CODEWITHSUNDEEP
.netvb.netwinformsmethodsdelegates
ElektroStudios
ElektroStudios

Reputation: 20474

Capturing when a method is called?

( First of all sorry because I don't know how to properly name this question. )

I need to perform some kind of operations when I call this from a Button in the GUI:

Listview1.Items.Add(LVItem)

The thing is that I need to do it from other Class, I mean not inheriting the ListView to raise an own ItemIsAdded Event etc...

Then is this possibly to do?

I will show an example to understande me better:

I have the Form1 class:

Public Class Form1

Public WithEvents _undoManager As UndoManager

Private Sub Form1_Load(sender As Object, e As EventArgs) _
Handles MyBase.Load

    _undoManager = New UndoManager(Listview1)

End Sub

Private Sub Button_AddItem_Click(sender As Object, e As EventArgs) _
Handles Button_AddItem.Click

    Listview1.Items.Add(LVItem)

End Sub

End Class

And the UndoManager Class:

Public Class UndoManager

    Delegate Sub AddDelegate(item As ListViewItem)

    Private Shared LV As ListView

    Private Shared ListView_Add_Method = New AddDelegate(AddressOf LV.Items.Add)

    Public Sub New(ByVal ListView As ListView)
        LV = ListView
    End Sub


    ' Here code to capture when the delegate method is called...

    private sub blahblahblah() handles ListView_Add_Method.IsCalled
      ' blah blah blah
    end sub    

End Class

Then the UndoManager Class need to capture when I call Listview1.Items.Add(LVItem) in the Form1 Class to perform some kind of operations and then add the item (really no mather if the operation runs before or runs after the Items.Add() method is called).

Upvotes: 0

Views: 73

Answers (1)

Ňɏssa Pøngjǣrdenlarp
Ňɏssa Pøngjǣrdenlarp

Reputation: 38895

you already have an ItemAdded event - what you are missing is a way for Undo Manager to watch for those events. One way is to just add a hander to a class which will watch for that event. For instance, for text watcher:

Friend Overrides Function Watcher(ByVal ctl As Control) As Boolean

    ' can also be ComboBox, DateTimePicker etc
    If TypeOf Ctl is TextBox Then
          AddHandler ctl.Enter, AddressOf _Enter
          AddHandler ctl.Leave, AddressOf _Leave
            Return True

        Case Else
            Return False

    End Select

End Function

_enter gets the BeforeText _leave compares it to the text now. if there is a change, then begin to make an undoaction. In your case, you only need to monitor ctl.ItemAdded and ctl.ItemRemoved to make an event (no need to compare). Being only a little clever you should be able to easily create Item, Label and Check Undo actions based on the event being watched.

The watchers (that other UndoManager called them Monitors) is the one that creates undo actions:

Private Sub _Leave(ByVal sender As System.Object, ByVal e As System.EventArgs)
    Dim NewText As String = CType(sender, Control).Text

    If _Text <> NewText Then
        MyBase.OnNewAction(sender, _ 
           New AddActionArgs(UndoManager.UnDoReDo.UnDo, _
           New TextUndo(sender, _Text)))
    End If
End Sub

Upvotes: 1

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