asked on

File association, open only one instance of file

Hey Experts
I am working on an app that is run via file associations. I need to only have one instance running, but change the loaded file when it is double clicked. I have the code for the single instance, but it does not change the loaded file. I was wondering how this is accomplished.

Here is the code I have:

FORM1---------------------------------------------------------------------------------------------------------------------------------------
Private Sub Form_Load()
'test code
If App.PrevInstance Then
ActivatePrevInstance
End If
'end test code
On Error GoTo Form_Err

Dim strFilename As String
Dim iFileNumber As Integer

strFilename = Replace$(Command$, Chr$(34), vbNullString)
If strFilename <> vbNullString Then
If Dir$(strFilename) <> vbNullString Then
iFileNumber = FreeFile()
Open strFilename For Input As #iFileNumber
RichText1.Text = Input$(LOF(iFileNumber), #iFileNumber)
Close #iFileNumber
End If
End If
Form_Err:
MsgBox "Error " & Err.Number & Err.Description & vbNewLine & strFilename
End Sub
------------------------------------------------------------------------------------------------------------------

MODULE1---------------------------------------------------------------------------------------------------------

Option Explicit

Public Const GW_HWNDPREV = 3
Declare Function OpenIcon Lib "user32" (ByVal hwnd As Long) As Long
Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Declare Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long
Declare Function SetForegroundWindow Lib "user32" (ByVal hwnd As Long) As Long

Sub ActivatePrevInstance()

Dim OldTitle As String
Dim PrevHndl As Long
Dim result As Long

'Save the title of the application.
OldTitle = App.Title

'Rename the title of this application so FindWindow
'will not find this application instance.
App.Title = "unwanted instance"

'Attempt to get window handle using VB6 class name
PrevHndl = FindWindow("ThunderRT6Main", OldTitle)

'Check if found
If PrevHndl = 0 Then
'No previous instance found.
Exit Sub
End If

'Get handle to previous window.
PrevHndl = GetWindow(PrevHndl, GW_HWNDPREV)

'Restore the program.
result = OpenIcon(PrevHndl)

'Activate the application.
result = SetForegroundWindow(PrevHndl)

'End the application.
End

End Sub
---------------------------------------------------------------------------------------------------------------------------

thanks
-Bob

Erick37

This article demonstrates how to register associations and an easy-to-use module which can pass any parameters to an existing instance of your application.

http://www.vbaccelerator.com/home/VB/Code/Libraries/Shell_Projects/Registering_File_Associations/article.asp

codeconqueror

The problem is that your killing the instance that got the new file name without passing the file name over to the other instance.

Instead of activating the other instance, do this:

Add the following to your declarations:
Const WM_QUIT = &H12
Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

Then call it using:

SendMessage PrevHndl, WM_QUIT, 0&, 0&

Here is the updated code:

<CODE SNIPPET>
Private Sub Form_Load()
'test code
If App.PrevInstance Then
KillPrevInstance
End If
'end test code
On Error GoTo Form_Err

Dim strFilename As String
Dim iFileNumber As Integer

strFilename = Replace$(Command$, Chr$(34), vbNullString)
If strFilename <> vbNullString Then
If Dir$(strFilename) <> vbNullString Then
iFileNumber = FreeFile()
Open strFilename For Input As #iFileNumber
RichText1.Text = Input$(LOF(iFileNumber), #iFileNumber)
Close #iFileNumber
End If
Me.Show
Else
Unload Me
End If
Exit Sub
Form_Err:
MsgBox "Error " & Err.Number & Err.Description & vbNewLine & strFilename
End Sub
</CODE SNIPPET>

Here's the module code:

<CODE SNIPPET>
Option Explicit

Public Const GW_HWNDPREV = 3
Const WM_QUIT = &H12
Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Declare Function OpenIcon Lib "user32" (ByVal hwnd As Long) As Long
Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Declare Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long
Declare Function SetForegroundWindow Lib "user32" (ByVal hwnd As Long) As Long

Sub ActivatePrevInstance()

Dim OldTitle As String
Dim PrevHndl As Long
Dim result As Long

'Save the title of the application.
OldTitle = App.Title

'Rename the title of this application so FindWindow
'will not find this application instance.
App.Title = "unwanted instance"

'Attempt to get window handle using VB6 class name
PrevHndl = FindWindow("ThunderRT6Main", OldTitle)

'Check if found
If PrevHndl = 0 Then
'No previous instance found.
Exit Sub
End If

'Get handle to previous window.
PrevHndl = GetWindow(PrevHndl, GW_HWNDPREV)
SendMessage PrevHndl, WM_QUIT, 0&, 0& '*** Tell the other instance to shut down
App.Title = OldTitle
End Sub
</CODE SNIPPET>

codeconqueror

Woops, forgot to change the name of the sub to:

Sub KillPrevInstance

codeconqueror

Here is the complete corrected code:

<CODE SNIPPET>
Private Sub Form_Load()
If App.PrevInstance Then
KillPrevInstance
End If

On Error GoTo Form_Err

Dim strFilename As String
Dim iFileNumber As Integer

strFilename = Replace$(Command$, Chr$(34), vbNullString)
If Lenb(strFilename) > 0 Then
If Lenb(Dir$(strFilename)) > 0 Then
iFileNumber = FreeFile
Open strFilename For Input As #iFileNumber
RichText1.Text = Input$(LOF(iFileNumber), #iFileNumber)
Close #iFileNumber
End If
Me.Show
Else
Unload Me
End If
Exit Sub

Form_Err:
MsgBox "Error " & Err.Number & ": " & Err.Description & vbNewLine & "File Requested: " & strFilename
End Sub
</CODE SNIPPET>

Here's the module code:

<CODE SNIPPET>
Option Explicit

Public Const GW_HWNDPREV = 3
Const WM_QUIT = &H12
Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Declare Function OpenIcon Lib "user32" (ByVal hwnd As Long) As Long
Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Declare Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long
Declare Function SetForegroundWindow Lib "user32" (ByVal hwnd As Long) As Long

Public Function KillPrevInstance()

Dim OldTitle As String
Dim PrevHndl As Long
Dim result As Long

'Save the title of the application.
OldTitle = App.Title

'Rename the title of this application so FindWindow
'will not find this application instance.
App.Title = "unwanted instance"

'Attempt to get window handle using VB6 class name
PrevHndl = FindWindow("ThunderRT6Main", OldTitle)

'Check if found
If PrevHndl = 0 Then
'No previous instance found.
Exit Sub
End If

'Get handle to previous window.
PrevHndl = GetWindow(PrevHndl, GW_HWNDPREV)
SendMessage PrevHndl, WM_QUIT, 0&, 0& '*** Tell the other instance to shut down
App.Title = OldTitle
End Function
</CODE SNIPPET>

astrohelp

ASKER

Hey CC, thanks for the code, but it is not closing the previous instance...

astrohelp

ASKER

any thoughts?

codeconqueror

Here is updated module code, should work:

<CODE SNIPPET>
Option Explicit

Public Const GW_HWNDPREV = 3
Const WM_QUIT = &H12
Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Declare Function OpenIcon Lib "user32" (ByVal hwnd As Long) As Long
Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Declare Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long
Declare Function SetForegroundWindow Lib "user32" (ByVal hwnd As Long) As Long

Public Function KillPrevInstance()

Dim OldTitle As String
Dim PrevHndl As Long
Dim result As Long

'Save the title of the application.
OldTitle = App.Title

'Rename the title of this application so FindWindow
'will not find this application instance.
App.Title = "Wanted Instance"

'Attempt to get window handle using VB6 class name
PrevHndl = FindWindow("ThunderRT6Main", OldTitle) '**** You may want to try passing the caption of the other instance instead if this doesn't find it

If PrevHndl <> 0 Then
SendMessage PrevHndl, WM_QUIT, 0&, 0& '*** Tell the other instance to shut down
End If

App.Title = OldTitle
End Function
</CODE SNIPPET>

Erick37

Still need help on this Astrohelp?

astrohelp

ASKER

Yes please Erick37, none of the previous suggestions have worked. If you have a solution, please let me know.

thanks

ASKER CERTIFIED SOLUTION

Erick37

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GPrentice00

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