这个小例子就是用来演示如何得到Windows桌面上处于活动状态的窗口的句柄的。

使用一个Timer控件就可以搞定。在本例中再通过GetWindowText函数来处理得到句柄后的操作。

1。新建一个标准VB6的EXE工程，加入Timer控件
2。API函数的声明

private Declare Function GetForegroundWindow Lib "user32" () as Long
private Declare Function GetWindowText Lib "user32" _
    Alias "GetWindowTextA" (byval hwnd as Long, _
       byval lpString as string, byval cch as Long) as Long

3。在窗体的Load事件中加入代码：

Private Sub Form_Load()
    Timer1.Interval = 100 '设置间隔时间
End Sub

4。在Timer控件中的Timer事件中加入代码：

Private Sub Timer1_Timer()
    Static CurrentHwnd As Long
    Dim ForegroundWindowHwnd As Long
    Dim sText As String * 255
    ForegroundWindowHwnd = GetForegroundWindow
    If ForegroundWindowHwnd = CurrentHwnd Then Exit Sub
    CurrentHwnd = ForegroundWindowHwnd
    If CurrentHwnd <> hwnd Then
        Caption = "ActiveWidow's Caption: " & Left$(sText, GetWindowText(CurrentHwnd, sText, 255))
    Else
        Caption = "ActiveWindow's Caption: Form1"
    End If
End Sub

本程序在Win2000 + Vb6 中调试通过