C++ SDL2事件处理 C++ SDL2事件处理

配置请参照前面的笔记https://www.cnblogs.com/zzr-stdio/p/14514043.html

这里主要介绍SDL_PollEvent函数，以及SDL_Event的结构数据

示例程序：

#include <iostream>
#include<SDL.h>
#include<SDL_image.h>
using namespace std;
int main(int argc, char* argv[])
{
    ::SDL_Init(SDL_INIT_VIDEO);//初始化SDL
    ::SDL_Window* window = ::SDL_CreateWindow("SDL test", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
        800, 600, SDL_WINDOW_SHOWN);//创建窗体
    ::SDL_Surface* surface = ::SDL_GetWindowSurface(window);//得到窗体的SDL_Surface
    //::SDL_Surface* image = ::SDL_LoadBMP("r.bmp");//加载图片
    ::SDL_Surface* image = ::IMG_Load("2.png");//加载png图片
    ::SDL_Rect rect;
    rect.x = 100;//显示位置
    rect.y = 0;
    bool quit = false;
    ::SDL_Event event;
    while (quit == false)
    {
        while (::SDL_PollEvent(&event))//对当前待处理事件进行轮询
        {
            if (event.type == ::SDL_QUIT)//退出事件
            {
                quit = true;
            }
            else if (event.type == SDL_MOUSEBUTTONDOWN) //鼠标按下事件
            {
                if (event.button.button == SDL_BUTTON_LEFT)//判断是鼠标左键
                {
                    cout << "左" << endl;
                }
                else if (event.button.button == SDL_BUTTON_RIGHT)//判断是鼠标右键
                {
                    cout << "右" << endl;
                }
            }
            else if (event.type == SDL_KEYDOWN)//键盘事件
            {
                cout << (char)event.key.keysym.sym << endl;//输出键盘字符
            }
            else if(event.type == SDL_DROPFILE)//文件拖动事件
            {
                image = ::IMG_Load(event.drop.file);
                cout << event.drop.file << endl;
            }
        }
        ::SDL_FillRect(surface, nullptr, 0);
        ::SDL_BlitSurface(image, nullptr, surface, &rect);//把图片贴到窗体上
        ::SDL_UpdateWindowSurface(window);//刷新窗口，不调用则显示不了图片。
    }
    
    ::SDL_DestroyWindow(window);//销毁窗体
    ::SDL_Quit();//退出SDL
    return 0;
}

SDL_Event的定义为：

typedef union SDL_Event
{
    Uint32 type;                            //事件类型
    SDL_CommonEvent common;                 /**< Common event data */
    SDL_DisplayEvent display;               /**< Display event data */
    SDL_WindowEvent window;                 /**< Window event data */
    SDL_KeyboardEvent key;                  //键盘事件，键盘按下和释放
    SDL_TextEditingEvent edit;              /**< Text editing event data */
    SDL_TextInputEvent text;                /**< Text input event data */
    SDL_MouseMotionEvent motion;            //鼠标移动事件
    SDL_MouseButtonEvent button;            //鼠标按键事件
    SDL_MouseWheelEvent wheel;              /**< Mouse wheel event data */
    SDL_JoyAxisEvent jaxis;                 /**< Joystick axis event data */
    SDL_JoyBallEvent jball;                 /**< Joystick ball event data */
    SDL_JoyHatEvent jhat;                   /**< Joystick hat event data */
    SDL_JoyButtonEvent jbutton;             /**< Joystick button event data */
    SDL_JoyDeviceEvent jdevice;             /**< Joystick device change event data */
    SDL_ControllerAxisEvent caxis;          /**< Game Controller axis event data */
    SDL_ControllerButtonEvent cbutton;      /**< Game Controller button event data */
    SDL_ControllerDeviceEvent cdevice;      /**< Game Controller device event data */
    SDL_ControllerTouchpadEvent ctouchpad;  /**< Game Controller touchpad event data */
    SDL_ControllerSensorEvent csensor;      /**< Game Controller sensor event data */
    SDL_AudioDeviceEvent adevice;           /**< Audio device event data */
    SDL_SensorEvent sensor;                 /**< Sensor event data */
    SDL_QuitEvent quit;                     //退出事件
    SDL_UserEvent user;                     //用户自定义事件
    SDL_SysWMEvent syswm;                   //平台相关的系统事件
    SDL_TouchFingerEvent tfinger;           /**< Touch finger event data */
    SDL_MultiGestureEvent mgesture;         /**< Gesture event data */
    SDL_DollarGestureEvent dgesture;        /**< Gesture event data */
    SDL_DropEvent drop;                     //拖拽事件

    /* This is necessary for ABI compatibility between Visual C++ and GCC
       Visual C++ will respect the push pack pragma and use 52 bytes for
       this structure, and GCC will use the alignment of the largest datatype
       within the union, which is 8 bytes.

       So... we'll add padding to force the size to be 56 bytes for both.
    */
    Uint8 padding[56];
} SDL_Event;