required/desired and explained in other posts -- and below. . .
I am working on an application for a stroke patient (my mother). I am
learning C++ and VS and MFC -- I've been a 'C' since the dino days.
So I created a button click / bitmap inverting class. -- there is a 7th
buttons. But the logic will be the same for each page -- takes two
the buttons action. The default icon will show -- when the first
click is made this icon is inverted.
"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
See below...
On Tue, 7 Apr 2009 07:48:46 -0500, "Kevin Waite"
<kevin001.waite@gmail.com> wrote:
Thank you. I think I almost understand. Rough being a newbie :)
As used -- GetSafeHwnd(); results in Unhandled exception at 0x5c5278dc
(mfc90ud.dll) in tst04.exe:
for:
gMBs.CtlBtn.m_Btn->SetBitmap( gMBs.CtlBtn.m_Btmp );
****
Does the g-name suggest it is a global variable? If so, you must STOP
what you are doing
and rethink the entire problem. A global variable would NEVER be
appropriate here, EVER!
****
gMBs.CtlBtn.m_Btn is set from:
reinterpret_cast<CButton *>(GetDlgItem(DlgH,gMBs.CtlBtn.Btn_ID));
****
Read the part of GetDlgItem where it says:
"The returned pointer may be temporary and should not be stored for later
use"
In this case, it *is* temporary, and the storage is "garbage collected"
each time you
return to your message pump. The "g" prefix suggests this is global, so
it would be
inappropriate to use a global variable, and erroneous to store a
GetDlgItem pointer in it.
The result, by the way, is an access fault.
****
within the mpc.cpp attached.
Clearly -- I am missing some large overall consideration rule or
construct.
****
(a) Don't call GetDlgItem except in extremely rare and exotic
circumstances, of which you
have not shown an example (in fact, you have shown the opposite: you are
misusing
GetDlgItem)
(b) Don't store the pointer from GetDlgItem
(c) Don't try to manipulate any control of your dialog from any class
except the dialog
class
****
I am working on an application for a stroke patient (my mother). I am
learning C++ and VS and MFC -- I've been a 'C' since the dino days.
This app defines 6 (six) jumbo size touch buttons (for now mouse click
buttons), these jumbo buttons will have a graphic bitmap (this is working)
\via this test code:
BOOL C_tst_04_Dlg::OnInitDialog()
{ . . .
static CBitmap m_bitmap;
****
It is truly had to see a line so completely erroneous in a program.
(a) NEVER, EVER declare a non-const variable as 'static' in a function
(b) It makes no sense to declare a local variable as static in a function
that is called
once
(c) m_ means "I am a member of the class" which it clearly is not!
****
CButton *m_Btn_1;
****
NO!
(a) You don't need this variable
(b) the name sucks
(c) It starts with "m_" meaning "I am a member of the class" which it
clearly is not
****
m_Btn_1 = reinterpret_cast<CButton *>(GetDlgItem(IDC_BUTTON1));
****
NO!
(a) You are using GetDlgItem
(b) You did not change the name from IDC_BUTTON1 to something sensible
****
m_bitmap.LoadBitmap(IDB_BITMAP_Btn_1);
m_Btn_1->SetBitmap(m_bitmap);
****
Write
HBITMAP bmp = (HBITMAP)::LoadImage(AfxGetInstanceHandle(),
MAKEINTRESOURCE(IDB_BITMAP_Btn_1),
IMAGE_BITMAP,
0,0,
LR_LOADMAP3DCOLORS | LR_SHARED);
ButtonWithAUsefulName.SetBitmap(bmp);
LoadBitmap has many problems, not the least of which is that it cannot
handle
high-color-depth bitmaps and it cannot change the background color to
match the user's
current theme.
****
. . . }
Because of false/error hits/taps the design is to require two discrete
taps
with the
first tape inverting the bitmap on the button -- so it becomes tagged --
the
patient gets visual feedback of what they are trying to do.
So I created a button click / bitmap inverting class. -- there is a 7th
button that
will although "paging" to additional sets of six jumbo buttons. But the
logic will
be the same for each page -- takes two discrete touches/clicks with
unlimmited
time inbetween -- to trigger the buttons action. The default icon will
show --
when the first click is made this icon is inverted. Check the attached
mpc.h and mpc.cpp (mpc is short for project MomPC).
BOOL C_tst_04_Dlg::OnInitDialog()
{ . . .
HWND DlgH = GetSafeHwnd();
gMBs.do_mpc_btn_init( DlgH ); // do the MPC button
initialization, bitmaps, counts, states, etc.
