mfc, GetDlgItem Problem

microsoft.public.vc.mfc - Microsoft Visual C


mfc >> GetDlgItem Problem

by Scott McPhillips [MVP] » Tue, 21 Mar 2006 21:45:48 GMT

PeterOut wrote:
> I am using MSVC++ on Windows ME and have the following event handler
> for when I click on an item in a list box on a dialog box I have built.
>
> void CStereoControlPtsDlg::OnSelchangeInputImages()
> {
> CWnd *cwListBox=GetDlgItem(IDC_INPUT_IMAGES);
>
> *lpNumberOfDocumentsSelected = (long)cwListBox->SendMessage((UINT)
> LB_GETSELITEMS,
> (WPARAM)(lpNumberOfDocumentsSelected), (LPARAM) (lpSelectedIndices));
>
> }
>
> IDC_INPUT_IMAGES is the ID for the list box.
>
> For some reason I get funny values for cwListBox. That is
> cwListBox=0x00bc3ed0
> cwListBox->m_hWnd=0x00000e6c
>
> When I call cwListBox->SendMessage, the program crashes at the
> following point.
> _AFXWIN_INLINE LRESULT CWnd::SendMessage(UINT message, WPARAM wParam,
> LPARAM lParam)
> { ASSERT(::IsWindow(m_hWnd)); return ::SendMessage(m_hWnd, message,
> wParam, lParam); }
> and returns the message.


It looks like you are passing a pointer in WPARAM. A count is expected.

Your code is a mess and the error was caused by failing to use basic MFC
technique. The entire thing should look like this:

int n = m_ListBox.GetSelItems(count, lpSelectedIndices);

Since this requires no casts the compiler would have detected your error.

--
Scott McPhillips [VC++ MVP]


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mfc >> GetDlgItem Problem

by PeterOut » Wed, 22 Mar 2006 10:10:26 GMT





You are absolutely correct. That was the problem. Thanks very much.



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Similar Threads

1. GetDlgItem Problem

2. Problem when removing GetDlgItem 

Hello, all.

I've been handed an old code base, written using VC++ 1.52C and MFC.

I'm trying to clean it up and one of the things I'm trying to do is to get
rid of GetDlgItem as Joseph Newcomer advises.

Today I ran into a problem.

I added controls for two listboxes c_BaselineLB and c_TargetLB.

I replaced all the listbox pointers uses in the code and got
the following error only when I tried to use AddString() or
SetItemData() with the controls.  All other uses of the controls are
fine.

error C2662: 'SetItemData' : cannot convert 'this' pointer from 'const class
::CListBox __far *' to 'class ::CListBox __far *const '

To work around this I had to do something like the following:

((CListBox*)(&c_TargetLB))->SetItemData((c_TargetLB.GetCount() - 1), acqID);

rather than simply c_TargetLB.SetItemData((c_TargetLB.GetCount() - 1),
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which generates the error.

What am I missing here?

Thanks for any light you can shed upon this,

3. GetDlgItem() returns NULL

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CWnd* pStaticControl = GetDlgItem(IDC_SOMESTATICCONTROL);

so I switched it to

CWnd* pStaticControl =
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after that it worked fine so I decided to switch it back to the original
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Have mercy on me I'm a newbie with C++

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5. avoiding use of UpdateData() and GetdlgItem() with radiobuttons ???

6. GetDlgItem for CComboBox in Rebar? 

A combo box works better if it is not in a dialog.  You can set it up like
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Combo box is defined in the .h as:

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 if (!m_wndReBar.Create(this) ||
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RBBS_NOGRIPPER|RBBS_FIXEDBMP | RBBS_BREAK))
 {
  TRACE0("Failed to create rebar\n");
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Then you can access it with:

 m_wndAddressCombo.GetWindowText(strData);

The rebar will also resize the combo box to fit the size of the window which
is nice.

HTH,

Tom

"Michael B. Allen" < XXXX@XXXXX.COM > wrote in message
news:066001c37e22$83aa74c0$ XXXX@XXXXX.COM ...
> I want to get the text of the combo box in a toolbar. If I
> do the following:
>
>   CComboBox *combo = (CComboBox *)GetDlgItem(IDC_TARGET);
>   CString target;
>   combo->GetWindowText(target);
>
> it asserts here:
>
>   void CWnd::GetWindowText(CString& rString) const
>   {
>     ASSERT(::IsWindow(m_hWnd));  <-- error
>
> The combo box was created using the resource editor. I
> just created a dialog, dragged a combo box into it, and
> gave it an ID of IDC_TARGET.
>
> So how do I do this?
>
> Thanks,
> Mike

7. Cache hWnd from ::GetDlgItem

8. GetDlgItem and CStatic derived control 

Hello,

I have a CDialog with some custom CStatic controls inside (CStatic with
SetTextColor,SetBkColor, ..) and I would like to do something like this

GetDlgItem( IDC_LABEL1 )->SetFont("Arial", 20, FW_BOLD);
GetDlgItem( IDC_LABEL1 )->SetWindowText( m_csLabel1 );

but it cannot work since GetDlgItem returns a pointer to a CWnd.
So I tried :


CxStatic* pStatic;
pStatic = (CxStatic*)GetDlgItem( IDC_LABEL1 );
pStatic->SetFont("Arial", 20, FW_BOLD);
pStatic->SetWindowText( m_csLabel1 );


But I get a Unhandled exception 0xxxxxxx : Access violation reading 
location 0xcdcdcdcd.

And finally if I do :

CxStatic* pStatic;
pStatic = (CxStatic*)GetDlgItem( IDC_LABEL1 );
pStatic->SetFont("Arial", 20, FW_BOLD);
m_staLabel1.SetWindowText( m_csLabel1 ); //  with m_staLabel1 a control 
variable associated to IDC_LABEL1 it works fine.

Any idea ?