-- 作者:wangxinxin
-- 發布時間:2010-12-14 14:19:11
-- VB中子分類技術實例應用
子分類技術的原理:要先取得原先Window Procedure所在的地址,將之記錄起來,接著設定所有的消息都先轉到我們所寫的消息處理過程上來,我們過濾傳過來的消息,尋找特定的消息進行處理,其余的送回系統,由系統決定如何處理。等到我們不需要再處理這些特定的消息時,便取消消息的截取,即中止子分類過程。它一般需要三個過程:開始截取,消息處理,中止截取. 程序需要一個模塊,在模塊中聲明如下: ’api函數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 ’定義常數Public Const GWL_WNDPROC = (-4) Public Const WM_MOUSEMOVE = &H200 Public Const WM_RBUTTONDOWN = &H204 ’全局變量,存放控件標志性數據Public preWinProc As Long ’本函數就是用來接收子分類時截取的消息的Public Function wndproc(ByVal hwnd As Long, ByVal Msg As Long, _ ByVal wParam As Long, ByVal lParam As Long) As Long ’截取下來的消息存放在msg參數中. if msg=WM_RBUTTONDOWN then ’檢測到鼠標右擊消息,這里就可以加入我們的處理代碼如: msgbox "你好,鼠標右擊消息!" ’需要注意,如果這兒不加入任何代碼,則相當于吃掉了這條消息. else ’如果我們不是我們需要處理的消息,則將之送回原來的程序. wndproc = CallWindowProc(preWinProc, hwnd, Msg, wParam, lParam) endif End Function ’以下代碼在窗體中: ’本例以截取一個combobox控件的消息為例,假設該’控件的名字是:comb1 Private Sub subclass() Dim ret As Long ’記錄Window Procedure的地址 preWinProc = GetWindowLong(comb1.hwnd, GWL_WNDPROC)
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