programing vb.net, Textbox in second form will not update - vb.net

Question

I am trying to create a timer that will countdown from the specified time.
The user enters a time and clicks a button.
The button click opens a second form that has a timer in it.
Every time the timer ticks, the time decreases and the time left is displayed in a textbox on form2 (textbox.text = timeLeft).
However, the textbox will never actually update. It remains blank, and the only time that assigning a new value to the .text property will actually work is if I raise an event (for example clicking a button that will change the .text property of the textbox)
*Here is the code for the timer class
Public Class CountdownTimer
Private timeAtStart As Integer
Private timeLeft As Integer
Public Sub StartTimer(ByVal time As Integer)
timeAtStart = time
timeLeft = timeAtStart
Timer1.Enabled = True
End Sub
Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles Timer1.Tick
If timeLeft > 0 Then
timeLeft = timeLeft - 1
txtTimeLeft.Text = timeLeft.ToString
Else
Timer1.Stop()
txtTimeRemaining.Text = "Time!"
txtTimeRemaining.ForeColor = Color.Red
End If
End Sub
End Class
And here is how I call it:
Dim timer As New CountdownTimer
timer.Show()
CountdownTimer.StartTimer(CInt(txtSetTime.Text))

Answer 1

Your code is calling the (form) class not the instance, and I cant see where Timer1 is properly referenced for an independant reusable class. Here is one way to implement a CountDown class that will work with other forms....
Friend Class CountdownTimer
Private timeAtStart As Integer
Private timeLeft As Integer
Private WithEvents Timer1 As New Timer
Private txtTimeLeft as TextBox
Public Sub New(TargetTB as TextBox)
txtTimeLeft= TargetTB
End Sub
Public Sub StartTimer(ByVal time As Integer, timeLength as Integer)
timeAtStart = time
timeLeft = timeLength
Timer1.Enabled = True
End Sub
Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs)_
Handles Timer1.Tick
' just dislaying time left
If timeLeft > 0 Then
timeLeft = timeLeft - 1
txtTimeLeft.Text = timeLeft.ToString
Else
Timer1.Stop()
txtTimeLeft.Text = "Time!"
txtTimeLeft.ForeColor = Color.Red
End If
End Sub
End Class
How to use it:
Dim CountDn As New CountdownTimer(frm.TextBoxToUse)
' use the INSTANCE name not the class name!!!!
'CountdownTimer.StartTimer(CInt(txtSetTime.Text))
CountDn.StartTimer(CInt(txtSetTime.Text))

Answer 2

If it displays the result after the timer has completed, i think you should use the
Application.DoEvents()
method to see the update immediately. It actually works with Windows Forms. What have you tried, so i can help further

Answer 3

You do realize that when you are counting down you are setting a different textbox than when it is complete, right?
txtTimeLeft.Text
VS
txtTimeRemaining.Text
Note: Timers run on the same thread as the UI so if you computer (or program) gets busy, the timer will NOT tick at exact intervals. If you are worried about small variances in your timer, you should compare the difference of your computer time during each tick event to determine how much time had passed.
Dim TS = TimeSpan = Now.Subtract(StartingTime)

Answer 4

Try refreshing the text boxes after each update:
So after
txtTimeLeft.Text = timeLeft.ToString
Add
txtTimeLeft.Refresh

Answer 5

This is your problem:
Dim timer As New CountdownTimer
timer.Show()
CountdownTimer.StartTimer(CInt(txtSetTime.Text))
You instantiate a new object called timer, but then start the timer on the CountdownTimer object
You need to change your code to this:
Dim timer As New CountdownTimer
timer.Show()
timer.StartTimer(CInt(txtSetTime.Text))