Question

如何在MFC对话框中使用SDL2

Answer 1

方法/步骤
新建MFC应用程序，工程名称为MFCSDL

本例使用基于对话框的程序，注意勾选“基于对话框”

在MFCSDLDlg.h中添加SDL library 头文件和库文件应用，并定义所需变量。
#include "../SDL2-2.0.3/include/sdl.h"
#pragma comment(lib, "../SDL2-2.0.3/lib/x86/SDL2.lib")
#define WINDOW_W 640
#define WINDOW_H 480
#define NUM_SPRITES 100
#define MAX_SPEED 1
static SDL_Window* window;
static SDL_Renderer *renderer;
static SDL_Texture * sprite;
static int window_w, window_h;
static int sprite_w, sprite_h;
static SDL_Rect *positions, *velocities;
添加WM_KICKIDLE消息，该消息为微软保留消息，不公开，用它可以避免自己再重载实现消息循环。
具体过程如下:
1. 在 MFCSDLdlg.h文件加入
afx_msg LRESULT OnKickIdle(WPARAM wParam, LPARAM lParam);
2. 在MFCSDLDlg.cpp中加入消息映射
BEGIN_MESSAGE_MAP(CMFCSDLDlg, CDialogEx)
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_MESSAGE(WM_KICKIDLE,OnKickIdle)
ON_WM_CLOSE()
END_MESSAGE_MAP()
3.添加OnKickIdle消息实现。
LRESULT CMFCSDLDlg::OnKickIdle(WPARAM wParam, LPARAM lParam)
{

SDL_Event event;
int done = 0;
while (!done)
{
/* Check for events */
while (SDL_PollEvent(&event)) {
switch (event.type) {
case SDL_WINDOWEVENT:
switch (event.window.event) {
case SDL_WINDOWEVENT_EXPOSED:
SDL_SetRenderDrawColor(renderer, 0xA0, 0xA0, 0xA0, 0xFF);
SDL_RenderClear(renderer);
break;
}
break;
case SDL_QUIT:
done = 1;
break;
default:
break;
}
}
MoveSprites(renderer, sprite);
}

return 0; //一定要返回0
}
在OnInitDialog函数中加入初始化代码。

BOOL CMFCSDLDlg::OnInitDialog()
{
CDialogEx::OnInitDialog();

// 设定此对话方块的图示。当应用程式的主视窗不是对话方块时，
// 框架会自动从事此作业
SetIcon(m_hIcon, TRUE); // 设定大图示
SetIcon(m_hIcon, FALSE); // 设定小图示

// TODO: 在此加入额外的初始设定
window = SDL_CreateWindowFrom(m_hWnd);
SDL_SetWindowTitle(window, "SDL Native Window Test");
renderer = SDL_CreateRenderer(window, -1, 0);
SDL_SetRenderDrawColor(renderer, 0xA0, 0xA0, 0xA0, 0xFF);
SDL_RenderClear(renderer);
sprite = LoadSprite(renderer, "icon.bmp");

SDL_GetWindowSize(window, &window_w, &window_h);
SDL_QueryTexture(sprite, NULL, NULL, &sprite_w, &sprite_h);
positions = (SDL_Rect *) SDL_malloc(NUM_SPRITES * sizeof(SDL_Rect));
velocities = (SDL_Rect *) SDL_malloc(NUM_SPRITES * sizeof(SDL_Rect));
if (!positions || !velocities) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Out of memory!\n");
// quit(2);
}
srand(time(NULL));
for (int i = 0; i < NUM_SPRITES; ++i) {
positions[i].x = rand() % (window_w - sprite_w);
positions[i].y = rand() % (window_h - sprite_h);
positions[i].w = sprite_w;
positions[i].h = sprite_h;
velocities[i].x = 0;
velocities[i].y = 0;
while (!velocities[i].x && !velocities[i].y) {
velocities[i].x = (rand() % (MAX_SPEED * 2 + 1)) - MAX_SPEED;
velocities[i].y = (rand() % (MAX_SPEED * 2 + 1)) - MAX_SPEED;
}
}
return TRUE; // 传回 TRUE，除非您对控制项设定焦点
}
在MFCSDLDlg.cpp中，添加LoadSprite函数，注意是static 全局函数，放在所有函数最上方。其作用是加载一个图片精灵，本例使用一个笑脸图片。
static SDL_Texture *
LoadSprite(SDL_Renderer *renderer, char *file)
{
SDL_Surface *temp;
SDL_Texture *sprite;

/* Load the sprite image */
temp = SDL_LoadBMP(file);
if (temp == NULL) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't load %s: %s", file, SDL_GetError());
return 0;
}

/* Set transparent pixel as the pixel at (0,0) */
if (temp->format->palette) {
SDL_SetColorKey(temp, 1, *(Uint8 *) temp->pixels);
}

/* Create textures from the image */
sprite = SDL_CreateTextureFromSurface(renderer, temp);
if (!sprite) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create texture: %s\n", SDL_GetError());
SDL_FreeSurface(temp);
return 0;
}
SDL_FreeSurface(temp);

/* We're ready to roll. :) */
return sprite;
}
在LoadSprite后添加MoveSprites函数，其作用是将精灵循环移动，实现动态效果。
static void
MoveSprites(SDL_Renderer * renderer, SDL_Texture * sprite)
{
if(renderer==NULL||sprite==NULL)
return;
int sprite_w, sprite_h;
int i;
SDL_Rect viewport;
SDL_Rect *position, *velocity;

/* Query the sizes */
SDL_RenderGetViewport(renderer, &viewport);
SDL_QueryTexture(sprite, NULL, NULL, &sprite_w, &sprite_h);

/* Draw a gray background */
SDL_SetRenderDrawColor(renderer, 0xA0, 0xA0, 0xA0, 0xFF);
SDL_RenderClear(renderer);

/* Move the sprite, bounce at the wall, and draw */
for (i = 0; i < NUM_SPRITES; ++i) {
position = &positions[i];
velocity = &velocities[i];
position->x += velocity->x;
if ((position->x < 0) || (position->x >= (viewport.w - sprite_w))) {
velocity->x = -velocity->x;
position->x += velocity->x;
}
position->y += velocity->y;
if ((position->y < 0) || (position->y >= (viewport.h - sprite_h))) {
velocity->y = -velocity->y;
position->y += velocity->y;
}

/* Blit the sprite onto the screen */
SDL_RenderCopy(renderer, sprite, NULL, position);
}

/* Update the screen! */
SDL_RenderPresent(renderer);
}
8
以上完成，按F7编译，将icon.bmp文件拷贝到程序执行文件加下，运行程序，可看到如图效果。

Answer 2

MFC中建立两个对话框，想要在第一个中如何调用第二个类的函数就需要把第二个类在第一个类中实例化作为第一个类中的一个成员变量，这样第一个类就能通过第二个类的这个实例，调用第二个类的函数。假设两个类分别为A、B，则关系就可以简洁举例如下：
class A{
private:
int c;
int d;
A()
{
c=5;
d=6;
}
public:
int funcplus()
{
return c+d;
}
}
class B{
public:
A a;
int b;
}
void main()
{
B b1;
int aaa = b1.funcplus();
}
则aaa的值为11 。