如果我们关机或Logoff时,我们的程序有时会因而无法按正常程序结束,一般我们会在Form的Unload中一段程序结束时要做什么事,但是,如果使用者直接用开始功能菜单的关机,会使UnLoad的部份没有做到,我们现在就想办法来拦截关机(或Logoff)时的信息。
一般来说,关机或Logff后,Windows会传依序送出WM_QUERYENDSESSION的信息给每个Process,如果中间有一个Process不能顺利结束(例如:Word修改后未存档,而出现是否存档,但我们按取消),这时该信息执行的结果会传回False(0),这时Windows也就不再继续送WM_QUERYENDSESSION给下一个Proccess。反之,如果所有的Process都可以顺利结束(也就是每个送出的WM_QUERYENDSESSION都传回True),那才代表以以顺利结束。
不管WM_QUERYENDSESSION最后的结果是可以顺利结束或不能顺利结束,Windows会再送一个WM_ENDSESSION的信息给所有的Process,而wParam的内容便是指出是否可以顺利结束(True菜单可以,False菜单不行,在vb中则CheckwParam
= 0 菜单False ,0菜单True),说到这里大概就知道该如何做啦,程序如下:
’以下在Form Private Sub Form_Load() Dim ret As Long ’记录原来的Window
Procedure的位址 preWinProc = GetWindowLong(Me.hwnd,
GWL_WNDPROC) ’设定form的window Procedure到wndproc ret = SetWindowLong(Me.hwnd,
GWL_WNDPROC, AddressOf wndproc) End Sub
Private Sub Form_Unload(Cancel As Integer) Dim ret As
Long ’取消Message的截取,而使之又只送往原来的Window Procedure ret = SetWindowLong(Me.hwnd,
GWL_WNDPROC, preWinProc) ’这里只是要看看用关机的方式结束程序时,会不会执行到这里 Dim fno As
Long fno = FreeFile Open "c:\tt2" For Append As fno Print #fno,
"ccc" + vbCrLf Close #fno End Sub
’以下在.Bas
Option Explicit
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA"
_ (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As
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
Public Const GWL_WNDPROC = (-4) Public Const WM_ENDSESSION =
&H16 Public Const WM_QUERYENDSESSION = &H11
Public preWinProc As Long
Public Function wndproc(ByVal hwnd As Long, ByVal Msg As Long, _ ByVal
wParam As Long, ByVal lParam As Long) As Long If Msg = WM_QUERYENDSESSION
Then Debug.Print "QryEnd", wParam, lParam Else If Msg = WM_ENDSESSION
Then If wParam 0 Then ’代表将顺利关机或LogOff,这时便得做正常结束程序的操作 Dim fno As
Long Open "c:\ttt" For Output As #1 Print #1,
"hahcccc5" Close #1 End If End If End If ’将之送往原来的Window
Procedure wndproc = CallWindowProc(preWinProc, hwnd, Msg, wParam,
lParam) End Function
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