Click here to Skip to main content
11,495,371 members (61,985 online)
Rate this: bad
Please Sign up or sign in to vote.
See more: VS2005 dialog VC++ event
I have one issue regarding to the dialog box. I have one menu, after clicked on this a dialog is popped up. When I clicked again on the same menu without closing the last opened dialog an another instance of same dialog is opened. This happens till I close all the created instance of the dialog. How I found that the dialog's instance is already run or not or how to detect that the dialog is opened or not? Please somebody help me
Posted 11-Oct-12 21:44pm
Wes Aday at 12-Oct-12 7:47am
Simple, show the dialog modal then you will not have this problem.
Rate this: bad
Please Sign up or sign in to vote.

Solution 1

Use FindWindow() to get handle to your window.

HWND hDlgExists = ::FindWindow(0,”MyDialogTitle”); // hDlgExists will be NULL if dlg is not exist.
vaibhavj_navdurga at 12-Oct-12 3:09am
I used this but in future if the name of the dialog is changed then this method is not useful. Is there any another way in which I pass the handle of that dialog and then it detect that this dialog is opened or not?
Santhosh_G at 12-Oct-12 3:32am
// The handle to be tested.
HWND hWindow = GetSafeHwnd();

// Check whether the window is still there.
BOOL bWindowAlive = IsWindow( hWindow );
vaibhavj_navdurga at 12-Oct-12 4:05am
I got the handle of the dialog as null. How I get the handle of the window? I used the below code:

void CVTXMIOCaptureDlg::OnContextViewsetup()
CEngineSetupDialog *dlg = new CEngineSetupDialog();
HWND hWindow = dlg->GetSafeHwnd();
BOOL bWndAlive = ::IsWindow(hWindow);
Santhosh_G at 12-Oct-12 6:14am
Simply creating a CDialog instance will not give a valid window handle.
TestDlg* pDlg = new TestDlg();
HWND hNullHandle = pDlg->GetSafeHwnd(); // Handle will be NULL
pDlg->Create( IDD_DIALOG_ID, 0 );
HWND hValidaHandle = pDlg->GetSafeHwnd(); // Handle will be Valid
pDlg->ShowWindow( SW_SHOW );
Santhosh_G at 12-Oct-12 5:36am
If it is DoModal() to display the dialog, how you will get more than one dialog ?
Are you creating new process, or new thread to display new dialog ?
vaibhavj_navdurga at 12-Oct-12 7:15am
No, I can't use or create any process or thread. It is just simple dialog whenever user select the menu it shows that dialog. It is DoModal(), but whenever I click on the menu it creates the new one dialog which is wrong. This menu item is handled from a tray icon, that's why user select that menu item again and again and the new dialog instance get created. How to resolved it please tell me.
Rate this: bad
Please Sign up or sign in to vote.

Solution 2

bool bAlreadyRunning;
HANDLE hMutexOneInstance = ::CreateMutex( NULL, FALSE, _T("Your_Dialog_Name"));
bAlreadyRunning = ( ::GetLastError() == ERROR_ALREADY_EXISTS ||
                    ::GetLastError() == ERROR_ACCESS_DENIED);
if( !bAlreadyRunning )
  // Initialize Dialog and Call DoModal()
vaibhavj_navdurga at 12-Oct-12 8:12am
instead of using mutex I directly used FindWindow() method because both are used the Name of the dialog instead of Handle.
Santhosh_G at 12-Oct-12 8:22am
Its not required to have the same name of Dialog name.
Any unique name to indicate your dialog. It should be unique. If anyone else opened a mutex with same name, your dialog will not appear.
vaibhavj_navdurga at 12-Oct-12 8:33am
I used the above code it creates an issue: As first time it creates the window then if I again select the menu it didn't allow to create dialog again. But if I selects the Apply or Cancel button, the dialog closed and after that I select the menu then it didn't allow to create the dialog. It happens till I exit the tray icon. When I start the application again it work and did the same thing as I above explained.
Santhosh_G at 12-Oct-12 8:48am
After DoModal(), please call ReleaseMutex() and CloseHandle() to close the mutex instance.
vaibhavj_navdurga at 12-Oct-12 9:15am
Thanx for your help

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

  Print Answers RSS
0 Dnyaneshwar@Pune 692
1 CHill60 318
2 Sascha Lefèvre 275
3 Sergey Alexandrovich Kryukov 255
4 Nakul Chaudhari 236
0 Sergey Alexandrovich Kryukov 10,307
1 OriginalGriff 8,821
2 Sascha Lefèvre 3,889
3 Maciej Los 3,412
4 Richard Deeming 2,560

Advertise | Privacy | Mobile
Web02 | 2.8.150520.1 | Last Updated 12 Oct 2012
Copyright © CodeProject, 1999-2015
All Rights Reserved. Terms of Service
Layout: fixed | fluid

CodeProject, 503-250 Ferrand Drive Toronto Ontario, M3C 3G8 Canada +1 416-849-8900 x 100