我正在使用各种在线教程和几本书自学编程。目前它是C++。在过去的几天里，我做了一些OpenGL和 SDL。
我有一个小程序可以创建一堵墙来阻止一个小方块穿过它。
这是我的代码：
//
// main.cpp
// SDL_Template
//
// The headers
#include <stdlib.h>
#include <string>
// SDL headers
#include <SDL/SDL.h>
#include "SDL_image/SDL_image.h"
//#include "SDL/SDL_ttf.h"
//#include "SDL/SDL_mixer.h"
// Other headers
#include <OpenGL/gl3.h>
// Screen attributes
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;
// The frame rate
const int FRAMES_PER_SECOND = 20;
// The attributes of the square
const int SQUARE_WIDTH = 20;
const int SQUARE_HEIGHT = 20;
// The surfaces
SDL_Surface *square = NULL;
SDL_Surface *screen = NULL;
// The event structure
SDL_Event event;
// The wall
SDL_Rect wall;
// The square
class Square
{
private:
// The collision box of the square
SDL_Rect box;
// The velocity of the square
int xVel, yVel;
public:
// Initializes the variables
Square();
// Takes key presses and adjusts the square's velocity
void handle_input();
// Moves the square
void move();
// Shows the square on the screen
void show();
};
//The timer
class Timer
{
private:
// The clock time when the timer started
int startTicks;
// The ticks stored when the timer was paused
int pausedTicks;
// The timer status
bool paused;
bool started;
public:
// Initializes variables
Timer();
// The various clock actions
void start();
void stop();
void pause();
void unpause();
// Gets the timer's time
int get_ticks();
// Checks the status of the timer
bool is_started();
bool is_paused();
};
SDL_Surface *load_image(std::string filename)
{
// The image that's loaded
SDL_Surface* loadedImage = NULL;
// The optimized surface that will be used
SDL_Surface* optimizedImage = NULL;
// Load the image
loadedImage = IMG_Load(filename.c_str());
// If the image loaded
if (loadedImage != NULL)
{
// Create an optimized surface
optimizedImage = SDL_DisplayFormat(loadedImage);
// Free the old surface
SDL_FreeSurface(loadedImage);
// If the surface was optimized
if (optimizedImage != NULL)
{
// Color key surface
SDL_SetColorKey(optimizedImage, SDL_SRCCOLORKEY, SDL_MapRGB(optimizedImage->format, 0, 0xFF, 0xFF));
}
}
// Return the optimized surface
return optimizedImage;
}
void apply_surface(int x, int y, SDL_Surface* source, SDL_Surface* destination, SDL_Rect* clip = NULL)
{
// Holds offsets
SDL_Rect offset;
// Get offsets
offset.x = x;
offset.y = y;
// Blit
SDL_BlitSurface(source, clip, destination, &offset);
}
bool check_collision(SDL_Rect A, SDL_Rect B)
{
// The sides of the rectangles
int leftA, leftB;
int rightA, rightB;
int topA, topB;
int bottomA, bottomB;
// Calculate the sides of rect A
leftA = A.x;
rightA = A.x + A.w;
topA = A.y;
bottomA = A.y + A.h;
// Calculate the sides of rect B
leftB = B.x;
rightB = B.x + B.w;
topB = B.y;
bottomB = B.y + B.h;
// If any of the sides from A are outside of B
if( bottomA <= topB )
{
return false;
}
if( topA >= bottomB )
{
return false;
}
if( rightA <= leftB )
{
return false;
}
if( leftA >= rightB )
{
return false;
}
// If none of the sides from A are outside B
return true;
}
bool init()
{
// Initialize all SDL subsystems
if (SDL_Init( SDL_INIT_EVERYTHING ) == -1)
{
return false;
}
// Set up the screen
screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);
// If there was an error in setting up the screen
if (screen == NULL)
{
return false;
}
// Set the window caption
SDL_WM_SetCaption("Move the Square", NULL);
// If everything initialized fine
return true;
}
bool load_files()
{
// Load the square image
square = load_image("square.bmp");
// If there was a problem in loading the square
if (square == NULL)
{
return false;
}
// If everything loaded fine
return true;
}
void clean_up()
{
// Free the surface
SDL_FreeSurface(square);
// Quit SDL
SDL_Quit();
}
Square::Square()
{
// Initialize the offsets
box.x = 0;
box.y = 0;
// Set the square's dimentions
box.w = SQUARE_WIDTH;
box.h = SQUARE_HEIGHT;
// Initialize the velocity
xVel = 0;
yVel = 0;
}
void Square::handle_input()
{
// If a key was pressed
if (event.type == SDL_KEYDOWN)
{
//Adjust the velocity
switch (event.key.keysym.sym)
