addhandler and addressof

Question

Hi,

if I code so, I get the error: Error    1    'AddressOf' operand must be the name of a method (without parentheses).    D:\Egyeb\OTIS\OTIS\kozos\kozos.vb    36    40    OTIS

Public Sub GreenMessage(ByVal item As BarStaticItem, ByVal szoveg As String)
        item.Caption = szoveg
        item.ImageIndex = 2
        item.Appearance.BackColor = ColorTranslator.FromOle(greenstatusbar)
        My.Computer.Audio.Play(My.Resources.sapmsg, AudioPlayMode.Background)
        tmr.Interval = 500
        AddHandler tmr.Tick, AddressOf tmr_tick(item)
        tmr.Start()
    End Sub
    Private Sub tmr_tick(ByVal item As BarStaticItem)
        item.Appearance.BackColor = ColorTranslator.FromOle(14206908)
        tmr.Stop()
    End Sub

If I delete the argument, I get the error: Error    1    Argument not specified for parameter 'item' of 'Private Sub tmr_tick(item As DevExpress.XtraBars.BarStaticItem)'.    D:\Egyeb\OTIS\OTIS\kozos\kozos.vb    36    40    OTIS

Public Sub GreenMessage(ByVal item As BarStaticItem, ByVal szoveg As String)
        item.Caption = szoveg
        item.ImageIndex = 2
        item.Appearance.BackColor = ColorTranslator.FromOle(greenstatusbar)
        My.Computer.Audio.Play(My.Resources.sapmsg, AudioPlayMode.Background)
        tmr.Interval = 500
        AddHandler tmr.Tick, AddressOf tmr_tick()
        tmr.Start()
    End Sub
    Private Sub tmr_tick(ByVal item As BarStaticItem)
        item.Appearance.BackColor = ColorTranslator.FromOle(14206908)
        tmr.Stop()
    End Sub

So, how would it be the right way?

Answer 1

You cannot add an event handler that does not have the correct matching signature for the event you are handling. A timer.Tick event does not have the following signature.

ByVal item As BarStaticItem

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Answer 2

I just want to clarify further, instead of trying to deviate from the intended signature of an event, instead try making your value public and accessing that value from there, meanwhile, you have to use a sub that has a matching signature of the event you are assigning to it.

Public Class Form1
    Friend WithEvents Timer1 As New Timer
    Public Item As String
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        AddHandler Timer1.Tick, AddressOf Timer1_Tick
    End Sub
    Sub Timer1_Tick(sender As Object, e As EventArgs)

    End Sub
End Class

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Answer 3

Assigning events with AddHandler requires that the arguments of the sub you're attaching an event to has the parameters of the event. Timer.Tick has two parameters, the sender object, and the e eventargs. That's why when you double click a timer in the Designer, you get:

    Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles Timer1.Tick

    End Sub

BarStaticItem is not passed from the Timer.Tick event, which makes it throw an error.

You could overcome it by, for example, making a custom class that holds a timer and an item.

Here's an example, adding a new class MyTimer:

Public Class MyTimer
    Public Tmr As Timer
    Public Item As BarStaticItem

    Sub New(tmr As Timer, item As BarStaticItem)
        Me.Tmr = tmr
        Me.Item = item
        AddHandler tmr.Tick, AddressOf Tmr_Tick
    End Sub

    Private Sub Tmr_Tick(sender As System.Object, e As System.EventArgs)
        Item.Appearance.BackColor = ColorTranslator.FromOle(14206908)
        Tmr.Stop()
    End Sub
End Class

This way you can create a new MyTimer like this:

    Public Sub GreenMessage(ByVal item As BarStaticItem, ByVal szoveg As String)
        item.Caption = szoveg
        item.ImageIndex = 2
        item.Appearance.BackColor = ColorTranslator.FromOle(greenstatusbar)
        My.Computer.Audio.Play(My.Resources.sapmsg, AudioPlayMode.Background)
        tmr.Interval = 500
        Dim tmrItem As New MyTimer(tmr, item)
        tmrItem.Tmr.Start()
    End Sub

I hope you got it and that this helps.

Sincerely yours,
- bilde2910

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Answer 4

Use the Timer's Tag property to hold the item:

  Public Sub GreenMessage(ByVal item As BarStaticItem, ByVal szoveg As String)
    item.Caption = szoveg
    item.ImageIndex = 2
    item.Appearance.BackColor = ColorTranslator.FromOle(greenstatusbar)
    My.Computer.Audio.Play(My.Resources.sapmsg, AudioPlayMode.Background)
    tmr.Tag = item
    tmr.Interval = 500
    AddHandler tmr.Tick, AddressOf tmr_tick()
    tmr.Start()
  End Sub
  Private Sub tmr_tick(sender As Object, e As EventArgs)
    Dim Item As BarStaticItem = DirectCast(tmr.Tag, BarStaticItem)
    item.Appearance.BackColor = ColorTranslator.FromOle(14206908)
    tmr.Stop()
  End Sub