如何在VB例程中接收自定义消息

如何在VB例程中接收自定义消息 
　　您可以用API函数SetWindowLong指定处理消息的窗口过程（window procedure）为自定义的函数WindowProc，捕获消息ID为WM_USER+1的自定义消息或系统消息。并且，为了保证窗口能正确的响应消息，需要保存原来默认的窗口过程并在自定义函数WindowProc中调用。如下例，在按钮事件中发送自定义消息，WindowProc捕获了窗口大小变化的系统定义消息和用户自定义的消息并显示用户自定义的消息参数wParam：
　　在Moduel中加入以下代码，
　　Option Explicit
　　Private Const GWL_WNDPROC = -4
　　Public Const GWL_USERDATA = (-21)
　　Public Const WM_SIZE = &H5
　　Public Const WM_USER = &H400
　　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 
　　Public 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
　　Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
　　Public Function Hook(ByVal hwnd As Long) As Long
　　Dim pOld As Long
　　‘指定自定义的窗口过程
　　pOld = SetWindowLong(hwnd, GWL_WNDPROC, _
　　AddressOf WindowProc) 
　　‘保存原来默认的窗口过程指针
　　SetWindowLong hwnd, GWL_USERDATA, pOld
　　Hook = pOld
　　End Function
　　Public Sub Unhook(ByVal hwnd As Long, ByVal lpWndProc As Long)
　　Dim temp As Long
　　注释：Cease subclassing.
　　temp = SetWindowLong(hwnd, GWL_WNDPROC, lpWndProc)
　　End Sub
　　Function WindowProc(ByVal hw As Long, ByVal uMsg As Long, _
　　ByVal wParam As Long, ByVal lParam As Long) As Long
　　If uMsg = WM_SIZE Then
　　‘处理WM_SIZE消息
　　MsgBox "SIZE"
　　End If
　　If uMsg = WM_USER + 1 Then
　　MsgBox wParam
　　End If
　　Dim lpPrevWndProc As Long
　　‘查询原来默认的窗口过程指针
　　lpPrevWndProc = GetWindowLong(hw, GWL_USERDATA)
　　‘调用原来的窗口过程
　　WindowProc = CallWindowProc(lpPrevWndProc, hw, uMsg,wParam, lParam)
　　End Function
　　在Form中加入以下代码：
　　Dim wParam As Long
　　Dim lParam As Long
　　Dim lResult As Long
　　Private Sub Command1_Click()
　　wParam = 12345
　　lResult = SendMessage(Me.hwnd, WM_USER + 1, wParam, lParam)
　　End Sub
　　Private Sub Form_Load()
　　Me.Tag = Hook(Me.hwnd)
　　End Sub
　　Private Sub Form_Unload(Cancel As Integer)
　　Unhook Me.hwnd, Me.Tag
　　End Sub
　　在VB中用自定义过程捕获并处理消息的详细信息和例子请参考：
　　Q170570 HOWTO: Build a Windows Message Handler with AddressOf in Visual
　　http://support.microsoft.com/support/kb/articles/q170/5/70.asp
　　Q168795 HOWTO: Hook Into a Window注释：s Messages Using AddressOf
　　http://support.microsoft.com/support/kb/articles/q168/7/95.asp