[求助]有关SetWindowPos函数

echo

下面一段代码是用复选框使窗口置顶的。有些问题想问问大家。

Const HWND_TOPMOST = -1
Private Declare Function SetWindowPos Lib "user32" (ByVal hwnd As Long, ByVal hWndInsertAfter As Long, ByVal x As Long, ByVal y As Long, ByVal cx As Long, ByVal cy As Long, ByVal wFlags As Long) As Long

Private Sub Check1_Click()
Dim lngWindowFront As Long
If Check1.Value = 1 Then '窗口置前
lngWindowFront = SetWindowPos(Me.hwnd, HWND_TOPMOST, 0, 0, 0, 0, 3)
If lngWindowFront = 0 Then
MsgBox "设置失败！", vbInformation, "友情提示"
Else
MsgBox "设置成功！", vbInformation, "友情提示"
End If
Else
lngWindowFront = SetWindowPos(Me.hwnd, -2, 0, 0, 0, 0, 3)
If lngWindowFront = 0 Then
MsgBox "设置失败！", vbInformation, "友情提示"
Else
MsgBox "设置成功！", vbInformation, "友情提示"
End If
End If
End Sub

Const HWND_TOPMOST = -1

为什么要在这里声明常量HWND_TOPMOST = -1呢？
它不是hWndInsertAfter中的值吗？

lngWindowFront = SetWindowPos(Me.hwnd, -2, 0, 0, 0, 0, 3)

而这个-2又代表了什么？

Gue

第2个参数hWndInsertAfter在MSDN里面是这样说的.

1. hWndInsertAfter
   
2.         [in] A handle to the window to precede the positioned window in the Z order. This parameter must be a window handle or one of the following values.
   
3.                 HWND_BOTTOM
   
4.                         Places the window at the bottom of the Z order. If the hWnd parameter identifies a topmost window, the window loses its topmost status and is placed at the bottom of all other windows.
   
5.                 HWND_NOTOPMOST
   
6.                         Places the window above all non-topmost windows (that is, behind all topmost windows). This flag has no effect if the window is already a non-topmost window.
   
7.                 HWND_TOP
   
8.                         Places the window at the top of the Z order.
   
9.                 HWND_TOPMOST
   
10.                         Places the window above all non-topmost windows. The window maintains its topmost position even when it is deactivated.

复制代码

在winuser.h里这些常量定义如下:

1. #define HWND_TOP        ((HWND)0)
   
2. #define HWND_BOTTOM     ((HWND)1)
   
3. #define HWND_TOPMOST    ((HWND)-1)
   
4. #define HWND_NOTOPMOST  ((HWND)-2)

复制代码

echo

#define HWND_TOP        ((HWND)0)
#define HWND_BOTTOM     ((HWND)1)
#define HWND_TOPMOST    ((HWND)-1)
#define HWND_NOTOPMOST  ((HWND)-2)

原来如此，这是已经定义好的。
谢谢朋友/:08