VC++游戏编程基础子弹贴图问题！

Question

我没有搞清楚子弹是如何循环贴图的？
首先来看看子弹结构体及消息处理函数产生子弹的部分:

      struct BULLET//定义子弹结构体
       {
              int x,y;
                bool exist;
       };

      case WM_LBUTTONDOWN:          
               for(i=0;i<30;i++)
             {
                    if(!b[i].exist)
                 {
                         b[i].x = nowX;     
                         b[i].y = nowY + 30; 
                         b[i].exist = true;
                         bcount++;          
                         break;
                  }
           }

分析：b[30]为子弹结构体数组单击鼠标左键，此时产生了第一颗子弹b[0],然后问题是break退出循环，那么i只能等于零，那这个循环有什么意义？然后退出for循环这时候回到贴图函数中，看看这一颗子弹是如何循环贴图的。

SelectObject(bufdc,bullet);
    if(bcount!=0)
        for(i=0;i<30;i++)

            if(b[i].exist)
            {

                BitBlt(mdc,b[i].x,b[i].y,10,10,bufdc,0,10,SRCAND);
                BitBlt(mdc,b[i].x,b[i].y,10,10,bufdc,0,0,SRCPAINT);

                b[i].x -= 10;
                if(b[i].x < 0)
                {
                    bcount--;
                    b[i].exist = false;
                }
            }

分析：由于产生了一颗子弹，bcount=1,执行for循环；i=0的时候，对子弹进行贴图，在mdc上贴完之后，子弹坐标要向左递减10个单位(这个时候我认为只是改变了坐标，要改变子弹位置要根据这个坐标再一次贴图)，然后继续循环，问题就在这里，此时i=1,我觉得b[1]和b[0]压根就没有任何关系，这个循环应该是对b[0]进行循环贴图直到它消失。

请各位高手指教！！！！！

游戏的源码如下：

#include "stdafx.h"
#include <stdio.h>


struct BULLET//定义子弹结构体
{
    int x,y;
    bool exist;
};


HINSTANCE hInst;
HBITMAP bg,ship,bullet;
HDC     hdc,mdc,bufdc;
HWND    hWnd;
DWORD   tPre,tNow;
int     x,y,nowX,nowY;//光标坐标,飞机贴图坐标
int     w=0,bcount;//w为滚动背景所要裁剪的宽度；记录飞机现有的子弹数目
BULLET  b[30];//存储飞机发出的子弹

ATOM                MyRegisterClass(HINSTANCE hInstance);
BOOL                InitInstance(HINSTANCE, int);
LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
void                MyPaint(HDC hdc);


int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
    MSG msg;

    MyRegisterClass(hInstance);


    if (!InitInstance (hInstance, nCmdShow)) 
    {
        return FALSE;
    }


    while( msg.message!=WM_QUIT )
    {
        if( PeekMessage( &msg, NULL, 0,0 ,PM_REMOVE) )
        {
            TranslateMessage( &msg );
            DispatchMessage( &msg );
        }
        else
        {
            tNow = GetTickCount();
            if(tNow-tPre >= 40)
                MyPaint(hdc);
        }
    }

    return msg.wParam;
}


ATOM MyRegisterClass(HINSTANCE hInstance)
{
    WNDCLASSEX wcex;

    wcex.cbSize = sizeof(WNDCLASSEX); 
    wcex.style          = CS_HREDRAW | CS_VREDRAW | CS_DBLCLKS;
    wcex.lpfnWndProc    = (WNDPROC)WndProc;
    wcex.cbClsExtra     = 0;
    wcex.cbWndExtra     = 0;
    wcex.hInstance      = hInstance;
    wcex.hIcon          = NULL;
    wcex.hCursor        = NULL;
    wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
    wcex.lpszMenuName   = NULL;
    wcex.lpszClassName  = "canvas";
    wcex.hIconSm        = NULL;

    return RegisterClassEx(&wcex);
}


BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
    HBITMAP bmp;
    POINT pt,lt,rb;
    RECT rect;

    hInst = hInstance;

    hWnd = CreateWindow("canvas", "酶瓜跌怠" , WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);

    if (!hWnd)
    {
        return FALSE;
    }

    MoveWindow(hWnd,10,10,640,480,true);
    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

    hdc = GetDC(hWnd);
    mdc = CreateCompatibleDC(hdc);
    bufdc = CreateCompatibleDC(hdc);

    bmp = CreateCompatibleBitmap(hdc,640,480);
    SelectObject(mdc,bmp);

    bg = (HBITMAP)LoadImage(NULL,"bg.bmp",IMAGE_BITMAP,648,480,LR_LOADFROMFILE);
    ship = (HBITMAP)LoadImage(NULL,"ship.bmp",IMAGE_BITMAP,100,148,LR_LOADFROMFILE);
    bullet = (HBITMAP)LoadImage(NULL,"bullet.bmp",IMAGE_BITMAP,10,20,LR_LOADFROMFILE);

    x = 300;              
    y = 300;
    nowX = 300;
    nowY = 300;

