Switching forms in vb.net - vb.net

Question

I am a volunteer for the National Park Service trying to convert an interactive display originally created 20 years ago in a language called ToolBook into Visual Basic. The program consists of several projects under a single solution. The starting project, called "MainMenu", can be thought of as a library, with buttons that bring up “books.” The project called Geology is an example “book” and GeologyMenu can be thought of as the index of a book. The buttons on GeologyMenu connect to “chapters” that explain and show examples of geologic processes in the park. The “chapters” are within the project “Geology” and work fine within the project. All forms used in the program have timers that allow the program to re-set itself to MainMenu when not in use.
In a previous post, with the help of Idle Mind (thank you again), the following code for works fine for going from MainMenu to GeologyMenu and in the reverse direction as long as no button is pushed on GeologyMenu. However, if I go to a “chapter” I can no longer get back to the MainMenu from the GeologyMenu. Here is the relevant code:
MainMenu
Public Class frmMainMenu
Private Sub BtnGeology_Click(sender As Object, e As EventArgs) Handles btnGeology.Click
Dim formNew As New Geology.frmGeologyMenu
AddHandler formNew.FormClosed, AddressOf formNew_FormClosed
TimerMain.Stop()
formNew.Show()
Me.Hide()
End Sub
Private Sub formNew_FormClosed(Sender As Object, e As FormClosedEventArgs)
lblTime.Text = 8
TimerMain.Start()
Me.Show()
End Sub
GeologyMenu
Public Class frmGeologyMenu
Public Sub frmGeologyMenu_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
lblTime.Text = 6
TimerGeologyMenu.Enabled = True
Me.Show()
End Sub
Private Sub BtnErosion_Click(sender As Object, e As EventArgs) Handles btnErosion.Click
TimerGeologyMenu.Stop()
frmErosionP01.Show()
Me.Hide()
End Sub
The code below for takes the viewer to the Erosion “chapter”
Private Sub BtnErosion_Click(sender As Object, e As EventArgs) Handles btnErosion.Click
TimerGeologyMenu.Stop()
frmErosionP01.Show()
Me.Hide()
End Sub
Erosion “Chapter” . This is the code for the button on every form in Erosion that takes the program back to GeologyMenu
Public Class frmErosionP02
Private Sub BtnGeologyMenu_Click(sender As Object, e As EventArgs) Handles btnGeologyMenu.Click
My.Computer.Audio.Stop()
frmGeologyMenu.lblTime.Text = 10
frmGeologyMenu.TimerGeologyMenu.Enabled = True
frmGeologyMenu.Show()
Me.Close()
End Sub
The code for forms within Erosion takes me back to GeologyMenu, but then MainMenu won’t show when I close GeologyMenu and I don’t understand why or how to fix it. Thank you in advance for your help!

Answer 1

Simply, pass the previous menu/Form to the new one in a parameterized constructor and keep it in a class variable, then handle the Form.Closed event of the new menu to show the previous one.
Example for the relevant code:
Public Class frmMainMenu
Inherits Form
Private Sub BtnGeology_Click(sender As Object, e As EventArgs) Handles btnGeology.Click
Dim formNew As New frmGeologyMenu(Me)
Me.Hide()
formNew.Show()
End Sub
End Class
Public Class frmGeologyMenu
Inherits Form
Private PreviousMenu As Form
Private Sub New()
InitializeComponent()
'...
End Sub
Sub New(prevMenu As Form)
Me.New()
PreviousMenu = prevMenu
AddHandler FormClosed,
Sub(s, e)
PreviousMenu.Show()
End Sub
End Sub
Private Sub BtnErosion_Click(sender As Object, e As EventArgs) Handles btnErosion.Click
Dim frmErosion As New frmErosionP02(Me)
Me.Hide()
frmErosion.Show()
End Sub
End Class
Public Class frmErosionP02
Inherits Form
Private PreviousMenu As Form
Private Sub New()
InitializeComponent()
'...
End Sub
Public Sub New(prevMenu As Form)
Me.New()
PreviousMenu = prevMenu
AddHandler FormClosed,
Sub(s, e)
PreviousMenu.Show()
End Sub
End Sub
End Class