求助《windows程序设计》里的一个例子

问题在红色字样那里
/*------------------------------------------
   ABOUT2.C -- About Box Demo Program No. 2
               (c) Charles Petzold, 1998
  ------------------------------------------*/

#include <windows.h>
#include "resource.h"LRESULT CALLBACK WndProc      (HWND, UINT, WPARAM, LPARAM) ;
BOOL    CALLBACK AboutDlgProc (HWND, UINT, WPARAM, LPARAM) ;

int iCurrentColor  = IDC_BLACK,
    iCurrentFigure = IDC_RECT ;int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("About2") ;
     MSG          msg ;
     HWND         hwnd ;
     WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (hInstance, szAppName) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = szAppName ;
     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("This program requires Windows NT!"),
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }

     hwnd = CreateWindow (szAppName, TEXT ("About Box Demo Program"),
                          WS_OVERLAPPEDWINDOW,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;

     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;

     while (GetMessage (&msg, NULL, 0, 0))
     {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
     }
     return msg.wParam ;
}void PaintWindow (HWND hwnd, int iColor, int iFigure)
{
     static COLORREF crColor[8] = { RGB (  0,   0, 0), RGB (  0,   0, 255),
                                    RGB (  0, 255, 0), RGB (  0, 255, 255),
                                    RGB (255,   0, 0), RGB (255,   0, 255),
                                    RGB (255, 255, 0), RGB (255, 255, 255) } ;     HBRUSH          hBrush ;
     HDC             hdc ;
     RECT            rect ;

     hdc = GetDC (hwnd) ;
     GetClientRect (hwnd, &rect) ;
     hBrush = CreateSolidBrush (crColor[iColor - IDC_BLACK]) ;
     hBrush = (HBRUSH) SelectObject (hdc, hBrush) ;

     if (iFigure == IDC_RECT)
          Rectangle (hdc, rect.left, rect.top, rect.right, rect.bottom) ;
     else
          Ellipse   (hdc, rect.left, rect.top, rect.right, rect.bottom) ;

     DeleteObject (SelectObject (hdc, hBrush)) ;
     ReleaseDC (hwnd, hdc) ;
}void PaintTheBlock (HWND hCtrl, int iColor, int iFigure)
{
     InvalidateRect (hCtrl, NULL, 0) ;
     UpdateWindow (hCtrl) ;                         /*我知道这里的作用是擦去对话框上空白文本控件后再重画，可是当我把UpdateWindow (hCtrl) ;这句注释掉之后对话框上的空白文本控件就什么都显示不出来了这是为什么？下面的paintwindow仍然会执行画图操作啊但没有显示出图像。求教！*/     PaintWindow (hCtrl, iColor, iFigure);
MessageBeep(-1);
}LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     static HINSTANCE hInstance ;
     PAINTSTRUCT      ps ;

     switch (message)
     {
     case WM_CREATE:
          hInstance = ((LPCREATESTRUCT) lParam)->hInstance ;
          return 0 ;

     case WM_COMMAND:
          switch (LOWORD (wParam))
          {
          case IDM_APP_ABOUT:
               if (DialogBox (hInstance, TEXT ("AboutBox"), hwnd, AboutDlgProc))
                    InvalidateRect (hwnd, NULL, TRUE) ;
               return 0 ;
          }
          break ;

     case WM_PAINT:
          BeginPaint (hwnd, &ps) ;
          EndPaint (hwnd, &ps) ;

          PaintWindow (hwnd, iCurrentColor, iCurrentFigure) ;
          return 0 ;

     case WM_DESTROY:
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}BOOL CALLBACK AboutDlgProc (HWND hDlg, UINT message,
                            WPARAM wParam, LPARAM lParam)
{
     static HWND hCtrlBlock ;
     static int  iColor, iFigure ;

     switch (message)
     {
     case WM_INITDIALOG:
          iColor  = iCurrentColor ;
          iFigure = iCurrentFigure ;

          CheckRadioButton (hDlg, IDC_BLACK, IDC_WHITE,   iColor) ;
          CheckRadioButton (hDlg, IDC_RECT,  IDC_ELLIPSE, iFigure) ;

          hCtrlBlock = GetDlgItem (hDlg, IDC_PAINT) ;

