| Back to Questions Page |
| |
| Question |
Hi All,
I have created one MFC Dialog Based application.now if i am
running the application its working fine,instead of closing
he application i minimized the application,if i run the
application again,i am getting the Dialog.
I want to prevent the calling of application multiple times.
please give me the code and let me know in which method i
need to make changes.
Praveer |
Rank |
Answer Posted By |
|
Question Submitted By :: Praveer |
| This Interview Question Asked @ HP |
|
I also faced this Question!! |
© ALL Interview .com |
| Answer | if(NULL != ::CreateMutex(NULL, TRUE,
_T("CSingleInstanceApp")))
{
long dwError = ::GetLastError();
if(dwError == ERROR_ALREADY_EXISTS)
EndDialog(IDOK);
}
Paste the above code snippet inside the "InitInstance"
function.  |
| Rajaram B |
| |
| |
| Answer | Hi,
i wrote the code as you told still its not
working,here is my code,please have a look
/////////////////////////////////////////////////////////////
BOOL CDlgApp::InitInstance()
{
AfxEnableControlContainer();
// Standard initialization
// If you are not using these features and wish to reduce
the size
// of your final executable, you should remove from the
following
// the specific initialization routines you do not need.
#ifdef _AFXDLL
Enable3dControls(); // Call this when using MFC in a
shared DLL
#else
Enable3dControlsStatic(); // Call this when linking to MFC
statically
#endif
if(NULL != ::CreateMutex(NULL, TRUE,_T("CSingleInstanceApp")))
{
long dwError = ::GetLastError();
if(dwError == ERROR_ALREADY_EXISTS)
EndDialog(NULL,IDOK);
}
CDlgDlg dlg;
m_pMainWnd = &dlg;
int nResponse = dlg.DoModal();
if (nResponse == IDOK)
{
// TODO: Place code here to handle when the dialog is
// dismissed with OK
}
else if (nResponse == IDCANCEL)
{
// TODO: Place code here to handle when the dialog is
// dismissed with Cancel
}
// Since the dialog has been closed, return FALSE so that
we exit the
// application, rather than start the application's
message pump.
return FALSE;
}
////////////////////////////////  |
| Praveer |
| |
| |
| Question |
What is CALLBACK? How it work?
what is the advantage of CALLBACK,
please explain with an example
|
Rank |
Answer Posted By |
|
Question Submitted By :: Praveer |
|
I also faced this Question!! |
© ALL Interview .com |
| Answer | • callback function is a function that is called
through a function pointer.
• pass the pointer (address) of a function as an
argument to another, when that pointer is used to call the
function it points to it is said that a call back is made.
// 2.1 define a function pointer and initialize to NULL
int (*pt2Function)(float, char, char) =
NULL; // C
int (TMyClass::*pt2Member)(float, char, char) =
NULL; // C++
int (TMyClass::*pt2ConstMember)(float, char, char) const =
NULL; // C++
• A callback function is a function that is passed
to another function (in the form of a pointer to the
callback function) so that the second function can
call it. This is simply of way of making the second
function more flexible without the second function needing
to know a lot of stuff
Uses:
• A callback can be used for notifications
• callback functions can be used for updates, sort of
like hooking into another function. For example, consider a
function that downloads files using http. Your application
may want to display progress to the user. You could pass a
callback function (display progress) into the download
function so that it calls your display function everytime
it reads from the socket. At least that is my
understanding...  |
| Zero Zero.... |
| |
| |
|
|
| |
| Question |
what are the advantages of VC++ design environment |
Rank |
Answer Posted By |
|
Question Submitted By :: Jyothi N Swamy |
|
I also faced this Question!! |
© ALL Interview .com |
| Answer | By design environment if you mean by the IDE that MS
provides then answer is quite simple. Visual Studio is one
of the most sophisticated, powerful yet simple to use IDE
for Windows programming.
Vikas
http://www.cppquestions.com/  |
| V |
| |
| |
| Question |
How WM_PAINT message gets called in MFC,please explain it .
a)Who calls the WM_PAINT message?
b)When it gets called?
c)how it comes to message queue?
Please Explain it |
Rank |
Answer Posted By |
|
Question Submitted By :: Praveer |
|
I also faced this Question!! |
© ALL Interview .com |
| Answer | a)The framework calls this member function
b)This function get called, when Windows or an application
makes a request to repaint a portion of an application's
window.
c)  |
| Sai |
| |
| |
| Answer | WM_Paint Message will be invoked by the system and not by
any application.
This message is sent when updatewindow or RedrawWindow
Function is called.
Dispactch Message Function dispatches the message , it gets
the message from the GetMessage() or PeekMessage()
Functions.  |
| Vijay |
| |
| |
| Question |
1)why we cant create more than one instance of the class
Derived from CWinApp
|
Rank |
Answer Posted By |
|
Question Submitted By :: Praveer |
|
I also faced this Question!! |
© ALL Interview .com |
| Answer | You theApp object is replace with new name;
Eg
CdlgtestApp theApp;
CdlgtestApp theApp3; // now this is your applcation obj
CdlgtestApp theApp3;
CdlgtestApp theApp; // No effect  |
| Narayan |
| |
| |
| Question |
I have to DLL one is COM dll and another is normal DLL.
How I can identify which dll is normal DLL and which DLL is
from COM DLL.
please give me some clear picture on these
|
Rank |
Answer Posted By |
|
Question Submitted By :: Mohammed Shafi |
|
I also faced this Question!! |
© ALL Interview .com |
| Answer | make command on both dll
regsvr("noramal dll") it will show message of some entry
point error
regsvr("comdll") it will register succesfully to window  |
| Chetan |
| |
| |
| Question |
Differ GetMessage, PostMessage & PeakMessage? |
Rank |
Answer Posted By |
|
Question Submitted By :: Td |
| This Interview Question Asked @ Symphony |
|
I also faced this Question!! |
© ALL Interview .com |
| Answer | PostMessage is used in Threading usually. to post a message
to Messaging Queue.
Get message is a blocking call it waits for the message
untill it recieve the message it was requiring
Peak message doesnt wait for the message particually it is
looking it just look if the particular message is not in the
queue it returns.  |
| Rao Naeem |
| |
| |
|
| |
|
Back to Questions Page |