PostMessage from WorkerThread to Main Window in MFC
CMFC_TestApplicationDlg::OnBnClickedMfcbutton1()
may return before the thread starts. This causes your ThreadParams
to go out of scope, so when you access it from the thread, you are accessing freed memory. You need to allocate it some other way, such as:
void CMFC_TestApplicationDlg::OnBnClickedMfcbutton1()
{
ThreadParams* params = new ThreadParams();
params->m_hWnd = m_hWnd;
params->FTPHost = "test_host";
params->FTPUsername = "test";
params->FTPPassword = "test";
AfxBeginThread(FTPConnectThread,params);
}
//child thread function
UINT FTPConnectThread( LPVOID pParam )
{
if(pParam == NULL)
{
return 0;
}
ThreadParams *params = (ThreadParams*)pParam;
OutputDebugString(params->FTPHost);
Sleep(4000); //simulating a network call
CString * message = new CString("Conencted");
PostMessage(params->m_hWnd,FTP_APP_STATUS_UPDATE,0,(LPARAM)message);
delete params;
return 1;
}
Comments
-
Muhammad Ummar almost 2 years
I have a MFC application, which has a worker thread, what I want to do is to post message from worker thread to the Main GUI thread to update some status messages on GUI. What I have done so far is
Registered a new window message
//custom messages static UINT FTP_APP_STATUS_UPDATE = ::RegisterWindowMessageA("FTP_APP_STATUS_UPDATE");
Added this message to the message map of dialog class
ON_MESSAGE(FTP_APP_STATUS_UPDATE, &CMFC_TestApplicationDlg::OnStatusUpdate)
The prototype of
OnStatusUpdate
isafx_msg LRESULT OnStatusUpdate(WPARAM, LPARAM);
and definition is
LRESULT CMFC_TestApplicationDlg::OnStatusUpdate(WPARAM wParam, LPARAM lParam) { //This function is not called at all. return 0; }
and the worker thread calling code is
void CMFC_TestApplicationDlg::OnBnClickedMfcbutton1() { ThreadParams params; params.m_hWnd = m_hWnd; params.FTPHost = "test_host"; params.FTPUsername = "test"; params.FTPPassword = "test"; AfxBeginThread(FTPConnectThread,¶ms); }
and Worker thread code is
//child thread function UINT FTPConnectThread( LPVOID pParam ) { if(pParam == NULL) { return 0; } ThreadParams *params = (ThreadParams*)pParam; OutputDebugString(params->FTPHost); Sleep(4000); //simulating a network call CString * message = new CString("Conencted"); PostMessage(params->m_hWnd,FTP_APP_STATUS_UPDATE,0,(LPARAM)message); //PostMessage do nothing? what I am doing wrong? return 1; }
the problem is when the PostMessage function is called the
OnStatusUpdate
should be called, but it is not being called, no exception or assertion is thrown, What I am doing wrong? I have triedON_REGISTERED_MESSAGE
andON_MESSAGE
but no success, any help?