| 子分类技术的原理：要先取得原先Window Procedure所在的地址，将之记录起来，接着设定所有的消息都先转到我们所写的消息处理过程上来，我们过滤传过来的消息，寻找特定的消息进行处理，其余的送回系统，由系统决定如何处理。等到我们不需要再处理这些特定的消息时，便取消消息的截取，即中止子分类过程。它一般需要三个过程:开始截取,消息处理,中止截取. 程序需要一个模块，在模块中声明如下： 'API函数Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _ (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) A s Long Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _ (ByVal hwnd As Long, ByVal nIndex As Long) As Long 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 '定义常数Public Const GWL_WNDPROC = (-4) Public Const WM_MOUSEMOVE = &H200 Public Const WM_RBUTTONDOWN = &H204 '全局变量,存放控件标志性数据Public preWinProc As Long '本函数就是用来接收子分类时截取的消息的Public Function wndproc(ByVal hwnd As Long, ByVal Msg As Long, _ ByVal wParam As Long, ByVal lParam As Long) As Long '截取下来的消息存放在msg参数中. if msg=WM_RBUTTONDOWN then '检测到鼠标右击消息,这里就可以加入我们的处理代码如: msgbox "你好,鼠标右击消息!" '需要注意,如果这儿不加入任何代码,则相当于吃掉了这条消息. else '如果我们不是我们需要处理的消息,则将之送回原来的程序. wndproc = CallWindowProc(preWinProc, hwnd, Msg, wParam, lParam) endif End Function '以下代码在窗体中: '本例以截取一个combobox控件的消息为例,假设该'控件的名字是:comb1 Private Sub subclass() Dim ret As Long '记录Window Procedure的地址 preWinProc = GetWindowLong(comb1.hwnd, GWL_WNDPROC) '开始截取消息,并将消息交给wndproc过程处理. ret = SetWindowLong(comb1.hwnd, GWL_WNDPROC, AddressOf wndproc) End Sub Private Sub EndSubclass() Dim ret As Long '取消消息截取，结束子分类过程. ret = SetWindowLong(comb1.hwnd, GWL_WNDPROC, preWinProc) End Sub '当要截取其它控件的消息时,只需要将subclass与EndSubclass过程中的comb1.h wnd换成该控件的控件.hwnd即可. '调试过程中注意存盘,因为如果一时不慎会造成死机 |
