问题
I'm stuck with a strange problem. I'm making a Win32 application in VC++ 2008, making a class to encapsulate most of the work for easy repetition when calling a MessageBox. The message box` is created (I think) but doesn't show up unless I press the Alt key!
What happen exactly is :
I run the program
press Enter
the main window lose focus
give beep sound when i click on the main window as if a modal MessageBox is present
either press Escape... focus is gained OR press Alt then the MessageBox appear with alt key pressed (i.e. menu will drop )!!!!!!
P.S. It was working fine but suddenly this happened. I didn't find any difference - I even made a new project!
This is supposed the Main program:
int APIENTRY _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
MSG msg;
CWnd cMainWindow(TEXT("DentoMan"), TEXT("Bejkoman")); // pass The class name and window name to the constructor
cMainWindow.CreateDef(); //Create the Window
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return (int)msg.wParam;
}
While This is the Class file
CWnd::CWnd() {
};
CWnd::CWnd(LPTSTR lpszClassName, LPTSTR lpszWindowName) {
CWnd::lpszClassName = lpszClassName;
CWnd::lpszWindowName = lpszWindowName;
};
CWnd::~CWnd() {
};
// Create the window with default parameters
HWND CWnd::CreateDef(void) {
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = StaticWndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = (HINSTANCE)GetModuleHandle(NULL);
wcex.hIcon = 0;
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 4);
wcex.lpszMenuName = 0;
wcex.lpszClassName = lpszClassName;
wcex.hIconSm = 0;
RegisterClassEx(&wcex);
g_hWnd = CreateWindowEx(0,lpszClassName, lpszWindowName, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, wcex.hInstance, this);
hInst = wcex.hInstance; //Store hInstance in the class hInst variable
if (!g_hWnd) return false;
ShowWindow(g_hWnd, SW_SHOW);
UpdateWindow(g_hWnd);
return g_hWnd;
}
LRESULT CALLBACK CWnd::StaticWndProc(HWND hWnd, UINT Message, WPARAM wParam, LPARAM lParam) {
/* The Only Message we take here so we store the 'this' pointer within the window to identify messages
comming from it by the 'this' pointer*/
if ( Message == WM_CREATE ) {
SetWindowLong( hWnd, GWL_USERDATA, (LONG)((CREATESTRUCT FAR *)lParam)->lpCreateParams);
}
/* Store the window pointer in the class pointer we just created in order to run the right public WndPRoc */
CWnd *Destination = (CWnd*)GetWindowLong( hWnd, GWL_USERDATA );
// If the hWnd has a related class, pass it through
if (Destination) {
return Destination->WndProc( hWnd, Message, wParam, lParam );
}
// No destination found, defer to system...
return DefWindowProc( hWnd, Message, wParam, lParam );
};
LRESULT CWnd::WndProc(HWND hWnd, UINT Message, WPARAM wParam, LPARAM lParam) {
// Determine message type
switch (Message) {
case WM_LBUTTONDOWN:
{
/* this is a common trick for easy dragging of the window.this message fools windows telling that the user is
actually dragging the application caption bar.*/
SendMessage(hWnd, WM_NCLBUTTONDOWN, HTCAPTION,NULL);
break;
}
/*case WM_CREATE:
break;
*/
case WM_CLOSE:
PostQuitMessage(0);
break;
case WM_DESTROY:
UnregisterClass(lpszClassName, hInst);
PostQuitMessage(0);
break;
case WM_KEYDOWN: //KeyBoard keys
// Which key was pressed?
switch (wParam) {
case VK_ESCAPE: //close through escape key
PostQuitMessage(0);
return 0;
case VK_RETURN:
MessageBox(hWnd, TEXT("DFGDGD"), TEXT("DFGDFG"), NULL);
return 0;
} // End Switch
break;
case WM_COMMAND:
/*switch(LOWORD(wParam))
{
}*/
break;
case WM_PAINT:
break;
default:
return DefWindowProc(hWnd, Message, wParam, lParam);
} // End Message Switch
return 0;
};
The Class Header:
class CWnd {
public:
CWnd();
CWnd(LPTSTR lpszClassName, LPTSTR lpszWindowName);
virtual ~CWnd();
virtual HWND CreateDef(void); // Create the window with default parameters
virtual LRESULT WndProc(HWND hWnd, UINT Message, WPARAM wParam, LPARAM lParam );
private:
static LRESULT CALLBACK StaticWndProc(HWND hWnd, UINT Message, WPARAM wParam, LPARAM lParam);
HWND g_hWnd; //Global window handle for this window
HINSTANCE hInst; //Global instance for this window
LPTSTR lpszClassName;
LPTSTR lpszWindowName;
};
P.S. I included all needed header files, everything goes fine except MessageBox
This is also a link to the code on here
回答1:
Ohhhhhhh finally i found the solution of this problem ... and for everyone to benefit the problem was in WndProc(.......) at the WM_PAINT Message i wrote some code in it and removed all the code along with BeginPaint and EndPaint functions so the program enter a freeze period once anything is being painted over it including that MessageBox but it only show when i press Alt i think coz the control is transfered to the system in that step to show the system Menu (i think)
the solution either remove the WM_PAINT message handler or add the normal BeginPaint and EndPaint functions
Thanks for everyone who passed on my question
回答2:
If anyone is still interested, this method works:
MessageBox(NULL,L"error",L"Error",MB_ICONERROR|MB_DEFAULT_DESKTOP_ONLY);
回答3:
I had a similar problem that was cause by WM_PAINT as somebody above mentioned. Solved it by adding return DefWindowProc(hWnd, Message, wParam, lParam); there.
回答4:
When you create your MessageBox you should pass WS_CHILD in CreateWindowEx.
EDIT 2:
Ok try this.
MessageBox(hWnd, TEXT("DFGDGD"), TEXT("DFGDFG"), MB_OK);
来源：https://stackoverflow.com/questions/4299915/win32-messagebox-doesnt-appear