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答案：' 新建一个 ActiveX DLL 工程，名称 SmartSubClassLib
' 以下代码放在标准模块里，模块名 mSmartSubClass
' ----------------------------------------------------
' Module mSmartSubClass
'
' Version... 1.0
' Date...... 24 April 2001
'
' Copyright (C) 2001 Andr閟 Pons (andres@vbsmart.com)
' ----------------------------------------------------
'API declarations:
Option Explicit
Public Const SSC_OLDPROC = "SSC_OLDPROC"
Public Const SSC_OBJADDR = "SSC_OBJADDR"
Private Declare Function GetProp Lib "user32" Alias "GetPropA" ( _
ByVal hWnd As Long, _
ByVal lpString As String) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
Destination As Any, _
Source As Any, _
ByVal Length As Long)
'
' Function StartSubclassWindowProc()
'
' This is the first windowproc that receives messages
' for all subclassed windows.
' The aim of this function is to just collect the message
' and deliver it to the right SmartSubClass instance.
'
Public Function SmartSubClassWindowProc( _
ByVal hWnd As Long, _
ByVal uMsg As Long, _
ByVal wParam As Long, _
ByVal lParam As Long) As Long
Dim lRet As Long
Dim oSmartSubClass As SmartSubClass
'Get the memory address of the class instance...
lRet = GetProp(hWnd, SSC_OBJADDR)
If lRet <> 0 Then
'oSmartSubClass will point to the class instance
'without incrementing the class reference counter...
CopyMemory oSmartSubClass, lRet, 4
'Send the message to the class instance...
SmartSubClassWindowProc = oSmartSubClass.WindowProc(hWnd, _
uMsg, wParam, lParam)
'Remove the address from memory...
CopyMemory oSmartSubClass, 0&, 4
End If
End Function
' 以下代码放在类模块里，模块名 SmartSubClass
' ----------------------------------------------------
' Class SmartSubClass
'
' Version... 1.0
' Date...... 24 April 2001
'
' Copyright (C) 2001 Andr閟 Pons (andres@vbsmart.com)
' ----------------------------------------------------
Option Explicit
'Public event:
Public Event NewMessage( _
ByVal hWnd As Long, _
ByRef uMsg As Long, _
ByRef wParam As Long, _
ByRef lParam As Long, _
ByRef Cancel As Boolean)
'Private variables:
Private m_hWnds() As Long
'API declarations:
Private Const GWL_WNDPROC = (-4)
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" ( _
ByVal hWnd As Long, _
ByVal nIndex As Long) 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 CallWindowProc Lib "user32" Alias "CallWindowProcA" ( _
ByVal lpPrevWndFunc As Long, _
ByVal hWnd As Long, _
ByVal Msg As Long, _
ByVal wParam As Long, _
ByVal lParam As Long) As Long
Private Declare Function GetProp Lib "user32" Alias "GetPropA" ( _
ByVal hWnd As Long, _
ByVal lpString As String) As Long
Private Declare Function SetProp Lib "user32" Alias "SetPropA" ( _
ByVal hWnd As Long, _
ByVal lpString As String, _
ByVal hData As Long) As Long
Private Declare Function RemoveProp Lib "user32" Alias "RemovePropA" ( _
ByVal hWnd As Long, _
ByVal lpString As String) As Long
Private Declare Function IsWindow Lib "user32" ( _
ByVal hWnd As Long) As Long
'
' Function SubClassHwnd
'
' This is the core function in this class.
' You can use it to both subclass and unsubclass a window.
' Once a window is subclassed the event NewMessage will
' be raised every time a message is sent to the window.
'
Public Function SubClassHwnd(ByVal hWnd As Long, _
ByVal bSubClass As Boolean) As Boolean
Dim lRet As Long
lRet = 0
'Make sure that hWnd is a valid window handler...
If IsWindow(hWnd) Then
If bSubClass Then
'We are subclassing a window...
'Make sure that the window wasn't already subclassed...
If GetProp(hWnd, SSC_OLDPROC) = 0 Then
'Now we subclass the window by changing its windowproc
lRet = SetWindowLong(hWnd, GWL_WNDPROC, _
AddressOf SmartSubClassWindowProc)
'Check if we've managed to subclass...
If lRet <> 0 Then
'Store the old windowproc and the memory
' address of this class...
SetProp hWnd, SSC_OLDPROC, lRet
SetProp hWnd, SSC_OBJADDR, ObjPtr(Me)
'Add the window to an internal list of
' subclassed windows...
pAddHwndToList hWnd
End If
End If
Else
'We are unsubclassing a window...
'Get the old windowproc...
lRet = GetProp(hWnd, SSC_OLDPROC)
If lRet <> 0 Then
'Unsubclass the window...
lRet = SetWindowLong(hWnd, GWL_WNDPROC, lRet)
End If
'Remove any extra information...
RemoveProp hWnd, SSC_OLDPROC
RemoveProp hWnd, SSC_OBJADDR
'Remove the window from the internal list...
pRemoveHwndFromList hWnd
End If
Else
'If hWnd is not a valid window,
'make sure that there isn't stored garbage...
RemoveProp hWnd, SSC_OLDPROC
RemoveProp hWnd, SSC_OBJADDR
pRemoveHwndFromList hWnd
End If
SubClassHwnd = (lRet <> 0)
End Function
'
' Function WindowProc
'
' This is the link between the windowproc and the class instance.
' Every time SmartSubClassWindowProc receives a window message,
' it will post it to the right class instance.
'
Friend Function WindowProc( _
ByVal hWnd As Long, _
ByVal uMsg As Long, _
ByVal wParam As Long, _
ByVal lParam As Long) As Long
Dim lRet As Long
Dim bCancel As Boolean
bCancel = False
WindowProc = 0
'Raise the event NewMessage...
'This will tell the owner of the class variable that a
'new message is ready to be processed.
'The owner will be able to cancel the message by setting
'the variable bCancel to True.
RaiseEvent NewMessage(hWnd, uMsg, wParam, lParam, bCancel)
'If the event hasn't been canceled by the owner
'we need to send it to the original windowproc
If Not bCancel Then
lRet = GetProp(hWnd, SSC_OLDPROC)
If lRet <> 0 Then
'Send the message to the original windowproc...
WindowProc = CallWindowProc(lRet, hWnd, uMsg, wParam, lParam)
End If
End If
End Function
'
' Every instance of the class mantains an internal
' list of subclassed windows.
'
Private Sub Class_Initialize()
ReDim m_hWnds(0) As Long
End Sub
'
' When the class terminates it makes sure that
' there are no remain
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