))
        return x;
    else if(state [SDL_SCANCODE_D] || SDL_JoystickGetButton(controller1, 3))
        return y;
    else if(state [SDL_SCANCODE_RETURN])
        return start;
    else if(state [SDL_SCANCODE_SPACE])
        return select;


    return nopress;
}
void GameSystem::renderClear()
{
    SDL_SetRenderDrawColor(gameRenderer, 0, 0, 0, 0xFF);
    SDL_RenderClear(gameRenderer);
}

void GameSystem::update()
{
    switch(controls())
    {
    case u:
        Mix_PlayChannel(-1,beep,0);
        selection++;
        if(selection > 3) selection = 0;
        break;
    case d:
        Mix_PlayChannel(-1,beep,0);
        selection--;
        if(selection < 0) selection = 3;
        break;
    case l:
        Mix_PlayChannel(-1,beep,0);
        break;
    case r:
        Mix_PlayChannel(-1,beep,0);
        break;
    case a:
        Mix_PlayChannel(-1,beep,0);
        if(selection == 3) quit = false;
        break;
    case b:
        Mix_PlayChannel(-1,boop,0);
        break;
    case x:
        Mix_PlayChannel(-1,buup,0);
        break;
    case y:
        Mix_PlayChannel(-1,baap,0);
        break;
    }
    //takes in vector of things to render after they have been sorted and renders them//

    //^render vector here^//
    SDL_RenderPresent(gameRenderer);
}

Answer 1

你的程序没有崩溃，它只是忽略了输入（它是 "not responding"）。它只会重复运行 gamesystem.boot() 而不会检测到您的输入。

实际上，SDL_PollEvent() internally calls SDL_PumpEvents() 更新输入。当您删除 SDL_PollEvent() 时，SDL 永远不会更新其内部输入设备状态，因此 SDL_GetKeyboardState() 始终 returns 其初始状态。

用 SDL_PumpEvents() 替换 PollEvent 循环应该可以解决这个问题。

程序因删除 SDL_PollEvent 而崩溃

Program crash with removal of SDL_PollEvent

c++

sdl-2