这是WINDOWS程序设计里第6章鼠标测试里的一段代码，我想测试一下WM_SETFOCUS消息的触发条件，就在父窗口的消息处理函数里的WM_SETFOCUS后面加了几行代码，结果确在弹出一个窗口后点确定又会弹出，如此一共会弹出16个，这是什么意思啊，难道父窗口里产生了16个WM_SETFOCUS消息？或者是我对窗口的某些操作导致它又产生了WM_SETFOCUS消息？还有就是为什么子窗口创建后再点击子窗口，父窗口没有接收到WM_SETFOCUS消息?
我记得programming windows上的原话是"实际上当你在子窗口上单击的时候,情况有些复杂,这是是父窗口而不是自窗口获取焦点"难道说这句话有问题？#include <windows.h>#define DIVISIONS 5
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;LRESULT CALLBACK ChildWndProc (HWND, UINT, WPARAM, LPARAM) ;int idFocus = 0 ;TCHAR szChildClass[] = TEXT ("Checker4_Child") ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,PSTR szCmdLine, int iCmdShow){static TCHAR szAppName[] = TEXT ("Checker4") ;HWND hwnd ;MSG msg ;WNDCLASS wndclass ;wndclass.style = CS_HREDRAW | CS_VREDRAW ;wndclass.lpfnWndProc = WndProc ;wndclass.cbClsExtra = 0 ;wndclass.cbWndExtra = 0 ;wndclass.hInstance = hInstance ;wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;wndclass.lpszMenuName = NULL ;wndclass.lpszClassName = szAppName ;if (!RegisterClass (&wndclass)){MessageBox (NULL, TEXT ("Program requires Windows NT!"),szAppName, MB_ICONERROR) ;return 0 ;}wndclass.lpfnWndProc = ChildWndProc ;wndclass.cbWndExtra = sizeof (long) ;wndclass.hIcon = NULL ;wndclass.lpszClassName = szChildClass ;RegisterClass (&wndclass) ;hwnd = CreateWindow (szAppName, TEXT ("Checker4 Mouse Hit-Test Demo"),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 ;}
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam,LPARAM lParam){static HWND hwndChild[DIVISIONS][DIVISIONS] ;int cxBlock, cyBlock, x, y ;HWND hwnd1;switch (message){case WM_CREATE :for (x = 0 ; x < DIVISIONS ; x++)for (y = 0 ; y < DIVISIONS ; y++)hwndChild[x][y] = CreateWindow (szChildClass, NULL,WS_CHILDWINDOW | WS_VISIBLE,0, 0, 0, 0,hwnd, (HMENU) (y << 8 | x),HINSTANCE) GetWindowLong (hwnd, GWL_HINSTANCE),NULL) ;return 0 ;case WM_SIZE :cxBlock = LOWORD (lParam) / DIVISIONS ;cyBlock = HIWORD (lParam) / DIVISIONS ;for (x = 0 ; x < DIVISIONS ; x++)for (y = 0 ; y < DIVISIONS ; y++)MoveWindow ( hwndChild[x][y],x * cxBlock, y * cyBlock,cxBlock, cyBlock, TRUE) ;return 0 ;case WM_LBUTTONDOWN :MessageBeep (0) ;return 0 ;
// On set-focus message, set focus to child windowcase WM_SETFOCUS:hwnd1=SetFocus (GetDlgItem (hwnd, idFocus)) ;
wsprintf((LPWSTR)buffer,L"%d",hwnd1)
MessageBox(hwnd,(LPCWSTR)buffer,(LPCWSTR)"",NULL);return 0 ;
// On key-down message, possibly change the focus window
case WM_KEYDOWN:x = idFocus & 0xFF ;y = idFocus >> 8 ;
switch (wParam){case VK_UP: y-- ; break ;case VK_DOWN: y++ ; break ;case VK_LEFT: x-- ; break ;case VK_RIGHT: x++ ; break ;case VK_HOME: x = y = 0 ; break ;case VK_END: x = y = DIVISIONS - 1 ; break ;default: return 0 ;}
x = (x + DIVISIONS) % DIVISIONS ;y = (y + DIVISIONS) % DIVISIONS ;
idFocus = y << 8 | x ;
SetFocus (GetDlgItem (hwnd, idFocus)) ;return 0 ;
case WM_DESTROY :PostQuitMessage (0) ;return 0 ;}return DefWindowProc (hwnd, message, wParam, lParam) ;}
LRESULT CALLBACK ChildWndProc (HWND hwnd, UINT message,WPARAM wParam, LPARAM lParam){HDC hdc ;PAINTSTRUCT ps ;RECT rect ;switch (message){case WM_CREATE :SetWindowLong (hwnd, 0, 0) ; // on/off flagreturn 0 ;