{
case SDLK_UP: yVel -= SQUARE_HEIGHT / 2; break;
case SDLK_DOWN: yVel += SQUARE_HEIGHT / 2; break;
case SDLK_LEFT: xVel -= SQUARE_WIDTH / 2; break;
case SDLK_RIGHT: xVel += SQUARE_WIDTH / 2; break;
}
}
// If a key was released
else if (event.type == SDL_KEYUP)
{
//Adjust the velocity
switch (event.key.keysym.sym)
{
case SDLK_UP: yVel += SQUARE_HEIGHT / 2; break;
case SDLK_DOWN: yVel -= SQUARE_HEIGHT / 2; break;
case SDLK_LEFT: xVel += SQUARE_WIDTH / 2; break;
case SDLK_RIGHT: xVel -= SQUARE_WIDTH / 2; break;
}
}
}
void Square::move()
{
// Move the square left or right
box.x += xVel;
// If the square went too far to the left or right or has collided with the wall
if (( box.x < 0 ) || ( box.x + SQUARE_WIDTH > SCREEN_WIDTH ) || ( check_collision(box, wall)))
{
// Move back
box.x -= xVel;
}
// Move the square up or down
box.y += yVel;
// If the square went too far up or down or has collided with the wall
if (( box.y < 0 ) || ( box.y + SQUARE_HEIGHT > SCREEN_HEIGHT) || (check_collision(box, wall)))
{
// Move back
box.y -= yVel;
}
}
void Square::show()
{
// Show the square
apply_surface(box.x, box.y, square, screen);
}
Timer::Timer()
{
// Initialize the variables
startTicks = 0;
pausedTicks = 0;
paused = false;
started = false;
}
void Timer::start()
{
// Start the timer
started = true;
// Unpause the timer
paused = false;
// Get the current clock time
startTicks = SDL_GetTicks();
}
void Timer::stop()
{
// Stop the timer
started = false;
// Unpause the timer
paused = false;
}
void Timer::pause()
{
// If the timer is running and isn't already paused
if ((started == true) && (paused == false))
{
// Pause the timer
paused = true;
// Calculate the paused ticks
pausedTicks = SDL_GetTicks() - startTicks;
}
}
void Timer::unpause()
{
// If the timer is paused
if (paused == true)
{
// Unpause the timer
paused = false;
// Reset the starting ticks
startTicks = SDL_GetTicks() - pausedTicks;
// Reset the paused ticks
pausedTicks = 0;
}
}
int Timer::get_ticks()
{
// If the timer is running
if (started == true)
{
// If the timer is paused
if (paused == true)
{
// Return the number of ticks when the timer was paused
return pausedTicks;
}
else
{
// Return the current time minus the start time
return SDL_GetTicks() - startTicks;
}
}
// If the timer isn't running
return 0;
}
bool Timer::is_started()
{
return started;
}
bool Timer::is_paused()
{
return paused;
}
int main(int argc, char* args[])
{
// Quit flag
bool quit = false;
// The square
Square mySquare;
// The frame rate regulator
Timer fps;
// Initialize
if( init() == false )
{
return 1;
}
// Load the files
if (load_files() == false)
{
return 1;
}
// Set the wall
wall.x = 300;
wall.y = 40;
wall.w = 40;
wall.h = 400;
// While the user hasn't quit
while (quit == false)
{
// Start the frame timer
fps.start();
// While there are events to handle
while (SDL_PollEvent(&event))
{
// Handle events for the square
mySquare.handle_input();
// If the user has Xed out the window
if (event.type == SDL_QUIT)
{
// Quit the program
quit = true;
}
}
// Move the square
mySquare.move();
// Fill the screen white
SDL_FillRect(screen, &screen->clip_rect, SDL_MapRGB(screen->format, 0xFF, 0xFF, 0xFF));
// Show the wall
SDL_FillRect (screen, &wall, SDL_MapRGB(screen->format, 0x77, 0x77, 0x77));
// Show the square on the screen
mySquare.show();
// Update the screen
if (SDL_Flip(screen) == -1)
{
return 1;
}
// Cap the frame rate
if (fps.get_ticks() < 1000 / FRAMES_PER_SECOND)
{
SDL_Delay((1000 / FRAMES_PER_SECOND) - fps.get_ticks());
}
}
// Clean up
clean_up();
return 0;
}
我完全理解这个网站的工作原理，所以我不要求你检查我的代码。我的代码在 Xcode 4.5 和 Visual Studio 2010 中都可以编译。在 Xcode 中它可以编译，但会引发一些警告（尽管它仍然会构建），但在运行时没有任何反应。但是在 Visual Studio 2012 中，它可以编译，没有警告并且成功运行。
我已经搜索过这里和 C++/SDL 论坛/帮助页面，但我没有找到任何类似的案例。
为什么会这样？似乎它在 Visual Studio 2010 中运行，我相信它不是代码......
如果您想知道 Xcode 中标记的警告是：
229 枚举值未在开关中处理：'SDLK_UNKNOWN'、'SDLK_BACKSPACE'、'SDLK_TAB'...
这在switch (event.key.keysym.sym)代码行上突出显示。
所以我的问题是：
什么样的问题可能会导致此警告错误？
在 Visual Studio 而不是 Xcode 中运行的程序是否存在任何众所周知的问题？
我猜（似乎我找不到任何关于它的东西）这是一个我没有发现的地方......
我为这篇文章的长度道歉。