Option Explicit

'Transparancy API's
Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hWnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
Private Declare Function UpdateLayeredWindow Lib "user32" (ByVal hWnd As Long, ByVal hdcDst As Long, pptDst As Any, psize As Any, ByVal hdcSrc As Long, pptSrc As Any, crKey As Long, ByVal pblend As Long, ByVal dwFlags As Long) 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 Const GWL_EXSTYLE = (-20)
Private Const LWA_COLORKEY = &H1
Private Const LWA_ALPHA = &H2
Private Const ULW_COLORKEY = &H1
Private Const ULW_ALPHA = &H2
Private Const ULW_OPAQUE = &H4
Private Const WS_EX_LAYERED = &H80000

Public Function isTransparent(ByVal hWnd As Long) As Boolean
On Error Resume Next
Dim Msg As Long
Msg = GetWindowLong(hWnd, GWL_EXSTYLE)
If (Msg And WS_EX_LAYERED) = WS_EX_LAYERED Then
isTransparent = True
Else
isTransparent = False
End If
If Err Then
isTransparent = False
End If
End Function

Public Function MakeTransparent(ByVal hWnd As Long, ByVal Perc As Integer) As Long
Dim Msg As Long
On Error Resume Next

Perc = 100
If Perc < 0 Or Perc > 255 Then
MakeTransparent = 1
Else
Msg = GetWindowLong(hWnd, GWL_EXSTYLE)
Msg = Msg Or WS_EX_LAYERED
SetWindowLong hWnd, GWL_EXSTYLE, Msg
SetLayeredWindowAttributes hWnd, 0, Perc, LWA_ALPHA
MakeTransparent = 0
End If
If Err Then
MakeTransparent = 2
End If
End Function

Public Function MakeOpaque(ByVal hWnd As Long) As Long
Dim Msg As Long
On Error Resume Next
Msg = GetWindowLong(hWnd, GWL_EXSTYLE)
Msg = Msg And Not WS_EX_LAYERED
SetWindowLong hWnd, GWL_EXSTYLE, Msg
SetLayeredWindowAttributes hWnd, 0, 0, LWA_ALPHA
MakeOpaque = 0
If Err Then
MakeOpaque = 2
End If
End Function
''窗体加载时
Private Sub Form_Load()
MakeTransparent Me.hWnd, 20
End Sub

[此贴子已经被作者于2007-3-6 23:55:12编辑过]

二楼的方法好像是半透明吧!下面代码是全透明的窗体.
[CODE]Option Explicit
Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) 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
Const WS_EX_LAYERED = &H80000
Const GWL_EXSTYLE = (-20)
Const LWA_ALPHA = &H2
Const LWA_COLORKEY = &H1
Private Sub Form_Load()
Dim sty As Long
sty = GetWindowLong(Me.hwnd, GWL_EXSTYLE)
sty = sty Or WS_EX_LAYERED
SetWindowLong Me.hwnd, GWL_EXSTYLE, sty
SetLayeredWindowAttributes Me.hwnd, 0, 0, LWA_ALPHA
End Sub[/CODE]

[此贴子已经被作者于2007-3-7 0:04:19编辑过]

[此贴子已经被作者于2007-3-7 20:11:14编辑过]

这个是一窗体慢慢载入的程序（从不可见到完全显示）。。


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 GetWindowLong Lib "user32" _
Alias "GetWindowLongA" _
(ByVal hwnd As Long, _
ByVal nIndex As Long) _
As Long

Private Const GWL_EXSTYLE = (-20)
Private Const LWA_ALPHA As Long = &H2
Private Const WS_EX_LAYERED As Long = &H80000

Private Declare Function SetLayeredWindowAttributes Lib "user32" _
(ByVal hwnd As Long, _
ByVal crKey As Long, _
ByVal bAlpha As Long, _
ByVal dwFlags As Long) _
As Long
Dim i As Long

Private Sub Form_Load()
i = 0
Timer1.Interval = 10
Timer1.Enabled = True
Dim p As Long
p = GetWindowLong(Me.hwnd, GWL_EXSTYLE) '取得当前窗口属性
Call SetWindowLong(Me.hwnd, GWL_EXSTYLE, p Or WS_EX_LAYERED)
'加上一个透明属性
Call SetLayeredWindowAttributes(Me.hwnd, 0, i, LWA_ALPHA)
End Sub

Private Sub Timer1_Timer()
i = i + 8
If i > 255 Then
i = 255
Call SetLayeredWindowAttributes(Me.hwnd, 0, i, LWA_ALPHA)
Timer1.Enabled = False
Else
Call SetLayeredWindowAttributes(Me.hwnd, 0, i, LWA_ALPHA)
End If
End Sub

真的是难
这么多函数啥的太难了
多练习