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Hi everybody
I want my application to be started only 1 time.
If the user launch again the executable, it activates the application already opened and do not open a second application...
How can I do that??
Specification of the project?
Test if this process already exists in the machine
at the launch of the app??
Fzz
You can use the '.PrevInstance' property of the 'App' object at runtime to see if an instance of your program is already running.
eg.
If App.PrevInstance then
End ' or Unload me etc
End If
If you want a more detailed explanation and to see how to copy data between a newly started instance and an existing instance, take a look at :
http://codeguru.developer.com/vb/articles/1804.shtml
Chris Eastwood
CodeGuru - the website for developers
http://codeguru.developer.com/vb
Add the following code to your MainForm_Initialize() subroutine
' Checks if the Application is already running
If (App.PrevInstance = True) Then End
Good Luck!
for some reason that doesn;t work
I'd be interested to see how you're testing it - the App.PrevInstance will only be true at run-time when you already have an instance of your program running (you can't test it from the IDE because VB only allows one copy of a project open at a time).
Chris Eastwood
CodeGuru - the website for developers
http://codeguru.developer.com/vb
Component that uses App.PrevInstance can cause problems in Win NT
A computer running Windows NT can support multiple desktops. When you're using a component designed to work with distributed COM, this can result in the following scenario:
· A client program in a user desktop requests one of the objects the component provides. Because the component is physically located on the same machine, the component is started in the user desktop.
· Subsequently, a client program on another computer uses distributed COM to request one of the objects the component provides. A second instance of the component is started, in a system desktop.
There are now two instances of the component running on the same NT computer, in different desktops.
This scenario is not a problem, unless the author of the component has placed a test for App.PrevInstance in the startup code for the component, to prevent multiple copies of the component from running on the same computer. In this case, the remote object creation will fail.
So try to check the App.PrevInstance in Win 95/98.
Good Luck!
I need your help. I knew I could check if the app was already running using App.PrevInstance, but my problem is slightly different. I want to know how to pass command line arguments from the latest opened instance to the previous one (i.e. if my program opens files, I want all files to be opened in the same window). Have I to use DDE or something similar?
Thanks in advance
Place this code into form_load
If App.PrevInstance = true then
End
End If
That code goes into Form_Load()
and to test it, ss Chris already said, you need to make an .exe and try to run it twice
You have some different ways to do it. The easiest one is to save all the arguments into a new ASCII text file, which after that your second application can read. If you don't like it, try API Function
Send_Message(), but don't forget about syncronization, if your first application is still not running, and
you already trying to send the message to it from the second application, you'll have a problem. File is
also good when you want to share data between Windows and DOS applications. Anyway, good luck!
Really thanks! But if I create a text file, the existing instance has to repeatedly check if this file exists or has been updated, hasn't it?
Er... I'm a total learner about API, can you at least tell me how works Send_Message()?
Sorry if I bother you again, and thanks in advance!
I am sending you the link of good enough example of SendMessage() function:
http://www.vbgreatone.8m.com/VB/s/sendmessage.htm
Good Luck!
Well that is definitely a very interesting question!
Best Regards ;-)
Really thanks!!! The API guide I was looking for!!!