I have a toolbar with the Cut, Copy, Paste, Delete icons on it, and I need to know when the current control changes so I can enable or disable an toolbaritem depending on the type of the current control. What is the best way of doing this?
Well you have events - so that depending upon you design you may want to look at the lostfocus / gotfocus event for the controls. Which means that as you tab around the form selecting controls a different control will get the focus.
Only one control will have the focus at any one time.
So, tying it all together, you might handle the GotFocus event of each control and then test to see if, based on the type of the current control, the menu items should be enabled.
You'll probably want a helper function that will attach all of the event handlers for you. This can be done very easily with a little recursive subroutine. Just call this sub at form load. Bear in mind that if you add any new controls during runtime you'll want to attach their handlers when they are created (I wouldn't call this sub more than once).
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'Make a call to the handle attaching sub
Me.AttachFocusHandler(Me.Controls)
End Sub
'Create the recursive sub to add GotFocus handlers
'Be sure to fully qualify the ControlCollection; this
'is one place where imported namespaces will trip you up
Private Sub AttachFocusHandler(ByVal ctrls As System.Windows.Forms.Control.ControlCollection)
'Loop through each control in the collection
For Each ctrl As Control In ctrls
'Add the handler for the GotFocus event
AddHandler ctrl.GotFocus, AddressOf ControlGotFocus
'Call the sub again with this control's
'control collection (recursion)
Me.AttachFocusHandler(ctrl.Controls)
Next
End Sub
'Handle the GotFocus even for each control
Private Sub ControlGotFocus(ByVal sender As Object, ByVal e As System.EventArgs)
'Declare a variable to hold the value that
'the MenuItems' Enabled property will be set to
Dim en As Boolean = False
'Check to see of the Control that got
'focus is a TextBox
If sender.GetType Is GetType(TextBox) Then
'If so, enable the menu items
en = True
End If
'Set the menu items' enabled property
'to the determined value
Me.CopyToolStripMenuItem.Enabled = en
Me.CutToolStripMenuItem.Enabled = en
Me.PasteToolStripMenuItem.Enabled = en
End Sub
End Class
That should get you started. Good luck!
