学步园

 对引擎作以下修改：

1.添加键盘支持

2.添加鼠标支持

3.修改Bitmap类,使其支持位图透明

4.添加错误退出代码

修改代码如下:

GameEngine.h

函数声明
//键盘函数
void HandleKeys();
//鼠标函数
void MouseButtonDown(int x, int y, BOOL bLeft);
void MouseButtonUp(int x, int y, BOOL bLeft);
void MouseMove(int x, int y);
//退出
void ErrorQuit(LPTSTR szErrorMsg);

GameEngine.cpp
        if (iTickCount > iTickTrigger)
          {
            iTickTrigger = iTickCount +
              GameEngine::GetEngine()->GetFrameDelay();
            HandleKeys();	//增加了这个函数
            GameCycle();
          }
    ...
    ...

    case WM_LBUTTONDOWN:
      // Handle left mouse button press
      MouseButtonDown(LOWORD(lParam), HIWORD(lParam), TRUE);
      return 0;

    case WM_LBUTTONUP:
      // Handle left mouse button release
      MouseButtonUp(LOWORD(lParam), HIWORD(lParam), TRUE);
      return 0;

    case WM_RBUTTONDOWN:
      // Handle right mouse button press
      MouseButtonDown(LOWORD(lParam), HIWORD(lParam), FALSE);
      return 0;

    case WM_RBUTTONUP:
      // Handle right mouse button release
      MouseButtonUp(LOWORD(lParam), HIWORD(lParam), FALSE);
      return 0;

    case WM_MOUSEMOVE:
      // Handle mouse movement
      MouseMove(LOWORD(lParam), HIWORD(lParam));
      return 0;

    ...
    ...

void GameEngine::ErrorQuit(LPTSTR szErrorMsg)
{
  MessageBox(GetWindow(), szErrorMsg, TEXT("Critical Error"), MB_OK | MB_ICONERROR);
  PostQuitMessage(0);
}

修改Bitmap.h
  void Draw(HDC hDC, int x, int y, BOOL bTrans = FALSE,
    COLORREF crTransColor = RGB(255, 0, 255));	//初始默认值为不透明,透明色为紫色

修改Bitmap.cpp的Draw()方法
void Bitmap::Draw(HDC hDC, int x, int y, BOOL bTrans, COLORREF crTransColor)
{
     ...
    if (bTrans)
      TransparentBlt(hDC, x, y, GetWidth(), GetHeight(), hMemDC, 0, 0,
        GetWidth(), GetHeight(), crTransColor);
    else
      BitBlt(hDC, x, y, GetWidth(), GetHeight(), hMemDC, 0, 0, SRCCOPY);
}

其中TransparentBlt()方法需要向项目添加msimg32.lib库
基于以上修改,一个UFO实例如下:
代码清单:
//-----------------------------------------------------------------
// UFO Application
// C++ Header - UFO.h
//-----------------------------------------------------------------

#pragma once

//-----------------------------------------------------------------
// Include Files
//-----------------------------------------------------------------
#include 
#include "Resource.h"
#include "GameEngine.h"
#include "Bitmap.h"

//-----------------------------------------------------------------
// Global Variables
//-----------------------------------------------------------------
HINSTANCE   g_hInstance;
GameEngine* g_pGame;
const int   g_iMAXSPEED = 8;	//最大速度
Bitmap*     g_pBackground;	//背景位图
Bitmap*     g_pSaucer;		//UFO位图
int         g_iSaucerX, g_iSaucerY;	//UFO的X/Y坐标
int         g_iSpeedX, g_iSpeedY;	//UFO的X/Y方向的速度
 
 

//-----------------------------------------------------------------
// UFO Application
// C++ Source - UFO.cpp
//-----------------------------------------------------------------

//-----------------------------------------------------------------
// Include Files
//-----------------------------------------------------------------
#include "UFO.h"

//-----------------------------------------------------------------
// Game Engine Functions
//-----------------------------------------------------------------
BOOL GameInitialize(HINSTANCE hInstance)
{
  // Create the game engine
  g_pGame = new GameEngine(hInstance, TEXT("UFO"),
    TEXT("UFO"), IDI_UFO, IDI_UFO_SM, 500, 400);
  if (g_pGame == NULL)
    return FALSE;
  
