 For
those developers who may prefer to use the API over VB's intrinsic timer
control, this page shows how to cause an application to flash its window
(on screen or in the taskbar) using FlashWindow. In addition, it
details how to create a timer using the SetTimer API, and how to respond
to the TimerProc callback message raised each time the API's timer's
elapsed interval expires.
Flashing a window means changing the appearance of its caption bar as if
the window were changing from inactive to active status, or vice versa.
(An inactive caption bar changes to an active caption bar; an active
caption bar changes to an inactive caption bar.) Typically, a window is
flashed to inform the user that the window requires attention but that it
does not currently have the keyboard focus. The FlashWindow function
flashes the window only once; for repeated flashing, the application
requires calling via a VB or system timer.
When FlashWindow's bInvert parameter is TRUE, the window is flashed from
one state to the other. If it is FALSE, the window is returned to its
original state (either active or inactive). When an application is
minimized and this parameter is TRUE, the taskbar window button flashes
active/inactive. If it is FALSE, the taskbar window button flashes
inactive, meaning that it does not change colors. It flashes, as if it
were being redrawn, but it does not provide the visual invert clue to the
user.
With SetTimer, the nIDEvent member specifies a non-zero timer identifier.
If the hwnd parameter of SetTimer is null, nIDEvent is ignored. If hwnd
is non-null and the window specified by hwnd already has a timer with the
value nIDEvent, then the existing timer is replaced by the new timer.
When SetTimer replaces a timer, the timer is reset. Therefore, a message
will be sent after the current time-out value elapses, but the previously
set time-out value is ignored. The hwnd parameter specifies the
handle to the window to be associated with the timer --- this window must
be owned by the calling thread. If this parameter is null (0&) no
window is associated with the timer and the nIDEvent parameter is
ignored. |
Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright ©1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
' applications, but you may not reproduce
' or publish this code on any web site,
' online service, or distribute as source
' on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private tmrRunning As Boolean
Private Const nEventID As Long = 999
Private Const WM_TIMER = &H113
Private Declare Function FlashWindow Lib "user32" _
(ByVal hwnd As Long, _
ByVal bInvert As Long) As Long
Private Declare Function SetTimer Lib "user32" _
(ByVal hwnd As Long, _
ByVal nIDEvent As Long, _
ByVal uElapse As Long, _
ByVal lpTimerFunc As Long) As Long
Private Declare Function KillTimer Lib "user32" _
(ByVal hwnd As Long, _
ByVal nIDEvent As Long) As Long
Public Sub FlashBegin(ByVal hwnd As Long, ByVal Frequency As Long)
If Not tmrRunning Then
If Frequency > 0 Then
Call SetTimer(hwnd, nEventID, Frequency, AddressOf TimerProc)
tmrRunning = True
End If
End If
End Sub
Public Sub FlashEnd(ByVal hwnd As Long)
If tmrRunning = True Then
Call FlashWindow(hwnd, False)
Call KillTimer(hwnd, nEventID)
tmrRunning = False
End If
End Sub
Public Function TimerProc(ByVal hwnd As Long, _
ByVal uMsg As Long, _
ByVal idEvent As Long, _
ByVal dwTime As Long) As Long
Select Case uMsg
Case WM_TIMER
If idEvent = nEventID Then
Call FlashWindow(hwnd, True)
End If
Case Else
End Select
End Function |
Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright ©1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
' applications, but you may not reproduce
' or publish this code on any web site,
' online service, or distribute as source
' on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Sub Command1_Click()
Call FlashBegin(Me.hwnd, Val(Combo1.List(Combo1.ListIndex)))
Combo1.Enabled = False
Command1.Enabled = False
End Sub
Private Sub Command2_Click()
Call FlashEnd(Me.hwnd)
Command1.Enabled = True
Combo1.Enabled = True
End Sub
Private Sub Form_Load()
With Combo1
.AddItem "50"
.AddItem "100"
.AddItem "250"
.AddItem "500"
.AddItem "1000"
.ListIndex = 2
End With
Command1.Caption = "Begin Flash"
Command2.Caption = "Stop Flash"
End Sub |