****
I do not understand any of this. If you want special button behavior, you
don't generate
some *random* class (I note that you have never once shown the declaration
of gMBs,
whatever that is...), you generate a *derived* class of CButton, and do
all the work
there! Then there is no need for the totally random class to access any
control; the work
is done in the button, where it belongs.
For example, check out my "Better Bitmap Button" class on my MVP Tips
site, which shows
how to create a bitmap button, and how to create a toggling button. You
are putting
button display logic in a random class that has nothing to do with
buttons, and that is
the source of all your problems. Get rid of this class, and derive a
class from CButton.
Suppose you call it
CMyButton
then you will have a MyButton.h and MyButton.cpp file created for you. Go
into
MyButton.cpp, find the offending #include of the project file, and replace
it with
#include "resource.h". Then make it an "owner draw" button and do a
DrawItem handler for
it that paints it in the appropriate fashion.
You can use my Better Bitmap Button code as a starting point to make it do
whatever you
want it to do. But do not use auxiliary classes for this purpose.
****
. . . }
The tasks being done but these jumbo buttons is quite varied -- it seemed
to be in good coding practices to isolate the button and screen of buttons
logic and processing, no? But what worked fine inside of
C_tst_04_Dlg::OnInitDialog() is not working within
gMBs.do_mpc_btn_init( )?
****
That's because your whole approach is flawed; redo as suggested above. It
is not
*supposed* to work in do_mpc_btn_init, it shouldn't, and attempting to
kludge up some
solution that passes the HWND into this class is erroneous. Use a derived
class.
Note you will have to hand-edit your .h file to say
CMyButton m_ButtonWithReasonableName;
from its original declaration of
CButton m_ButtonWithReasonableName;
but that's trivial editing.
Read my essays on dialog boxes on my MVP Tips site.
joe
****
Do I explain this well enough?
Thanks again.
Sincerely,
Kevin Waite
"Giovanni Dicanio" <giovanniDOTdicanio@REMOVEMEgmail.com> wrote in message
news:e6tdbk1tJHA.5664@TK2MSFTNGP03.phx.gbl...
"Kevin Waite" <kevin001.waite@gmail.com> ha scritto nel messaggio
news:D01FE180-0B2B-47F0-B614-FE4003566E58@microsoft.com...
Newbie here -- in my default wizard MFC Dlg.cpp -- I can use GetDlgItem
with a single parm, say the ID of a button -- and it works great -- in
fact both decls are present -- the single parm
ID and the ( HWND hdle, ID ) ......
When I make a new class module -- xxx.cpp --- and include exactly the
same includes from Dlg.cpp -- exactly the same!
I don't get the single parm GetDlgItem( ID ) -- booo -- I only get the
2
parm (HWND, ID) ver . . . . rats rats rats
I think that with "single param ID" GetDlgItem() you mean the member
function of CWnd class:
http://msdn.microsoft.com/en-us/library/77d16yhw.aspx
CWnd* CWnd::GetDlgItem(
int nID
) const;
and with "the 2 parm (HWND, ID) ver" you mean the global Win32 API
function ::GetDlgItem:
http://msdn.microsoft.com/en-us/library/ms645481.aspx
HWND GetDlgItem(
HWND hDlg,
int nIDDlgItem
);
The first parameter 'HWND' in the member function version (the "single
param version") is implicit, because the HWND used is the one associated
to the particular instance of CWnd (your CDialog-derived class).
Instead, in the global function you must specify the handle of the
dialog-box you want to apply GetDlgItem to.
So -- either solution would be great --
a) how to get the single parm version of GetDlgItem vialbe from xxx.cpp
In general, in an MFC app, it would make sense to call GetDlgItem member
function within the CDialog-derived class. Why do you need the global
::GetDlgItem function?
Could you please post some code?
b) or how to querry the Dialog Handle in the form of HWND
In MFC, if you want to get the HWND associated to some CWnd (or derived)
class, you can use CWnd::GetSafeHwnd() method.
But I'm not sure if your design is good. If you post some code, I think
we
could give better advice.
Note also that in MFC apps it would make more sense to add member
variables to CDialog-derived classes associated to controls (e.g.
CListBox
m_myListBox), instead of calling GetDlgItem() method and cast the
returned
CWnd pointer to some control class (e.g. CListBox * pListBox = (CListBox
*)GetDlgItem(IDC_MYLISTBOX)).
HTH,
Giovanni
Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm