PostMessage... GetMessage???

Posted on 2000-03-07
Medium Priority
Last Modified: 2006-11-17
I want the new instance of an app to send a message to the old one.

For example I start MyProg by clicking "first.txt". After that I click on "second.txt" and I want the new MyProg to do something like :

PostMessage(oldMyProgHandle, WM_COMMAND, 0&, "second.txt")

But how do I Get the message ??
Question by:HellSlayer
LVL 14

Expert Comment

ID: 2594268
You need to create a message handler (windows hook) See the following microsoft KB articles:

HOWTO: Build a Windows Message Handler with AddressOf in VB

HOWTO: Pass String Data Between Applications Using SendMessage

HOWTO: Hook Into a Window's Messages Using AddressOf


LVL 32

Accepted Solution

Erick37 earned 280 total points
ID: 2594281
If you are trying to open associated files with one instance of your program, use DDE.  This sample code will populate a listbox with filenames as you double click the associated file.

Place Label1 and List1 on Form1:

Option Explicit

Private Sub Form_Load()
    ' At design time set Form's LinkMode property = 1 (Source)
    If App.PrevInstance Then
        On Error Resume Next
        Label1.LinkTopic = App.EXEName & "|cmdLine"
        Label1.LinkItem = ""
        Label1.LinkMode = vbLinkManual
        Label1.LinkExecute Command
        If Err Then
            MsgBox Err.Description, vbOKOnly, "Error " & CStr(Err.Number)
            Unload Me
            Exit Sub
        End If
    End If
    'First instance:
    Label1.Visible = False
    List1.AddItem Command
    Me.LinkTopic = "cmdLine" ' wait for "cmdLine" links
End Sub

Private Sub Form_LinkExecute(CmdStr As String, Cancel As Integer)
    'Command lines from other instances
    'will be passed thru CmdString
    List1.AddItem CmdStr
    Cancel = False
End Sub

Private Sub Form_Terminate()
End Sub

Author Comment

ID: 2602685
Really cool sample without any API !!!

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