case WM_KEYDOWN:// Send most key presses to the parent windowif (wParam != VK_RETURN && wParam != VK_SPACE){SendMessage (GetParent (hwnd), message, wParam, lParam) ;return 0 ;}// For Return and Space, fall through to toggle the squarecase WM_LBUTTONDOWN :SetWindowLong (hwnd, 0, 1 ^ GetWindowLong (hwnd, 0)) ;SetFocus (hwnd) ;InvalidateRect (hwnd, NULL, FALSE) ;return 0 ;
// For focus messages, invalidate the window for repaintcase WM_SETFOCUS:idFocus = GetWindowLong (hwnd, GWL_ID) ;
// Fall through
case WM_KILLFOCUS:InvalidateRect (hwnd, NULL, TRUE) ;return 0 ;case WM_PAINT :hdc = BeginPaint (hwnd, &ps) ;GetClientRect (hwnd, &rect) ;Rectangle (hdc, 0, 0, rect.right, rect.bottom) ;
// Draw the "x" if (GetWindowLong (hwnd, 0)){MoveToEx (hdc, 0, 0, NULL) ;LineTo (hdc, rect.right, rect.bottom) ;MoveToEx (hdc, 0, rect.bottom, NULL) ;LineTo (hdc, rect.right, 0) ;}// Draw the "focus" rectangleif (hwnd == GetFocus ()){rect.left += rect.right / 10 ;rect.right -= rect.left ;rect.top += rect.bottom / 10 ;rect.bottom -= rect.top ;
SelectObject (hdc, GetStockObject (NULL_BRUSH)) ;SelectObject (hdc, CreatePen (PS_DASH, 0, 0)) ;Rectangle (hdc, rect.left, rect.top, rect.right, rect.bottom) ;DeleteObject (SelectObject (hdc, GetStockObject (BLACK_PEN))) ;}
EndPaint (hwnd, &ps) ;return 0 ;}return DefWindowProc (hwnd, message, wParam, lParam) ;}
我记得programming windows上的原话是"实际上当你在子窗口上单击的时候,情况有些复杂,这是是父窗口而不是自窗口获取焦点"难道说这句话有问题？#include <windows.h>#define DIVISIONS 5
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;LRESULT CALLBACK ChildWndProc (HWND, UINT, WPARAM, LPARAM) ;int idFocus = 0 ;TCHAR szChildClass[] = TEXT ("Checker4_Child") ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,PSTR szCmdLine, int iCmdShow){static TCHAR szAppName[] = TEXT ("Checker4") ;HWND hwnd ;MSG msg ;WNDCLASS wndclass ;wndclass.style = CS_HREDRAW | CS_VREDRAW ;wndclass.lpfnWndProc = WndProc ;wndclass.cbClsExtra = 0 ;wndclass.cbWndExtra = 0 ;wndclass.hInstance = hInstance ;wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;wndclass.lpszMenuName = NULL ;wndclass.lpszClassName = szAppName ;if (!RegisterClass (&wndclass)){MessageBox (NULL, TEXT ("Program requires Windows NT!"),szAppName, MB_ICONERROR) ;return 0 ;}wndclass.lpfnWndProc = ChildWndProc ;wndclass.cbWndExtra = sizeof (long) ;wndclass.hIcon = NULL ;wndclass.lpszClassName = szChildClass ;RegisterClass (&wndclass) ;hwnd = CreateWindow (szAppName, TEXT ("Checker4 Mouse Hit-Test Demo"),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 ;}
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam,LPARAM lParam){static HWND hwndChild[DIVISIONS][DIVISIONS] ;int cxBlock, cyBlock, x, y ;HWND hwnd1;switch (message){case WM_CREATE :for (x = 0 ; x < DIVISIONS ; x++)for (y = 0 ; y < DIVISIONS ; y++)hwndChild[x][y] = CreateWindow (szChildClass, NULL,WS_CHILDWINDOW | WS_VISIBLE,0, 0, 0, 0,hwnd, (HMENU) (y << 8 | x),HINSTANCE) GetWindowLong (hwnd, GWL_HINSTANCE),NULL) ;return 0 ;case WM_SIZE :cxBlock = LOWORD (lParam) / DIVISIONS ;cyBlock = HIWORD (lParam) / DIVISIONS ;for (x = 0 ; x < DIVISIONS ; x++)for (y = 0 ; y < DIVISIONS ; y++)MoveWindow ( hwndChild[x][y],x * cxBlock, y * cyBlock,cxBlock, cyBlock, TRUE) ;return 0 ;case WM_LBUTTONDOWN :MessageBeep (0) ;return 0 ;
