Solved

Accessing view object from launched thread

Posted on 1997-11-21
2
362 Views
Last Modified: 2013-11-20
I am having trouble getting a copy of my CListView derived view from within a worker thread I launch from the view. I understand that one should not pass MFC objects to threads, so I am passing the handle to the view and trying to get access to the view via the FromHandlePermanent function but the call returns NULL.

Can anyone determine where I am going wrong here?
---------------------------------------------------------------------------------
- from my CListView derived view class I launch the thread

AfxBeginThread(LoadThreadProc, m_hWnd);

---------------------------------------------------------------------------------
- here is the thread
UINT LoadThreadProc( LPVOID pParam )
{
    HWND hWndView = (HWND)pParam;
   
    CMyListView* pView = (CMyListView*)
        CWnd::FromHandlePermanent(hWndView);
      

    if (pView == NULL ||
        !pView->IsKindOf(RUNTIME_CLASS(CMyListView)))
    return (UINT)-1;    // illegal parameter


    return 0;    // thread completed successfully
}
0
Comment
Question by:rascal
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 15

Accepted Solution

by:
Tommy Hui earned 20 total points
ID: 1310517
Why not send the view a message with SendMessage? That's what I'm currently doing. Anything else and you're going to run into assertions with MFC because it really isn't designed for that.
0
 
LVL 3

Expert Comment

by:shaig
ID: 1310518
That's right.  MFC code is not thread safe,
FromHandlePermanent probably works only on the current thread, but it realy doesn't matter because:
Creating or getting a CWnd for a window that is manipulated by a different thread is dangoures!  even a simple thing as reading the window's caption can cause your application to crush - if one thread reads and another writes!
Only the message queqe is protected via a semaphore, thats why you want to send messages ( preffers that carry dynamicly allocated data ).  if your code can be async. then it's even better to use the PostMessage().
0

Featured Post

Want Experts Exchange at your fingertips?

With Experts Exchange’s latest app release, you can now experience our most recent features, updates, and the same community interface while on-the-go. Download our latest app release at the Android or Apple stores today!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction: Dialogs (2) modeless dialog and a worker thread.  Handling data shared between threads.  Recursive functions. Continuing from the tenth article about sudoku.   Last article we worked with a modal dialog to help maintain informat…
If you use Adobe Reader X it is possible you can't open OLE PDF documents in the standard. The reason is the 'save box mode' in adobe reader X. Many people think the protected Mode of adobe reader x is only to stop the write access. But this fe…
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
In this video, viewers will be given step by step instructions on adjusting mouse, pointer and cursor visibility in Microsoft Windows 10. The video seeks to educate those who are struggling with the new Windows 10 Graphical User Interface. Change Cu…
Suggested Courses

636 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question