  // Set the frame rate
  g_pGame->SetFrameRate(30);

  // Store the instance handle
  g_hInstance = hInstance;

  return TRUE;
}

void GameStart(HWND hWindow)
{
  // Create and load the background and saucer bitmaps
  HDC hDC = GetDC(hWindow);
  g_pBackground = new Bitmap(hDC, IDB_BACKGROUND, g_hInstance);
  g_pSaucer = new Bitmap(hDC, IDB_SAUCER, g_hInstance);

  // Set the initial saucer position and speed
  g_iSaucerX = 250 - (g_pSaucer->GetWidth() / 2);
  g_iSaucerY = 200 - (g_pSaucer->GetHeight() / 2);
  g_iSpeedX = 0;
  g_iSpeedY = 0;
}

void GameEnd()
{
  // Cleanup the background and saucer bitmaps
  delete g_pBackground;
  delete g_pSaucer;

  // Cleanup the game engine
  delete g_pGame;
}

void GameActivate(HWND hWindow)
{
}

void GameDeactivate(HWND hWindow)
{
}

void GamePaint(HDC hDC)
{
  // Draw the background and saucer bitmaps
  g_pBackground->Draw(hDC, 0, 0);
  g_pSaucer->Draw(hDC, g_iSaucerX, g_iSaucerY, TRUE);
}

void GameCycle()
{
  // 更新飞碟位置
  g_iSaucerX = min(500 - g_pSaucer->GetWidth(), max(0, g_iSaucerX + g_iSpeedX));
  g_iSaucerY = min(320, max(0, g_iSaucerY + g_iSpeedY));

  // Force a repaint to redraw the saucer
  InvalidateRect(g_pGame->GetWindow(), NULL, FALSE);
}

void HandleKeys()
{
  // Change the speed of the saucer in response to arrow key presses
  if (GetAsyncKeyState(VK_LEFT) < 0)
    g_iSpeedX = max(-g_iMAXSPEED, --g_iSpeedX);
  else if (GetAsyncKeyState(VK_RIGHT) < 0)
    g_iSpeedX = min(g_iMAXSPEED, ++g_iSpeedX);
  if (GetAsyncKeyState(VK_UP) < 0)
    g_iSpeedY = max(-g_iMAXSPEED, --g_iSpeedY);
  else if (GetAsyncKeyState(VK_DOWN) < 0)
    g_iSpeedY = min(g_iMAXSPEED, ++g_iSpeedY);
}

void MouseButtonDown(int x, int y, BOOL bLeft)
{
  if (bLeft)
  {
    //鼠标左键事件
    // Set the saucer position to the mouse position
    g_iSaucerX = x - (g_pSaucer->GetWidth() / 2);
    g_iSaucerY = y - (g_pSaucer->GetHeight() / 2);
  }
  else
  {
    // Stop the saucer
    g_iSpeedX = 0;
    g_iSpeedY = 0;
  }
}

void MouseButtonUp(int x, int y, BOOL bLeft)
{
}

void MouseMove(int x, int y)
{
}

//-----------------------------------------------------------------
// UFO Resource Identifiers
// C++ Header - Resource.h
//-----------------------------------------------------------------

//-----------------------------------------------------------------
// Icons                    Range : 1000 - 1999
//-----------------------------------------------------------------
#define IDI_UFO             1000
#define IDI_UFO_SM          1001

//-----------------------------------------------------------------
// Bitmaps                  Range : 2000 - 2999
//-----------------------------------------------------------------
#define IDB_BACKGROUND      2000
#define IDB_SAUCER          2001

//-----------------------------------------------------------------
// UFO Resources
// RC Source - UFO.rc
//-----------------------------------------------------------------

//-----------------------------------------------------------------
// Include Files
//-----------------------------------------------------------------
#include "Resource.h"

//-----------------------------------------------------------------
// Icons
//-----------------------------------------------------------------
IDI_UFO            ICON         "Res//UFO.ico"
IDI_UFO_SM         ICON         "Res//UFO_sm.ico"

//-----------------------------------------------------------------
// Bitmaps
//-----------------------------------------------------------------
IDB_BACKGROUND     BITMAP       "Res//Background.bmp"
IDB_SAUCER         BITMAP       "Res//Saucer.bmp"