C / C++ / MFC

22-Aug-05 12:03

BOOL CMyApp::InitInstance()
{
m_pMainWnd = new CMyFrameWnd;
m_pMainWnd->ShowWindow(m_nCmdShow);
m_pMainWnd->UpdateWindow();

return TRUE;
}

I change it to the next code block,but I got some error

BOOL CMyApp::InitInstance()
{
m_pMainWnd = new CMyFrameWnd;
::ShowWindow(hWnd,m_nCmdShow);
::UpdateWindow(hWnd);

return TRUE;
}

Is there any WIN32API can change "m_pMainWnd" to "hWnd"??

shanzy1980

Christian Graus22-Aug-05 12:40

22-Aug-05 12:40

It has a m_hWnd property, from memory. MFC is a wrapper for Win32, so it's all in there.

Christian Graus - Microsoft MVP - C++

shanzy22-Aug-05 12:50

22-Aug-05 12:50

Thank you!

But when I code like this:

::ShowWindow(m_hWnd,SW_SHOWNORMAL);

I got a error: error: identifier "m_hWnd" is undefined

I want to know which WIN32API can change a handle to a pointer to Class??

shanzy1980

Christian Graus22-Aug-05 13:03

22-Aug-05 13:03

I meant m_pMainWnd->m_hWnd, and I said I *think*, I expected you'd use intellisense to work out how close I was.

shanzy1980 wrote:
::ShowWindow(m_hWnd,SW_SHOWNORMAL);

Ah.... If you call ShowWindow without the ::, I think there's a method on the class. Or you can do this:

::ShowWindow(*this, SW_SHOWNORMAL);

because when you deference the point, there's an operator HWND.

shanzy1980 wrote:
I want to know which WIN32API can change a handle to a pointer to Class??

None, that can't work. Win32 came first, so the framework knows about Win32, Win32 does not know about MFC. Win32 is for use in C as well, so it cannot support classes at all.

Christian Graus - Microsoft MVP - C++

shanzy22-Aug-05 14:01

22-Aug-05 14:01

I'm a beginer,and now I read the book《Programming Windows with MF,second Edition》,this is the source code:

//myfirst.h

class CMyApp:public CWinApp
{
public:
virtual BOOL InitInstance();
};

class CMyFrameWnd:public CFrameWnd
{
public:
CMyFrameWnd();
protected:
afx_msg void OnPaint();
DECLARE_MESSAGE_MAP()
};

////////////////////////////////////////////////

#include <afxwin.h>
#include "myfirst.h"

CMyApp theApp;

BOOL CMyApp::InitInstance()
{
m_pMainWnd = new CMyFrameWnd;
::ShowWindow(*this,SW_SHOWNORMAL);
::UpdateWindow(*this);

return TRUE;
}

BEGIN_MESSAGE_MAP(CMyFrameWnd, CFrameWnd)
ON_WM_PAINT()
END_MESSAGE_MAP()

CMyFrameWnd::CMyFrameWnd()
{
Create(NULL, _T("myfirstMFC"));
}

void CMyFrameWnd::OnPaint()
{

CPaintDC mydc(this);

CRect rect;

GetClientRect(&rect);

mydc.DrawText(_T("MFC"),-1,&rect,DT_SINGLELINE|DT_CENTER|DT_VCENTER);
}

It also don't work, If you can explain with circumstances why it doesn't work

Thanks!

shanzy

Christian Graus22-Aug-05 14:03

22-Aug-05 14:03

Well, what do you mean when you say it doesn't work ? Does it have errors ? Does it not do what you're expecting ? I'll try to recreate this project locally and see what I can find, but any info you can give on the difference between what you're seeing and what you're expecting would help me to help you.

Christian Graus - Microsoft MVP - C++

shanzy22-Aug-05 14:08

22-Aug-05 14:08

I got a LINK error:

catastrophic error: #error directive: Please use the /MD switch for _AFXDLL builds
#error Please use the /MD switch for _AFXDLL builds

Christian Graus22-Aug-05 14:10

22-Aug-05 14:10

You're using VC6 Smile | :)

( I worked that out by looking at the code, not the error ). VC6 is kind of crap, but it's OK for learning. When you get to understand C++, you'll want to upgrade.

I'd say this means you have your app running at the same time as the compiler is trying to write to it, that's all. If it's not visibly running, hit CTRL-SHIFT-ESC for the task manager, look through the processes and kill it there.