          SetFocus (GetDlgItem (hDlg, iColor)) ;
          return FALSE ;

     case WM_COMMAND:
          switch (LOWORD (wParam))
          {
          case IDOK:
               iCurrentColor  = iColor ;
               iCurrentFigure = iFigure ;
               EndDialog (hDlg, TRUE) ;
               return TRUE ;

          case IDCANCEL:
               EndDialog (hDlg, FALSE) ;
               return TRUE ;

          case IDC_BLACK:
          case IDC_RED:
          case IDC_GREEN:
          case IDC_YELLOW:
          case IDC_BLUE:
          case IDC_MAGENTA:
          case IDC_CYAN:
          case IDC_WHITE:
               iColor = LOWORD (wParam) ;
               CheckRadioButton (hDlg, IDC_BLACK, IDC_WHITE, LOWORD (wParam)) ;
               PaintTheBlock (hCtrlBlock, iColor, iFigure) ;
               return TRUE ;

          case IDC_RECT:
          case IDC_ELLIPSE:
               iFigure = LOWORD (wParam) ;
               CheckRadioButton (hDlg, IDC_RECT, IDC_ELLIPSE, LOWORD (wParam)) ;
               PaintTheBlock (hCtrlBlock, iColor, iFigure) ;
               return TRUE ;
          }
          break ;

     case WM_PAINT:
          PaintTheBlock (hCtrlBlock, iColor, iFigure) ;
          break ;
     }
     return FALSE ;
}资源文件如下：//Microsoft Developer Studio generated resource script.
//
#include "resource.h"#define APSTUDIO_READONLY_SYMBOLS
/////////////////////////////////////////////////////////////////////////////
//
// Generated from the TEXTINCLUDE 2 resource.
//
#include "afxres.h"/////////////////////////////////////////////////////////////////////////////
#undef APSTUDIO_READONLY_SYMBOLS/////////////////////////////////////////////////////////////////////////////
// English (U.S.) resources#if !defined(AFX_RESOURCE_DLL) || defined(AFX_TARG_ENU)
#ifdef _WIN32
LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
#pragma code_page(1252)
#endif //_WIN32#ifdef APSTUDIO_INVOKED
/////////////////////////////////////////////////////////////////////////////
//
// TEXTINCLUDE
//1 TEXTINCLUDE DISCARDABLE
BEGIN
    "resource.h\0"
END2 TEXTINCLUDE DISCARDABLE
BEGIN
    "#include ""afxres.h""\r\n"
    "\0"
END3 TEXTINCLUDE DISCARDABLE
BEGIN
    "\r\n"
    "\0"
END#endif    // APSTUDIO_INVOKED
/////////////////////////////////////////////////////////////////////////////
//
// Dialog
//ABOUTBOX DIALOG DISCARDABLE  32, 32, 200, 234
STYLE DS_MODALFRAME | WS_POPUP | WS_CAPTION
FONT 8, "MS Sans Serif"
BEGIN
    ICON            "ABOUT2",IDC_STATIC,7,7,20,20
    CTEXT           "About2",IDC_STATIC,57,12,86,8
    CTEXT           "About Box Demo Program",IDC_STATIC,7,40,186,8
    LTEXT           "",IDC_PAINT,114,67,72,72
    GROUPBOX        "&Color",IDC_STATIC,7,60,84,143
    RADIOBUTTON     "&Black",IDC_BLACK,16,76,64,8,WS_GROUP | WS_TABSTOP
    RADIOBUTTON     "B&lue",IDC_BLUE,16,92,64,8
    RADIOBUTTON     "&Green",IDC_GREEN,16,108,64,8
    RADIOBUTTON     "Cya&n",IDC_CYAN,16,124,64,8
    RADIOBUTTON     "&Red",IDC_RED,16,140,64,8
    RADIOBUTTON     "&Magenta",IDC_MAGENTA,16,156,64,8
    RADIOBUTTON     "&Yellow",IDC_YELLOW,16,172,64,8
    RADIOBUTTON     "&White",IDC_WHITE,16,188,64,8
    GROUPBOX        "&Figure",IDC_STATIC,109,156,84,46,WS_GROUP
    RADIOBUTTON     "Rec&tangle",IDC_RECT,116,172,65,8,WS_GROUP | WS_TABSTOP
    RADIOBUTTON     "&Ellipse",IDC_ELLIPSE,116,188,64,8
    DEFPUSHBUTTON   "OK",IDOK,35,212,50,14,WS_GROUP
    PUSHBUTTON      "Cancel",IDCANCEL,113,212,50,14,WS_GROUP
END
/////////////////////////////////////////////////////////////////////////////
//
// Icon
//// Icon with lowest ID value placed first to ensure application icon
// remains consistent on all systems.
ABOUT2                  ICON    DISCARDABLE     "About2.ico"/////////////////////////////////////////////////////////////////////////////
//
// Menu
//ABOUT2 MENU DISCARDABLE
BEGIN
    POPUP "&Help"
    BEGIN
        MENUITEM "&About",                      IDM_APP_ABOUT
    END
END
/////////////////////////////////////////////////////////////////////////////
//
// DESIGNINFO
//#ifdef APSTUDIO_INVOKED
GUIDELINES DESIGNINFO DISCARDABLE
BEGIN
    "ABOUTBOX", DIALOG
    BEGIN
        LEFTMARGIN, 7
        RIGHTMARGIN, 193
        TOPMARGIN, 7
        BOTTOMMARGIN, 227
    END
END
#endif    // APSTUDIO_INVOKED#endif    // English (U.S.) resources
/////////////////////////////////////////////////////////////////////////////#ifndef APSTUDIO_INVOKED
/////////////////////////////////////////////////////////////////////////////
//
// Generated from the TEXTINCLUDE 3 resource.
//
/////////////////////////////////////////////////////////////////////////////
#endif    // not APSTUDIO_INVOKED

