Windows提供的鼠标移出消息有时候很有用，但是VB6中没有把这个事件封装给我们。
但是我们仍然可以使用子类化技术实现他，下面的代码就是一个简单的例子来处理Windows的
WM_MOUSELEAVE消息的，我演示的是鼠标移出一个Button时的情形。
1.加入一个模块，专门用来处理子类函数：
Option Explicit
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'Copyright 2002 40Star, All Rights Reserved.
'
'E-Mail ：40Star@163.com
'Distribution：你可以完全自由随便的使用这段代码，不管你用于任何目的
' 程序在于交流和学习
' 如有任何BUG请和我联系
'
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Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hwnd As Long, ByVal wMsg As Long, _
ByVal wParam As Long, lParam As String) As Long
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
Const GWL_WNDPROC = (-4&)
Dim PrevWndProc&
Private Const WM_DESTROY = &H2
Public Declare Function TrackMouseEvent Lib "user32" (lpEventTrack As TRACKMOUSEEVENTTYPE) As Long
Public Const TME_CANCEL = &H80000000
Public Const TME_HOVER = &H1&
Public Const TME_LEAVE = &H2&
Public Const TME_NONCLIENT = &H10&
Public Const TME_QUERY = &H40000000
Private Const WM_MOUSELEAVE = &H2A3&
Public Type TRACKMOUSEEVENTTYPE
cbSize As Long
dwFlags As Long
hwndTrack As Long
dwHoverTime As Long
End Type
Public bTracking As Boolean
Dim evtTrack As TRACKMOUSEEVENTTYPE
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Private Function SubWndProc(ByVal hwnd As Long, ByVal Msg As Long, _
ByVal wParam As Long, ByVal lParam As Long) _
As Long
If Msg = WM_DESTROY Then Terminate (hwnd)
'处理鼠标移出消息
If Msg = WM_MOUSELEAVE Then
bTracking = False
Form1.Print "The mouse left the form!"
End If
SubWndProc = CallWindowProc(PrevWndProc, hwnd, Msg, wParam, lParam)
End Function
Public Sub Init(hwnd As Long)
PrevWndProc = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf SubWndProc)
End Sub
Public Sub Terminate(hwnd As Long)
Call SetWindowLong(hwnd, GWL_WNDPROC, PrevWndProc)
End Sub
' -- 模块结束 -- '
2. 窗体中处理需要加入的代码：
Option Explicit
Private Sub Command1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If bTracking = False Then
bTracking = True
Dim ET As TRACKMOUSEEVENTTYPE
'initialize structure
ET.cbSize = Len(ET)
ET.hwndTrack = Command1.hwnd
ET.dwFlags = TME_LEAVE
'start the tracking
TrackMouseEvent ET
End If
End Sub
Private Sub Form_Load()
Call Init(Command1.hwnd)
End Sub
Private Sub Form_Unload(Cancel As Integer)
Call Terminate(Command1.hwnd)
End Sub
此例程在Win2000 + VB6中调试通过
