Wait a few microseconds and update the screen

Question

I have 4 labels, that must change to bold after waiting 500ms each.

I've tried to use this function:

       LabelUpdater(lblIF); //to bold
       Thread.Sleep(500);
       LabelUpdater(lblIF); //to regular again
       LabelUpdater(lblID); //to bold
       Thread.Sleep(500);
       LabelUpdater(lblID); //to regular again


    private void LabelUpdater(Label labelActual)
    {
        if (labelActual.Font.Bold)
        {
            Console.WriteLine("Regular - " + DateTime.Now);
            labelActual.Font = new Font(labelActual.Font, FontStyle.Regular);
        }
        else
        {
            Console.WriteLine("Bold- " + DateTime.Now);
            labelActual.Font = new Font(labelActual.Font, FontStyle.Bold);
        }
    }

But if I try to run this program, nothing changes. If I just set to bold, everything turn bold in the end of execution.

To get working, i needed to use this:

       LabelUpdater(lblIF); 
       Thread.Sleep(500);
       Application.DoEvents(); //here
       LabelUpdater(lblIF); 
       LabelUpdater(lblID); 
       Thread.Sleep(500);
       Application.DoEvents(); //here
       LabelUpdater(lblID);

Not sure why, i just tried and worked! :D

The human eye and brain can only see changes of e.g. hundred of *milli*-seconds! And you probably need to use timer callbacks. — Basile Starynkevitch, Nov 15 '13 at 17:38
Sleep takes time in milliseconds, so I think the micro was a typo. Anyway, because of how WinForms paints itself, the `Thread.Sleep` calls are probably on the graphics thread which causes the graphics to freeze-up and the controls won't get re-painted until after they've been reverted back anyway. — Anthony, Nov 15 '13 at 17:40
I already managed to get working with `Application.DoEvents();` — Nicke Manarin, Nov 15 '13 at 21:05

Sudhakar Tillapudi · Answer 1 · 2013-11-15T17:45:43.367

you could use Timer Control instead of using Thread.Sleep() as it blocks the main UI.

Step1: Add Timer Control to your Windows Form.

Step2: Set the Interval property of Timer control to 500(Ex:1000 milliseconds = 1 sec)

Step4: Set the Enabled Property to True

Step5: Handle the Tick Event of Timer control as below:

private void timer1_Tick(object sender, EventArgs e)
        {
          LabelUpdater(lblIF); //to bold
        }

Jodrell · Accepted Answer · 2013-11-15T17:56:34.990

1

It sounds like your code is running on the main GUI thread, is it in a button click handler?

The events that you fire in your code are not processed until the current handler has finished executing.

Try running your code on a background thread or, in resposne to a timer. Note that you'll need to handle cross-thread calls to the GUI.

Task.StartNew(BackgroundLabelToggle, Label[] {  lblIF, lblID });

private static void BackgroundLabelToggle(Label[] labels)
{
   var a = labels[0];
   var b = labels[1];

   a.Invoke(LabelUpdater, a); //to bold
   Thread.Sleep(500);
   a.Invoke(LabelUpdater, a); //to regular again
   b.Invoke(LabelUpdater, b); //to bold
   Thread.Sleep(500);
   b.Invoke(LabelUpdater, b); //to regular again
}

edited Nov 15 '13 at 17:56

answered Nov 15 '13 at 17:42

Jodrell

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Yes, a button click handler. – Nicke Manarin Nov 15 '13 at 21:03
I did something smaller, just added `Application.DoEvents();` after the `Thread.Sleep();` – Nicke Manarin Nov 15 '13 at 21:12
1

i don't think it is a Good Patrice to use Appliation.DoEvents(), please check this http://stackoverflow.com/questions/5181777/use-of-application-doevents/5183623#5183623 – Sudhakar Tillapudi Nov 16 '13 at 02:09

Wait a few microseconds and update the screen

2 Answers2