String array to a label

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I've got a string array and I need to show the contents of it to a single label. It acts like a clock. The thing is I tried with everything I could but I failed. This is the code I've been trying. Its in VB.NET and there is a Thread.Sleep(2000) running to slow down the loop so I can display the contents in a label for 2 seconds. Is that the thing causing the problem? Please help.
Thanks.

VB

Dim j As Integer
For j = 0 To readText.Length
    label.text=readText(j)
    Thread.Sleep(2000)
Next

[Moved to question from an "answer" for OP]
Here is my code it's still not functioning:

VB

Imports System
Imports System.IO
Imports System.Threading

Public Class Form2
Dim readText() As String

Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    Dim path As String = "c:\test.txt"
    readText = File.ReadAllLines(path)

    Dim temp As String
    Dim i As Integer
    Dim rnum As Integer
    Dim r As New Random

    For Each text As String In readText
        rnum = r.Next(0, readText.Length)
        temp = readText(i)
        readText(i) = readText(rnum)
        readText(rnum) = temp
    Next text

    Dim j As Integer
    For j = 0 To readText.Length
        Label1.Text = readText(j)
        Thread.Sleep(2000)
    Next j

End Sub

End Class

Posted 12-Jan-11 3:13am

aroshlakshan

Updated 12-Jan-11 23:48pm

Manfred Rudolf Bihy

v4

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#realJSOP 12-Jan-11 9:37am

Use Add a Comment link under the answer you want to respond to. If you don't do it that way, the person you're responding to won't get a notification that you responded.

Manfred Rudolf Bihy 13-Jan-11 5:49am

Comment from ARopo: What is the problem now?

5 solutions

Solution 9

If you are new at vb.net All above are little bit complex. It would be very easy using a Timer. Threading or sleeping problems will never arise here.
How to do that:
1. Add a timer into your form.
2.Add into proc Form2_Load

VB

Timer1.Enabled = True
Timer1.Interval = 2000
Timer1.Tag=0

3. You set

VB

Dim readText() As String

as global. So no problem. Do not change it.
4. Now:

VB

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
    Try
        Label.Text = readText(Timer1.Tag)
        Timer1.Tag = Timer1.Tag + 1
    Catch ex As Exception
        Timer1.Tag = 0
        Label.Text = readText(Timer1.Tag)
        Timer1.Tag = Timer1.Tag + 1
    End Try
End Sub

Timer has a problem that is it 0~15ms tolerent. I don't know why. May be my pc is slow.

Posted 13-Jan-11 0:22am

Аslam Iqbal

Updated 13-Jan-11 0:26am

v2

Solution 3

Put this just before the Thread.Sleep line:

Application.DoEvents()

This will refresh your label before sending the GUI thread to sleep.

Posted 12-Jan-11 3:25am

_Erik_

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#realJSOP · Accepted Answer · 2011-01-12T03:33:00

Use a BackgroundWorker object to control the display time, and use the Progress event to display the actual data based on the progress value you sentd to the event. The code below is in C#, but converting it to vb shouldn't be a problem.

C#

private void worker_DoWork(object sender)
{
    BackgroundWorker worker = sender as BackgroundWorker;
    int delay = 2000;
    int interval = 100;
    int elapsed = 0;
    int pos = myString.Length;

    while (!worker.CancellationPending)
    {
        if (eplapsed >= delay)
        {
            worker.ReportProgress(pos);  // change label text in the Progress event handler
            pos++;
            elapsed = 0;
            if (pos == myString.Length)
            {
                break;
            }
        }
        Thread.Sleep(interval);
    }
}

Caveat: I typed this without testing it so you may need to tweak it a little. This approach keeps your UI responsive to user input as well, and avoids using DoEvents().

Manfred Rudolf Bihy · Accepted Answer · 2011-01-12T03:22:00

Thread.Sleep(2000) is blocking your UI thread. While the loop is running the GUI will not respond. To manage long running methods you'll have to use a BackgroundWorker and update your GUI control (label in this case) from there. To be able to access the control from the BackgroundWorker you'll have to use Invoke();. See here: http://blogs.msdn.com/b/csharpfaq/archive/2004/03/17/91685.aspx[^].

Or just look at JSOP's answer. That's the way to do it!

Best Regards,
Manfred

ARopo · Accepted Answer · 2011-01-12T03:23:00

To see your label update every 2 seconds you need to process events try something like this:

VB

Dim j As Integer
       For j = 0 To readText.Length
           label.text=readText(j)
           Application.DoEvents()
           Thread.Sleep(2000)
       Next

Detail.

The user interface is updated via events/messages. These events/messages are queued and the processed by the main user interface thread. When you update a label it is usually on the main user interface thread, otherwise you have to update it indirectly with Invoke().

Thread.Sleep(2000) puts the current thread (in this case the main user interface thread) to sleep for 2000 milliseconds. during this time no messages/events can be processed Application.DoEvents() forces all pending messages/events to be processed.

Any thing you do on an event will holdup the message/event processing until you finish unless you start off a new thread or force processing with DoEvents

String array to a label

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