    ////设定鼠标光标位置
    pt.x = 300;
    pt.y = 300;
    ClientToScreen(hWnd,&pt);//把窗口坐标转化为屏幕坐标，因为SetCursorPos只认屏幕坐标
    SetCursorPos(pt.x,pt.y);

    ShowCursor(false);      //隐藏鼠标光标

    //限制鼠标光标移动区域
    GetClientRect(hWnd,&rect);//获取客户区窗口的大小
    lt.x = rect.left;
    lt.y = rect.top;
    rb.x = rect.right;
    rb.y = rect.bottom;
    ClientToScreen(hWnd,&lt);
    ClientToScreen(hWnd,&rb);
    rect.left = lt.x;
    rect.top = lt.y;
    rect.right = rb.x;
    rect.bottom = rb.y;
    ClipCursor(&rect);//限制鼠标在矩形区域内

    MyPaint(hdc);

    return TRUE;
}


void MyPaint(HDC hdc)
{
    char str[20] = "";
    int i;


    SelectObject(bufdc,bg);
    BitBlt(mdc,0,0,w,480,bufdc,640-w,0,SRCCOPY);
    BitBlt(mdc,w,0,640-w,480,bufdc,0,0,SRCCOPY);

    //飞机贴图缓慢向鼠标移动
    if(nowX < x)
    {
        nowX += 10;
        if(nowX > x)
            nowX = x;
    }
    else
    {
        nowX -=10;
        if(nowX < x)
            nowX = x;
    }

    if(nowY < y)
    {
        nowY += 10;
        if(nowY > y)
            nowY = y;
    }
    else
    {
        nowY -= 10;
        if(nowY < y)
            nowY = y;
    }


    SelectObject(bufdc,ship);
    BitBlt(mdc,nowX,nowY,100,74,bufdc,0,74,SRCAND);
    BitBlt(mdc,nowX,nowY,100,74,bufdc,0,0,SRCPAINT);

    SelectObject(bufdc,bullet);
    if(bcount!=0)
        for(i=0;i<30;i++)

            if(b[i].exist)
            {

                BitBlt(mdc,b[i].x,b[i].y,10,10,bufdc,0,10,SRCAND);
                BitBlt(mdc,b[i].x,b[i].y,10,10,bufdc,0,0,SRCPAINT);

                b[i].x -= 10;
                if(b[i].x < 0)
                {
                    bcount--;
                    b[i].exist = false;
                }
            }



    sprintf(str,"X畒夹%d    ",x);
    TextOut(mdc,0,0,str,strlen(str));
    sprintf(str,"Y畒夹%d    ",y);
    TextOut(mdc,0,20,str,strlen(str));

    BitBlt(hdc,0,0,640,480,mdc,0,0,SRCCOPY);

    tPre = GetTickCount();

    w += 10;
    if(w==640)
        w = 0;
}


LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    int i;

    switch (message)
    {
        case WM_KEYDOWN:                
            if(wParam==VK_ESCAPE)       //只要按下一次鼠标左键，都会从(nowX,nowY+30)出现一颗子弹
                PostQuitMessage(0);
            break;

        case WM_LBUTTONDOWN:            
            for(i=0;i<30;i++)
            {
                if(!b[i].exist)
                {
                    b[i].x = nowX;      
                    b[i].y = nowY + 30; 
                    b[i].exist = true;
                    bcount++;           
                    break;
                }
            }


        case WM_MOUSEMOVE:
            x = LOWORD(lParam);         
            if(x > 530)
                x = 530;
            else if(x < 0)
                x = 0;

            y = HIWORD(lParam);     
            if(y > 380)
                y = 380;
            else if(y < 0)
                y = 0;

            break;
        case WM_DESTROY:                
            ClipCursor(NULL);           

            DeleteDC(mdc);
            DeleteDC(bufdc);
            DeleteObject(bg);
            DeleteObject(bullet);
            DeleteObject(ship);
            ReleaseDC(hWnd,hdc);

            PostQuitMessage(0);
            break;
        default:                    
            return DefWindowProc(hWnd, message, wParam, lParam);
   }
   return 0;
}

Answer 1

你的break位置放错了