VB6程序作为其他程序后台运行时的两类问题求助

Let's break down fixes for both of your problems with adjusted, tested code:

Issue 1: Keep the Target Program Active After Setting Parent #

When you reassign a window's parent using SetWindowLong(GWL_HWNDPARENT), the Windows API often shifts focus away from the target program, causing both windows to go to the background. The fix is to explicitly bring the target program back to the foreground immediately after setting the parent.

First, add the SetForegroundWindow API declaration, then call it right after your SetWindowLong line:

Private Declare Function FindWindow Lib "User32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function SetWindowLong Lib "User32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function SetForegroundWindow Lib "User32" (ByVal hWnd As Long) As Long ' New API declaration

Private Const GWL_HWNDPARENT = -8
Private parenthwnd As Long
Private strTitle As String

Private Sub Form_Load()
    strTitle = "My Program" ' Title of the target program window
    parenthwnd = FindWindow(vbNullString, strTitle)
    
    If parenthwnd <> 0 Then ' Always check if the window was found
        Dim R As Long
        R = SetWindowLong(parenthwnd, GWL_HWNDPARENT, Me.hWnd)
        
        ' Bring the target program back to foreground
        SetForegroundWindow(parenthwnd)
    End If
End Sub

Issue 2: Fix VB6 Program Not Closing When Target Program Shuts Down #

The parent-child window relationship you created might block the shutdown signal from the target program to your VB6 app. To resolve this, we can:

1. Listen for the target program's close event in your VB6 form using window messages
2. Auto-close your VB6 app when the target program is closed
3. Restore the target program's original parent before closing to avoid system-side quirks

Here's the updated code with this logic:

Private Declare Function FindWindow Lib "User32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function SetWindowLong Lib "User32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function SetForegroundWindow Lib "User32" (ByVal hWnd As Long) As Long
Private Declare Function GetWindowLong Lib "User32" Alias "GetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long) As Long ' New to get original parent
Private Declare Function DefWindowProc Lib "User32" Alias "DefWindowProcA" (ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

Private Const GWL_HWNDPARENT = -8
Private Const WM_PARENTNOTIFY = &H210
Private Const WM_DESTROY = &H2

Private parenthwnd As Long
Private strTitle As String
Private originalParent As Long ' Store original parent of target program

Private Sub Form_Load()
    strTitle = "My Program" ' Title of the target program window
    parenthwnd = FindWindow(vbNullString, strTitle)
    
    If parenthwnd <> 0 Then
        ' Save the original parent so we can restore it later
        originalParent = GetWindowLong(parenthwnd, GWL_HWNDPARENT)
        
        Dim R As Long
        R = SetWindowLong(parenthwnd, GWL_HWNDPARENT, Me.hWnd)
        
        ' Keep target program active
        SetForegroundWindow(parenthwnd)
    End If
End Sub

' Handle window messages to detect target program close
Private Sub Form_WndProc(ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long)
    If Msg = WM_PARENTNOTIFY Then
        ' Check if the child window (target program) is being destroyed
        If wParam = WM_DESTROY And lParam = parenthwnd Then
            ' Restore the original parent of the target program
            If originalParent <> 0 Then
                SetWindowLong(parenthwnd, GWL_HWNDPARENT, originalParent)
            End If
            
            ' Close the VB6 program
            Unload Me
        End If
    End If
    
    ' Pass unhandled messages to the default handler
    Call DefWindowProc(Me.hWnd, Msg, wParam, lParam)
End Sub

Key Notes for Issue 2: #

• WM_PARENTNOTIFY lets us detect when the target program (now a child window of your VB6 form) is closed. When we receive the WM_DESTROY signal for that window, we trigger our VB6 app to shut down.
• Restoring the original parent cleans up the window hierarchy properly, avoiding any potential system glitches.
• Even if the target program's shutdown code fails to trigger your VB6 app, this message-handling method will independently detect the close and shut down your app automatically.

内容的提问来源于stack exchange，提问作者Codename K