解决方案 »

免费领取超大流量手机卡，每月29元包185G流量+100分钟通话, 中国电信官方发货

体会一下最后一句话
void UpdateWindow( );ResUpdates the client area by sending aWM_PAINT message if the update region is not empty. The UpdateWindow member function sends a WM_PAINT message directly, bypassing the application queue. If the update region is empty, WM_PAINT is not sent.
我懂这个函数啊若果有无效区域的话发送wm_paint 强制马上重绘  可这和我的问题有什么关系？我的问题是为什么吧这句去掉了之后对话框上的空白文本控件就什么都显示不出来了？下面的PaintWindow (hCtrl, iColor, iFigure);仍会执行画图操作
InvalidateRect 的作用是无效窗口客户区，发送低优先级的WM_PAINT消息  UpdateWindow的作用是马上重绘同时使客户区有效。注意下面的PaintWindow 函数，函数用GetDC得到设备环境句柄，这里就是关键。GetDC和BeginPaint不同，从GetDC返回句柄之后你可以用此句柄在客户区任何地方绘图，不管是有效区还是无效区，同时GetDC不会使无效区有效化。所以你把 UpdateWindow去掉了，下面的PaintWindow仍然执行，只不过画完图之后你的子窗口控件客户区已然是无效的，这就导致系统发送一条WM_PAINT消息到子窗口的窗口过程，默认的窗口过程会用画刷填充，这里应该是和背景色相同的画刷所以什么都显示不了。
经过验证我的推断是正确的
可以在 PaintWindow  里面绘完图之后加上这句：ValidateRect(hwnd,&rect); 就可以显示了。不过因为没有擦除原有背景画椭圆的时候四个角会被之前的矩形填充。
#4楼说的很好，你试试：
void PaintTheBlock (HWND hCtrl, int iColor, int iFigure)
{
InvalidateRect (hCtrl, NULL, FALSE);//TRUE) ;
// ValidateRect (hCtrl, NULL) ;
UpdateWindow (hCtrl) ;
PaintWindow (hCtrl, iColor, iFigure) ;
}
现在PaintWindow就可以画出来了。
这个很奇妙啊，要不试试INVALIDATE改为TRUE试试？

求助 《windows程序设计》里的一个例子

解决方案 »

求助《windows程序设计》里的一个例子