Set unsigned character value to CString type edit control in mfc

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In my MFC dialogue based application, I want to Read data through serial port and whatever data received from that,displayed into Edit control,but somehow it is not working,as I used below methodology:

C#

/*CString msg;
    msg.Format(L"%c",Buff);*/
    //strcpy( (char*)Buff,ThreadStruct->m_handleDlg->m_console);//"Hello World");
    while(1)
    {
        ReadFile(DeviceHandle,&Buff,1,&WriteBytes,NULL);
        //ThreadStruct->m_handleDlg->m_OutConsole.ReplaceSel(L"\r\n\r\n\r"+msg+L"\r\n\r\n\r");
        //ThreadStruct->m_handleDlg->m_OutConsole.SetWindowTextW(Buff);
        //ThreadStruct->m_handleDlg->m_console.Format(L"%uc",Buff);
    }

for above code I used worker thread.So that used ThreadStruct.
above no one is running,gives error! How to do that?

Posted 18-Jun-13 4:38am

Venkat Raghvan

Updated 18-Jun-13 4:40am

v2

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Nelek 18-Jun-13 10:42am

Which error? Where is he complaining? It may happen, that the problem is somewhere totally different. Can you use the "improve question" widget and elaborate a bit more?

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Jochen Arndt · Accepted Answer · 2013-06-18T06:18:00

Solution 1

You are reading a single character (byte) into Buff. So you can't pass Buff where a NULL terminated string parameter is expected without appending the NULL terminator. Your code snippet indicates also that you are using a Unicode build. So the characters read from the serial port must be converted to Unicode. Using a CString, this can be done this way (when the received characters are plain ASCII or from the ANSI code page of your system):

C++

CString msg;
// Format single ASCII/ANSI char
msg.Format(L"%hc", Buff[0]);
// Format ASCII/ANSI string after appending a NULL char
Buff[1] = 0;
msg.Format(L"%hs", Buff);

The h prefix tells the format function that the parameter is an ASCII/ANSI char or string and performs the conversion to Unicode.

Posted 18-Jun-13 6:18am

Jochen Arndt

Comments

Venkat Raghvan 25-Jun-13 9:45am

it not gives error,but how to insert that Buff value to edit control?
If I used SetWindowText(),it gives run time error?

Jochen Arndt 25-Jun-13 11:54am

If you have created the CString like in my example, use
EditCtrl.SetWindowText(msg.GetString());

Your problem is not passing unsigned char[*] to char[*) (you can just pass such as is using casting if necessary), but passing char[*] to WCHAR[*]. Your received data are unsigned char, but SetWindowText() requires a LPCWSTR (const WCHAR *) with Unicode builds. So the data must be converted from char to WCHAR.

Regarding the unsigned:
You may declare your Buff variable as char rather than unsigned char. There is no need to use unsigned char in the code shown by you.

Venkat Raghvan 26-Jun-13 2:50am

I do whatever you said,but it does not run safely,it breaks at run time.
I tried with typecasting also,but it failed at run time.

Jochen Arndt 26-Jun-13 3:32am

Sorry, I missed one thing when writing the above comment:
You are trying to update the text of a control which belongs to another thread. Then you must send a WM_SETTEXT message rather than using SetWindowText().

If you need more complex operations like inserting text, you must use some kind of signaling. One option is using user defined messages:
- The worker thread sends a user defined message when new data are available.
- The main thread handles this message and performs the operation on the edit control.

When passing a single char, this can be done using the LPARAM or WPARAM parameter of SendMessage(). When passing a string, this can be done passing a pointer to dynamically allocated memory which must be freed by the recipient of the message or storing the string in a member variable of the worker thread and providing a function that copies the data from the member variable to a destination buffer (which requires some kind of locking).

This link may be helpful: http://www.codeproject.com/Articles/552/Using-Worker-Threads (see the 'Worker threads and the GUI II: Don't touch the GUI' section).

Venkat Raghvan 26-Jun-13 6:07am

ok,but how to pass WM_SETTEXT message to control? I declared in message map section;it gives error!

Jochen Arndt 26-Jun-13 10:43am

Not passing, sending:
::SendMessage(hWnd, WM_SETTEXT, NULL, (LPARAM)lpszMsg);
where hWnd is the HWND of the control and lpszMsg is the NULL terminated string (LPCWSTR with Unicode builds and LPCSTR with multi byte builds).

The link from previous comment is missing: http://www.codeproject.com/Articles/552/Using-Worker-Threads.

Venkat Raghvan 27-Jun-13 1:22am

Ok,Thank you,it not returned at run time now!!

Venkat Raghvan 1-Jul-13 6:07am

whenever I passed Character 'b' to Edit control it always shows some anonymous values like `s`.I don't get resulted character 'b'

Jochen Arndt 1-Jul-13 6:16am

How did you pass the char?

Venkat Raghvan 1-Jul-13 6:25am

msg.Format(L"%c",ReadChar[0]);
::SendMessageA(hwnd_Console,WM_SETTEXT,NULL,(LPARAM)&msg);

Jochen Arndt 1-Jul-13 6:47am

I still assume that you are using a Unicode build (indicated by using the wide format string L"%c"). If so, you must use SendMessageW instead of SendMessageA (or better just SendMessage; the compiler will insert the correct version according to the project settings).

If ReadChar[] is of type char[], you should use the format string L"%hc" (or better _T("%hc") ) to indicate that you want to print a char instead of a WCHAR. However, when ReadChar[0] is a 7-bit ASCII character, the result is the same.

When msg is of type CString, you should use msg.GetString() or the CString PCXSTR operator to get a pointer to the string:
SendMessage(hwnd_Console, WM_SETTEXT, NULL, (LPARAM)msg.GetString());
or
SendMessage(hwnd_Console, WM_SETTEXT, NULL, (LPARAM)(LPCTSTR)msg);

Venkat Raghvan 1-Jul-13 7:14am

Sorry! I was using wrong methodology!Now it works fine!!