Christian Graus - Microsoft MVP - C++

shanzy22-Aug-05 14:26

22-Aug-05 14:26

OK,I know it,Thank you very much!!

Jose Lamas Rios22-Aug-05 17:25

Jose Lamas Rios

22-Aug-05 17:25

shanzy1980 wrote:
I change it to the next code block,but I got some error

Why do you want to change it? MFC's CWnd (and derived classes) are wrappers around window handles (those hWnd you see here and there). I can understand that if you obtained an hWnd somehow (e.g.: creating a window yourself using one of the API functions) you may not want to create an MFC CWnd class to wrap it, but if you already have one of the CWnd objects, why would you want to use the API directly instead of using the corresponding class methods?

Anyway... In your code:

BOOL CMyApp::InitInstance()
{
   m_pMainWnd = new CMyFrameWnd;
   ::ShowWindow(hWnd,m_nCmdShow); 
   ::UpdateWindow(hWnd);
 
return TRUE;
}

After m_pMainWnd = new CMyFrameWnd, m_pMainWnd points to a CMyFrameWnd object, but the window won't be still created (unless you added some code to the class constructor to do it).

In ::ShowWindow(hWnd,m_nCmdShow); and the next line, hWnd is undefined.

The translation from CWnd methods to API calls should be like this:

BOOL CMyApp::InitInstance()
{
   m_pMainWnd = new CMyFrameWnd;
   ::ShowWindow(m_pMainWnd->m_hWnd, m_nCmdShow); 
   ::UpdateWindow(m_pMainWnd->m_hWnd);
 
return TRUE;

Hope that helps,

--
jlr
http://jlamas.blogspot.com/[^]

ThatsAlok22-Aug-05 20:13

ThatsAlok

22-Aug-05 20:13

shanzy1980 wrote:

m_pMainWnd = new CMyFrameWnd; ::ShowWindow(hWnd,m_nCmdShow); ::UpdateWindow(hWnd);

In continuation With jose!, here is one more method to achieve same as Mr. Jose stated in his last post!:-

m_pMainWnd = new CMyFrameWnd;
::ShowWindow(m_pMainWnd-><code>GetSafeHwnd()</code>,m_nCmdShow);
::UpdateWindow(m_pMainWnd-><code>GetSafeHwnd()</code>);

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

shanzy22-Aug-05 21:49

22-Aug-05 21:49

wonderful && excellent! I catch it! Thank you very much!

And Thank you : Christian Graus,Jose Lamas Rios ,ThatsAlok

shanzy

WMI

YusufK22-Aug-05 10:52

YusufK

22-Aug-05 10:52

Hi,

Using Win32_classes I have wrote a code. I have some help from msdn. I am retrieving sound card's info, up to now everything is ok. But also I need to compare "vtProp.bstrVal" with a string like "char c[30]". I think , I should convert this "vtProp.bstrVal" to a string or convert string "vtProp.bstrVal" like variable. Do you have any suggestions?

Thanx...

while (pEnumerator)
{
HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1,
&pclsObj, &uReturn);

if(0 == uReturn)
{
break;
}

VARIANT vtProp;
VariantInit(&vtProp);
c=&(vtProp.bstrVal);
// Get the value of the Name property
hr = pclsObj->Get(L"ProductName", 0, &vtProp, 0, 0);
std::wcout <

Christian Graus22-Aug-05 12:02

22-Aug-05 12:02

comutils.h contains a string class called _bstr_t. This class will take a bstr and return a char *. So

_bstr_t bt (myChar*);

Now you can cast bt to a char *.

Christian Graus - Microsoft MVP - C++

YusufK23-Aug-05 7:59

YusufK

23-Aug-05 7:59

Thank you,

But my compiler have not found comutils.h . I am using Visual Studio 6.0, should I install any extension pack?

Christian Graus23-Aug-05 13:27

23-Aug-05 13:27

I think it's comutil without the s. You should google _bstr_t for full info on it. You may need a platform SDK.

Christian Graus - Microsoft MVP - C++

MailtoGops23-Aug-05 0:14

MailtoGops

23-Aug-05 0:14

Hi,

COM implements two bytes per character method. You have to convert vtProp.bstrVal to a ANSI string.

For that you can use wcstombs() function.

Then you can do the comparision with the ANSI string that you have converted and the actual char[30] string you have.

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Vision without action is merely day dreaming,
But vision with action can change the world "

- Words from Nelson Mandela

Thanks & Regards,

Gopalakrishnan