ID Number: Q72918
1.00
WINDOWS
Summary:
To determine if a specific program is running, call the Windows API
function FindWindow. FindWindow returns the handle of the window whose
class is given by the lpClassname parameter and whose window name, or
caption, is given by the lpCaption parameter. If the returned value is
zero, the application is not running.
This information applies to Microsoft Visual Basic Programming System
version 1.0 for Windows.
More Information:
By calling FindWindow with a combination of a specific program's class
name and/or the title bar caption, your program can determine whether
that specific program is running.
When an application is started from the Program Manager, it registers
the class name of the form. The window class provides information
about the name, attributes, and resources required by your form. All
Visual Basic forms have a class name of "ThunderForm." You can
determine the class name of an application by using SPY.EXE that comes
with the Microsoft Windows 3.0 Software Development Kit (SDK).
If the window has a caption bar title, you can also use the title to
locate the instance of the running application. This caption text is
valid even when the application is minimized to an icon.
Because another instance of your Visual Basic program will have the
same class name and may have the same title bar caption, you must use
dynamic data exchange (DDE) to determine if another instance of your
Visual Basic program is running. (This DDE technique is not shown in
this article).
The following example shows three ways to determine if the Windows 3.0
Calculator is running. To create the program, do the following:
1. Create a form.
2. Declare the Windows 3.0 API function FindWindow in the Global-
Declarations section of the code window. The variables are declared
as "Any" because you can pass either a pointer to a string, or a NULL
value. You as a programmer are responsible for passing the correct
variable type. Note that the Declare statement should be entered on
just one line:
Declare Function FindWindow% Lib "user" (ByVal lpClassName As Any,
ByVal lpCaption As Any)
3. Add the following code to the form's Click event. This example
demonstrates how you can find the instance of the application with a
combination of the class name and/or the window's caption. In this
example, the application will find an instance of the Windows 3.0
calculator (CALC.EXE).
Sub Form_Click ()
Const NULL = 0&
lpClassName$ = "SciCalc"
lpCaption$ = "Calculator"
Print "Handle = ";FindWindow(lpClassName$, NULL)
Print "Handle = ";FindWindow(NULL, lpCaption$)
Print "Handle = ";FindWindow(lpClassName$,lpCaption$)
End Sub
4. Run this program with CALC.EXE running and without CALC.EXE
running. If CALC.EXE is running, your application will print an
arbitrary handle. If CALC.EXE is not running, your application will
print the number zero as a handle.
Below are some class names of applications that are shipped with
Windows 3.0:
Class Name Application
----------- -----------
SciCalc CALC.EXE
CalWndMain CALENDAR.EXE
Cardfile CARDFILE.EXE
Clipboard CLIPBOARD.EXE
Clock CLOCK.EXE
CtlPanelClass CONTROL.EXE
XLMain EXCEL.EXE
Session MS-DOS.EXE
Notepad NOTE.EXE
pbParent PBRUSH.EXE
Pif PIFEDIT.EXE
PrintManager PRINTMAN.EXE
Progman PROGMAN.EXE (Windows Program manager)
Recorder RECORDER.EXE
Reversi REVERSI.EXE
#32770 SETUP.EXE
Solitaire SOL.EXE
Terminal TERMINAL.EXE
WFS_Frame WINFILE.EXE
MW_WINHELP WINHELP.EXE
#32770 WINVER.EXE
OpusApp WINWORD.EXE
MSWRITE_MENU WRITE.EXE
Reference(s):
"Programming Windows: the Microsoft Guide to Writing Applications
for Windows 3," Charles Petzold. Microsoft Press, 1990.
"Peter Norton's Windows 3.0 Power Programming Techniques," Peter
Norton and Paul Yao. Bantam Computer Books, 1990.
"Microsoft Windows 3.0 Software Development Kit: Reference Volume 1."
WINSDK.HLP file shipped with Microsoft Windows 3.0 SDK.
Additional reference words: 1.00 3.00