// On set-focus message, set focus to child windowcase WM_SETFOCUS:hwnd1=SetFocus (GetDlgItem (hwnd, idFocus)) ;
wsprintf((LPWSTR)buffer,L"%d",hwnd1)
MessageBox(hwnd,(LPCWSTR)buffer,(LPCWSTR)"",NULL);return 0 ;
// On key-down message, possibly change the focus window
case WM_KEYDOWN:x = idFocus & 0xFF ;y = idFocus >> 8 ;
switch (wParam){case VK_UP: y-- ; break ;case VK_DOWN: y++ ; break ;case VK_LEFT: x-- ; break ;case VK_RIGHT: x++ ; break ;case VK_HOME: x = y = 0 ; break ;case VK_END: x = y = DIVISIONS - 1 ; break ;default: return 0 ;}
x = (x + DIVISIONS) % DIVISIONS ;y = (y + DIVISIONS) % DIVISIONS ;
idFocus = y << 8 | x ;
SetFocus (GetDlgItem (hwnd, idFocus)) ;return 0 ;
case WM_DESTROY :PostQuitMessage (0) ;return 0 ;}return DefWindowProc (hwnd, message, wParam, lParam) ;}
LRESULT CALLBACK ChildWndProc (HWND hwnd, UINT message,WPARAM wParam, LPARAM lParam){HDC hdc ;PAINTSTRUCT ps ;RECT rect ;switch (message){case WM_CREATE :SetWindowLong (hwnd, 0, 0) ; // on/off flagreturn 0 ;
case WM_KEYDOWN:// Send most key presses to the parent windowif (wParam != VK_RETURN && wParam != VK_SPACE){SendMessage (GetParent (hwnd), message, wParam, lParam) ;return 0 ;}// For Return and Space, fall through to toggle the squarecase WM_LBUTTONDOWN :SetWindowLong (hwnd, 0, 1 ^ GetWindowLong (hwnd, 0)) ;SetFocus (hwnd) ;InvalidateRect (hwnd, NULL, FALSE) ;return 0 ;
// For focus messages, invalidate the window for repaintcase WM_SETFOCUS:idFocus = GetWindowLong (hwnd, GWL_ID) ;
// Fall through
case WM_KILLFOCUS:InvalidateRect (hwnd, NULL, TRUE) ;return 0 ;case WM_PAINT :hdc = BeginPaint (hwnd, &ps) ;GetClientRect (hwnd, &rect) ;Rectangle (hdc, 0, 0, rect.right, rect.bottom) ;
// Draw the "x" if (GetWindowLong (hwnd, 0)){MoveToEx (hdc, 0, 0, NULL) ;LineTo (hdc, rect.right, rect.bottom) ;MoveToEx (hdc, 0, rect.bottom, NULL) ;LineTo (hdc, rect.right, 0) ;}// Draw the "focus" rectangleif (hwnd == GetFocus ()){rect.left += rect.right / 10 ;rect.right -= rect.left ;rect.top += rect.bottom / 10 ;rect.bottom -= rect.top ;
SelectObject (hdc, GetStockObject (NULL_BRUSH)) ;SelectObject (hdc, CreatePen (PS_DASH, 0, 0)) ;Rectangle (hdc, rect.left, rect.top, rect.right, rect.bottom) ;DeleteObject (SelectObject (hdc, GetStockObject (BLACK_PEN))) ;}
EndPaint (hwnd, &ps) ;return 0 ;}return DefWindowProc (hwnd, message, wParam, lParam) ;}
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同意 我刚想这么说呢。
上面的代码（当然你的buffer要增加定义）我运行后，出现了12次信息框后就不再出了。但是如果把MessageBox()的第一个参数改为NULL就是死循环，看来这个MessageBox()作为一个子窗口运行时还真有点奇怪呢。后来我定义了一个全局变量int n;，然后将MessageBox处改为
n++;
sprintf(buffer, "%d:%d", hwnd, n);
SetWindowText(hwnd, buffer);
结果窗口标题就如期显示了自己的句柄和一个1，一切正常。
至此，为何MessageBox()的第一个参数使用主窗口句柄后没有成为死循环，也就是弹出一定量的信息框后为何就中再触发WM_SETFOCUS，没搞清楚。而且我这里在这个时间窗口标题都消失了。如果切换至其它程序再切回该程序，则WM_SETFOCUS又重新恢复到以前的情况。最后，看来这个奇怪的现象是MessageBox这个函数造成的，原来如何我不知，看有哪个喜欢刨根问底的人来解开这个疑问吧。
MessageBox 不是什么地方都能用的。比如这个问题中，楼主就不该用 MessageBox 函数输出数据；可以改用其它方式，如：写文件、输出调试信息等。===========================================================不过，换句话说，能通过这个问题了解WINDOWS的底层处理机制也不错。不过，这个问题我没研究过。