作者：龙飞
3.1：一些小的修改
我觉得写C++的程序，一是看起来确实比较C++一点，二是相对于C的“精炼”，C++要的是“健壮”。所以，其实我不太满意用C风格字符串作为ScreenSurface的成员数据，所以做了修改。这也是为了在程序中构建ScreenSurface对象的时候可以使用string。
class ScreenSurface
{
private:
//
std::string windowName;
public:
//
ScreenSurface(int w, int h, const std::string& window_name = "NULL", int b = 0, Uint32 f = 0);
};
相应的，我们修改了2个构造函数。
ScreenSurface::ScreenSurface():
width(640), height(480), bpp(32), flags(0), windowName("NULL")
{
if ( screenNum > 0 )
throw ErrorInfo("DONOT create more than ONE screen!");
if ( SDL_Init(SDL_INIT_VIDEO < 0 ) )
throw ErrorInfo(SDL_GetError());
pScreen = SDL_SetVideoMode(width, height, bpp, flags);
screenNum++;
}
ScreenSurface::ScreenSurface(int w, int h, const std::string& window_name, int b, Uint32 f):
width(w), height(h), bpp(b), flags(f)
{
if ( screenNum > 0 )
throw ErrorInfo("DONOT create more than ONE screen!");
if ( SDL_Init(SDL_INIT_VIDEO < 0 ) )
throw ErrorInfo(SDL_GetError());
pScreen = SDL_SetVideoMode(width, height, bpp, flags);
screenNum++;
if ( window_name != "NULL" ) {
windowName = window_name;
SDL_WM_SetCaption(windowName.c_str(), 0);
}
else
windowName = "NULL";
}
第二个地方，我修改了TextSurface构造函数的参数顺序，并且将默认的字体改为Windows都自带的“新罗马时代”字体times.ttf。我将字体参数放在最后，将字体大小参数提前了，这样更符合习惯上的使用规律。
class TextSurface: public DisplaySurface
{
public:
TextSurface(const std::string& msg_name, const std::string& message, const ScreenSurface& screen,
Uint8 r = 0xFF, Uint8 g = 0xFF, Uint8 b = 0xFF,
int ttf_size = 28, const std::string& ttf_fileName = "times.ttf");
~TextSurface();
};
（在DisplaySurface里相应的构造函数也做类似的修改，略）
3.2：回顾SDL事件轮询
SDL_PollEvent()的作用，是事件一旦被触发，就会响应一次，注意它的响应并不是连续不断的。比如你按下某个键，即触发了一次事件。即使你按着不松开，也仅仅是触发了一次，所以SDL_PollEvent()也只响应一次。
下面的程序，演示键盘事件中，方向键被按下后的反馈信息。
3.3：演示程序
//UVi Soft (2008)
//Long Fei (lf426), E-mail: zbln426@163.com
#include "SurfaceClass.h"
int game(int argc, char* argv[]);
int main(int argc ,char* argv[])
{
int mainRtn = 0;
try {
mainRtn = game(argc, argv);
}
catch ( const ErrorInfo& info ) {
info.show();
return -1;
}
return mainRtn;
}
int game(int argc ,char* argv[])
{
//Create a SDL screen.
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const std::string WINDOW_NAME = "Key Presses";
ScreenSurface screen(SCREEN_WIDTH, SCREEN_HEIGHT, WINDOW_NAME);
//Fill background.(default is black)
screen.fillColor();
screen.flip();
//Load a textSurface
TextSurface upMessage("upMsg", "Up was pressed.", screen);
TextSurface downMessage("downMsg", "Down was pressed.", screen, 0xFF, 0, 0);
TextSurface leftMessage("leftMsg", "Left was pressed.", screen, 0, 0xFF, 0);
TextSurface rightMessage("rightMsg", "Right was pressed.", screen, 0, 0, 0xFF);
TextSurface otherMessage("otherMsg", "Other key was pressed.", screen, 100, 100, 100, 35);
//Main loop.Press ESC or click X to quit.
bool gameOver = false;
SDL_Event gameEvent;
int x = 200;
int y = 200;
while( gameOver == false ){
while ( SDL_PollEvent(&gameEvent) != 0 ){
if ( gameEvent.type == SDL_KEYDOWN ){
screen.fillColor();
switch ( gameEvent.key.keysym.sym ){
case SDLK_UP:
upMessage.blit(x, y--);
break;
case SDLK_DOWN:
downMessage.blit(x, y++);
break;
case SDLK_LEFT:
leftMessage.blit(x--, y);
break;
case SDLK_RIGHT:
rightMessage.blit(x++, y);
break;
default:
otherMessage.blit(x, y);
}
screen.flip();
}
if ( gameEvent.type == SDL_QUIT ){
gameOver = true;
}
if ( gameEvent.type == SDL_KEYUP ){
if ( gameEvent.key.keysym.sym == SDLK_ESCAPE ){
gameOver = true;
}
}
}
}
return 0;
}
posted on 2008-03-25 11:56
lf426 阅读(1827)
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