Flash a Window in the TaskBar (Win 98/2000)

Category:

System/API

Type:

Snippets

Difficulty:

Intermediate

Author:

Intelligent Solutions Inc.

Version Compatibility:

More information:

This snippet shows you how to use the FlashWindowEx API function, which flashes a window in the taskbar to notify a user of a siginficant event in a program. See the comments for more details.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
Option Explicit Private Type FLASHWINFO cbSize As Long Hwnd As Long dwFlags As Long uCount As Long dwTimeout As Long End Type Private Const FLASHW_TRAY = 2 Private Declare Function LoadLibrary Lib "kernel32" _ Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long Private Declare Function GetProcAddress Lib "kernel32" _ (ByVal hModule As Long, ByVal lpProcName As String) As Long Private Declare Function FreeLibrary Lib "kernel32" _ (ByVal hLibModule As Long) As Long Private Declare Function FlashWindowEx Lib "user32" _ (FWInfo As FLASHWINFO) As Boolean

Code:

Public Sub FlashWindow(Hwnd As Long, _
  Optional NumberOfFlashes As Integer = 5)
'***************************************************
'Purpose: Flashes a Window in the taskbar in order to notify
'a user of an event within a program

'Parameters: Hwnd=hwnd of frm to flash
             'NumberofFlashes = Number of times to
               'flash

'Notes: WINDOWS 98 OR 2000 is REQUIRED

'Uses FlashWindowEx API, which  substitutes
'for bringing you window to the foreground
'obtrusively (e.g., on startup or when siginficant
'event occurs in your program) Windows 98/2000 no
'longer permits this

'Example:

'FlashWindow me.hwnd

'***************************************************
'Prevent Errors by checking if
'the API function is available on the
'Current OS

If Not APIFunctionPresent("FlashWindowEx", "user32") _
   Then Exit Sub

Dim bRet As Boolean
Dim udtFWInfo As FLASHWINFO

With udtFWInfo
   .cbSize = 20
   .Hwnd = Hwnd
   .dwFlags = FLASHW_TRAY
   .uCount = NumberOfFlashes 'flash window 5 times
   .dwTimeout = 0
End With

bRet = FlashWindowEx(udtFWInfo)
End Sub

Private Function APIFunctionPresent(ByVal FunctionName _
   As String, ByVal DllName As String) As Boolean

'USAGE:
'Dim bAvail as boolean
'bAvail = APIFunctionPresent("GetDiskFreeSpaceExA", "kernel32")

Dim lHandle As Long
    Dim lAddr  As Long

lHandle = LoadLibrary(DllName)
    If lHandle <> 0 Then
        lAddr = GetProcAddress(lHandle, FunctionName)
        FreeLibrary lHandle
    End If
    
    APIFunctionPresent = (lAddr <> 0)

End Function